minimum clock speed needed for lcd tft display for sale

Low voltage differential signaling (LVDS, also known as OpenLDI) thin-film transistor (TFT) liquid crystal (LCD) displays typically have a specified resolution and minimum required clock frequency to meet desired resolution. Normally, you will find this information listed in the display data sheet and won’t need to perform any calculations.

However, if you do not yet have access to your display data sheet and only know what resolution you want your system to support, you can estimate what clock frequency you need and determine which serializer/deserializer (SerDes) is appropriate for your application.

%Blanking: The blanking period, or the percentage of time when active video is not being displayed. As shown in Figure 1, it is represented horizontally as horizontal pulse width (HPW), horizontal back porch (HBP) and horizontal front porch (HFP). It is also represented vertically as vertical pulse width (VPW), vertical back porch (VBP) and vertical front porch (VFP).

The values for these blanking parameters are listed in display data sheets. The total blanking period varies from 3% to 39%. If your system uses reduced blanking, then you can estimate %Blanking at 10%. If you are not sure what blanking period your system uses, estimate around 20% and above to be conservative.

Frame rate (or refresh rate):the frequency at which consecutive images (frames) are displayed, and is measured in hertz or frames per second (fps). 60Hz is the most common frame rate, but this value can vary from 24Hz to 70Hz.

Throughput is another metric that you can use to determine whether or not a device will support your desired display resolution. The throughput is the effective payload of video data, and is derived from the required pixel clock frequency and color depth of your system, as shown in Equation 2:

Color depth: For a first-generation SerDes like the SN65LVDS93A, color depth is typically 24-bit red-green-blue (RGB) or 18-bit RGB for single pixel in, single pixel out (SISO) applications, and 48-bit RGB or 36-bit RGB for dual pixel in, dual pixel out (DIDO) applications.

The color depth will determine how many LVDS data lanes your display requires. SerDes serialize data at a rate of 7x the pixel clock frequency on each LVDS data lane. If the color depth is 24-bit RGB, then you will need four LVDS data lanes (there are an additional four bits used for control, which brings the total bit count to 28 bits) and can use a SerDes like the SN65LVDS93A. If the color depth is 18-bit RGB, then you will need three LVDS data lanes (there are an additional 3 bits used for control, which brings the total bit count to 21 bits) and can use a SerDes like the SN74LVDS84A or the SN65LVDS93A.

If the color depth is 48-bit RGB, then you will need eight LVDS data lanes (there are an additional 8 bits used for control, which brings the total bit count to 56 bits) and will need to use a device like the DS90C387 or DS90C189-Q1, which can output as many as eight LVDS data lanes.

When calculating the throughput for DIDO applications, you need to calculate the throughput for the odd pixels and even pixels separately and then add them together. For example, for a 48-bit DIDO application, the total required throughput would be 2 x Pixel Clock x 24.

Since the color depth is 24-bit RGB, you will need four LVDS data lanes. The SN65LVDS93A is a good fit for this application, since it has a pixel clock frequency range of 10MHz to 135MHz. Additionally, the maximum throughput for each LVDS data lane on this device is 135 x 7 = 945Mbps. Because this device has four LVDS data lanes, the total maximum throughput is 945 x 4 = 3780Mbps, which is higher than the minimum required throughput.

So the minimum pixel clock frequency to support a 2048 x 1536 resolution display is 208MHz. However, since this is a 48-bit DIDO application, there are actually two clocks: the frequency is split between them. Each clock must have a frequency of at least 104MHz.

Since the color depth is 48-bit RGB, you will need eight LVDS data lanes. The DS90C387 and DS90C187 are a good fit for this application, since they have a pixel clock frequency range of 32.5MHz to 112MHz (the DS90C387) and 25MHz to 105MHz (the DS90C187) for each channel in DIDO applications. Thus, if you don’t have access to the display data sheet yet, you can still estimate the required pixel clock frequency and throughput to support your desired resolution. If the SerDes does not meet these parameters, data on the display may display incorrectly, or not display at all.

Since the display includes the Ilitek ILI9320 controller, then your interface requirements are much lower, as the microcontroller no longer has to interface directly with the TFT and instead only talks to the controller chip via a simple interface: either SPI, which takes six wires: RS, CS, CLK, MOSI, MISO and RESET. Or you can use an 8080-compatible parallel interface which takes 13 wires: an 8-bit data bus, and RS, CS, WR, RD and RESET. (There are options to use larger data-buses, up to 18 bits, but I don"t recommend that for a low end microcontroller.)

There are two optional interfaces in which the microcontroller generates all of the clock signals (VSYNC, HSYNC and DOTCLK); you don"t want to do that since it would require a high-end controller.

So just about any microcontroller will do, however you need to have enough flash memory to hold whatever static items you want to display; for example if you are going to be displaying text then you will need to allocate arrays to store bitmaps for whatever fonts you will use. Even a small font can take 60KB.

I will use a 3.3v 500mA power supply connected to a lipo battery, probably with or maybe without a over discharge circuit. The power supply MIC5219-3.3V have a ENable pin, so if I utilize it, I can get less than 5 micro amps of current draw, which is certainly an overkill, if I use the power on/off thing that cut off 3.3v on the teensy, I can get less than 200 micro amps. I wonder if I can hook a GPIO pin to the power on/off pin, so I can pull it to high or low for a few seconds to turn if off, and also a physical button is connected to the power on/off so I can power it on with one click and hold button to force shutdown.

The linear power supply is [+]Efficient and [+]Small but [-]Can"t output 5v [-]Low max current output [-]Have 500mV dropout voltage @500mA so the battery is unusable when it is 3.7 volts, which is real bad as lithium batteries" protector boards over discharge kicks in @2.4v. I also need 5v for the USB host port for keyboards and mouse. Because the host port is not needed at all times, so I wanted to use existing power bank circuit that auto turns on when peripherals are connected. (Existing circuits are great, maybe efficient and safer), so no boosting required if not needed.

Using the power bank circuit that my li polymer battery comes with (power bank comes with) can [+]output more current, so can also power keyboard mice and hubs. [+]safe, with protection [+]only powers on when there is current draw (Teensy itself may not be able to keep it on, maybe can with the LCD backlight) or/and USB device is connected. Some people add resisters to add current draw, and that is bullshit. Another problem is how to control whether I want the converter to start or not, and have no complete control sucks.

Let us start with the basics first; refresh the knowledge about TN and LCD displays in general, later we will talk about TFTs (Thin Film Transistors), how they differ from regular monochrome LCD displays. Then we will go on to the ghosting effect, so we will not only discuss the technology behind the construction of the TFT, but also some phenomena, like the ghosting effect, or grayscale inversion, that are important to understand when using an LCD TFT display.

Next, we will look at different technologies of the TFT LCD displays like TN, IPS, VA, and of course about transmissive and transflective LCD displays, because TFT displays also can be transmissive and transflective. In the last part we will talk about backlight.

Let us start with a short review of the most basic liquid crystal cell, which is the TN (twisted nematic) display. On the picture above, we can see that the light can be transmit through the cell or blocked by the liquid crystal cell using voltage. If you want to learn more about monochrome LCD displays and the basics of LCD displays, follow this link.

What is a TFT LCD display and how it is different from a monochrome LCD display? TFT is called an active display. Active, means we have one or more transistors in every cell, in every pixel and in every subpixel. TFT stands for Thin Film Transistor, transistors that are very small and very thin and are built into the pixel, so they are not somewhere outside in a controller, but they are in the pixel itself. For example, in a 55-inch TV set, the TFT display contains millions of transistors in the pixels. We do not see them, because they are very small and hidden, if we zoom in, however, we can see them in every corner of each pixel, like on the picture below.

On the picture above we can see subpixels, that are basic RGB (Red, Green, Blue) colors and a black part, with the transistors and electronic circuits. We just need to know that we have pixels, and subpixels, and each subpixel has transistors. This makes the display active, and thus is called  the TFT display. TFT displays are usually color displays, but there are also monochrome TFT displays, that are active, and have transistors, but have no colors. The colors in the TFT LCD display are typically added by color filters on each subpixel. Usually the filters are RGB, but we also have RGBW (Red, Green, Blue, White) LCD displays with added subpixels without the filter (White) to make the display brighter.

Going a little bit deeper, into the TFT cell, there is a part inside well known to us from the monochrome LCD display Riverdi University lecture. We have a cell, liquid crystal, polarizers, an ITO (Indium Tin Oxide) layer for the electrodes, and additionally an electronic circuit. Usually, the electronic circuit consists of one transistor and some capacitors to sustain the pixel state when we switch the pixel OFF and ON. In a TFT LCD display the pixels are much more complicated because apart from building the liquid crystal part, we also need to build an electronic part.

That is why TFT LCD display technologies are very expensive to manufacture. If you are familiar with electronics, you know that the transistor is a kind of switch, and it allows us to switch the pixel ON and OFF. Because it is built into the pixel itself, it can be done very quickly and be very well controlled. We can control the exact state of every pixel not only the ON and OFF states, but also all the states in between. We can switch the light of the cells ON and OFF in several steps. Usually for TFT LCD displays it will be 8-bit steps per color, so we have 256 steps of brightness for every color, and every subpixel. Because we have three subpixels, we have a 24-bit color range, that means over 16 million combinations, we can, at least theoretically, show on our TFT LCD display over 16 million distinct colors using RGB pixels.

Now that we know how the TFT LCD display works, we can now learn some practical things one of which is LCD TFT ghosting. We know how the image is created, but what happens when we have the image on the screen for a prolonged time, and how to prevent it. In LCD displays we have something called LCD ghosting. We do not see it very often, but in some displays this phenomenon still exists.

If some elements of the picture i.e., your company logo is in the same place of the screen for a long period of time, for couple of weeks, months or a year, the crystals will memorize the state and later, when we change the image, we may see some ghosting of those elements. It really depends on many conditions like temperature and even the screen image that we display on the screen for longer periods of time. When you build your application, you can use some techniques to avoid it, like very rapid contrast change and of course to avoid the positioning the same image in the same position for a longer time.

You may have seen this phenomenon already as it is common in every display technology, and even companies like Apple put information on their websites, that users may encounter this phenomenon and how to fix it. It is called image ghosting or image persistence, and even Retina displays are not free of it.

Another issue present in TFT displays, especially TN LCD displays, is grayscale inversion. This is a phenomenon that changes the colors of the screen according to the viewing angle, and it is only one-sided. When buying a TFT LCD display, first we need to check what kind of technology it is. If it is an IPS display, like the Riverdi IPS display line, then we do not need to worry about the grayscale inversion because all the viewing angles will be the same and all of them will be very high, like 80, 85, or 89 degrees. But if you buy a more common or older display technology type, like the TN (twisted nematic) display, you need to think where it will be used, because one viewing angle will be out. It may be sometimes confusing, and you need to be careful as most factories define viewing direction of the screen and mistake this with the greyscale inversion side.

On the picture above, you can see further explanation of the grayscale inversion from Wikipedia. It says that some early panels and also nowadays TN displays, have grayscale inversion not necessary up-down, but it can be any angle, you need to check in the datasheet. The reason technologies like IPS (In-Plane Switching), used in the latest Riverdi displays, or VA, were developed, was to avoid this phenomenon. Also, we do not want to brag, but the Wikipedia definition references our website.

We know already that TN (twisted nematic) displays, suffer from grayscale inversion, which means the display has one viewing side, where the image color suddenly changes. It is tricky, and you need to be careful. On the picture above there is a part of the LCD TFT specification of a TN (twisted nematic) display, that has grayscale inversion, and if we go to this table, we can see the viewing angles. They are defined at 70, 70, 60 and 70 degrees, that is the maximum viewing angle, at which the user can see the image. Normally we may think that 70 degrees is better, so we will choose left and right side to be 70 degrees, and then up and down, and if we do not know the grayscale inversion phenomena, we may put our user on the bottom side which is also 70 degrees. The viewing direction will be then like a 6 o’clock direction, so we call it a 6 o’clock display. But you need to be careful! Looking at the specification, we can see that this display was defined as a 12 o’clock display, so it is best for it to be seen from a 12 o’clock direction. But we can find that the 12 o’clock has a lower viewing angle – 60 degrees. What does it mean? It means that on this side there will be no grayscale inversion. If we go to 40, 50, 60 degrees and even a little bit more, probably we will still see the image properly. Maybe with lower contrast, but the colors will not change. If we go from the bottom, from a 6 o’clock direction where we have the grayscale inversion, after 70 degrees or lower we will see a sudden color change, and of course this is something we want to avoid.

To summarize, when you buy older technology like TN and displays, which are still very popular, and Riverdi is selling them as well, you need to be careful where you put your display. If it is a handheld device, you will see the display from the bottom, but if you put it on a wall, you will see the display from the top, so you need to define it during the design phase, because later it is usually impossible or expensive to change the direction.

We will talk now about the other TFT technologies, that allow us to have wider viewing angles and more vivid colors. The most basic technology for monochrome and TFT LCD displays is twisted nematic (TN). As we already know, this kind of displays have a problem with grayscale inversion. On one side we have a higher retardation and will not get a clear image. That is why we have other technologies like VA (Vertical Alignment), where the liquid crystal is differently organized, and another variation of the TFT technology – IPS which is In-Plane Switching. The VA and IPS LCD displays do not have a problem with the viewing angles, you can see a clear image from all sides.

Nowadays all TV sets, tablets and of course mobile phones are IPS or VA. You can turn them around and see the image clear from all sides. But, for monitor applications the TN technology is still widely used, because the monitor usually is in front of you and most of the time you look directly at it, from top, left or right side, but very rarely from the bottom, so the grayscale inversion viewing angle can be placed there. This technology still is very practical because it is affordable and has some advantages for gamers because it is very fast.

Apart from the different organization of the liquid crystals, we also organize subpixels a little bit differently in a VA and IPS LCD displays. When we look closer at the TN display, we will just see the subpixels with color filters. If we look at the VA or IPS display they will have subpixels of subpixels. The subpixels are divided into smaller parts. In this way we can achieve even wider viewing angles and better colors for the user, but of course, it is more complicated and more expensive to do.

The picture above presents the TN display and grayscale inversion. For IPS or VA technology there is no such effect. The picture will be the same from all the sides we look so these technologies are popular where we need wide viewing angles, and TN is popular where we don’t need that, like in monitors. Other advantages of IPS LCD displays are they give accurate colors, and wide viewing angles. What is also important in practice, in our projects, is that the IPS LCD displays are less susceptible to mechanical force. When we apply mechanical force to the screen, and have an optically bonded touch screen, we push the display as well as squeeze the cells. When we have a TN display, every push on the cell changes the image suddenly, with the IPS LCD displays with in-plane switching, different liquid crystals organization, this effect is lesser. It is not completely removed but it is much less distinct. That is another reason IPS displays are very popular for smartphones, tablets, when we have the touchscreens usually optically bonded.

If we wanted to talk about disadvantages, there is a question mark over it, as some of them may be true, some of them do not rely on real cases, what kind of display, what kind of technology is it. Sometimes the IPS displays can have higher power consumption than others, in many cases however, not. They can be more expensive, but not necessarily. The new IPS panels can cost like TN panels, but IPS panels definitely have a longer response time. Again, it is not a rule, you can make IPS panels that are very fast, faster than TN panels, but if you want the fastest possible display, probably the TN panel will be the fastest. That is why the TN technology is still popular on the gaming market. Of course, you can find a lot of discussions on the internet, which technology is better, but it really depends on what you want to achieve.

Now, let us look at the backlight types. As we see here, on the picture above, we have four distinct types of backlight possible. The most common, 95 or 99 per cent of the TFT LCD displays on the market are the transmissive LCD display type, where we need the backlight from the back. If you remember from our Monochrome LCD Displays lecture, for transmissive LCD displays you need the backlight to be always on. If you switch the backlight off, you will not see anything. The same as for monochrome LCD displays, but less popular for TFT displays, we have the transflective LCD display type. They are not popular because usually for transflective TFT displays, the colors lack in brightness, and the displays are not very practical to use. You can see the screen, but the application is limited. Some transflective LCD displays are used by military, in applications where power consumption is paramount; where you can switch the backlight off and you agree to have lower image quality but still see the image. Power consumption and saving energy is most important in some kind of applications and you can use transflective LCD displays there. The reflective type of LCD displays are almost never used in TFT. There is one technology called Low Power Reflective Displays (LPRD) that is used in TFT but it is not popular. Lastly, we have a variation of reflective displays with frontlight, where we add frontlight to the reflective display and have the image even without external light.

Just a few words about Low Power Reflective Displays (LPRD). This kind of display uses environmental light, ambient light to reflect, and produce some colors. The colors are not perfect, not perfectly clear, but this technology is becoming increasingly popular because it allows to have color displays in battery powered applications. For example, a smartwatch would be a case for that technology, or an electrical bike or scooter, where we can not only have a standard monochrome LCD display but also a TFT LCD color display without the backlight; we can see the image even in

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strong sunlight and not need backlight at all. So, this kind of TFL LCD display technology is getting more and more popular when we have outdoor LCD displays and need a low power consumption.

On the picture above, we have some examples of how transmissive and reflective LCD displays work in the sunlight. If we have a simple image, like a black and white pattern, then on a transmissive LCD display, even with 1000 candela brightness, the image probably will be lower quality than for a reflective LCD display; if we have sunlight, we have very strong light reflections on the surface of the screen. We have talked about contrast in more detail in the lecture Sunlight Readable Displays. So, reflective LCD displays are a better solution for outdoor applications than transmissive LCD displays, where you need a really strong backlight, 1000 candela or more, to be really seen outdoors.

To show you how the backlight of LCD displays is built, we took the picture above. You can see the edge backlight there, where we have LEDs here on the small PCB on the edge, and we have a diffuser that distributes the light to the whole surface of LCD screen.

In addition to the backlight, we have something that is called a frontlight. It is similar to backlight, it also uses the LEDs to put the light into it, but the frontlight needs to be transparent as we have the display behind. On the example on the picture above we can see an e-paper display. The e-paper display is also a TFT display variation, but it is not LCD (liquid crystal), it is a different technology, but the back of the display is the same and it is reflective. The example you see is the Kindle 4 eBook reader. It uses an e-paper display and a frontlight as well, so you can read eBooks even during the night.

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We will organize the kinds of display interfaces we offer, and how they differ. You will get to know what kind of external and internal interfaces we have and what are their main applications.

First, let us start with dividing internal and external interfaces in LCD modules. Internal interface of display means it used inside the device. Those are usually the embedded interfaces that are not visible, and we do not have access to them as the users of the device. External interfaces, on the other hand, are connected to the device using a cable. Once we have defined internal and external interfaces, both of these categories come as universal or image transfer interfaces.

A protocol defines the rules of information exchange, where the interface is the medium. The example here could be the language. When I use my voice to communicate with other people, my voice is an interface. Over this interface my voice is being sent to other people’s ears, and the protocol is the language used. Right now, I am using the English protocol. If you understand the protocol, you understand what I am saying. If I switch to a different language, Polish or some other language that you do not understand, you have the same interface, you will still hear me, but because of a different protocol, you do not understand me anymore. In this article we will talk only about interfaces, how to connect devices to each other. We will not focus on protocols.

Let’s try to get the interfaces right. For internal interfaces, interfaces embedded into the device, we have universal interfaces and image transfer interfaces. Universal display interface can send other data, not only an image. Being universal, they are not perfect for image transfer, because in most of the displays used nowadays, the image transfer is one of the most demanding. The bit rate, the data transfer needed for the image transfer is rather high. Higher that many universal interfaces can offer. If we need to send an image every once in a while, then we don’t need very high bandwidth. If we do not need live video stream, then we can use some of the internal universal interfaces such as SPI, I2C or even slow interfaces as RS232 or UART.

The first universal interface will be SPI (Serial Peripheral Interface). This interface is serial, used for communication between a host, in SPI called a Master, and devices called Slaves. One host can communicate with many slaves. To select the Slave, we use the Chip select or SS line and then we use two data lines, Master output or Master input. And of course we have to define the clock, to synchronize the data, because this is a clock synchronized interface.

It can be fast but is not fast enough for live video. The baud rate can be 1 MBd, but it can also be 10 MBd or even 50 MBd on the SPI or QSPI. QSPI is a Quad SPI, a kind of modification of SPI that is faster. But still this interface is very universal, we can use it to connect memory or some input and outputs internally in our device. In the display universe the SPI is used for simple displays, for small size displays, where we can transfer the image relatively fast, because the resolution is low. The maximum size for SPI display interface would be 3.5 inch, 320 by 240 pixel TFT displays. If we have higher resolution, image transfer will be too slow to use SPI even with a high-speed SPI.

Next, we have the I2C interface. This kind of interface is usually slower than SPI. It uses only two lines, so one is a clock for synchronization, and the other one is the data line. This data line is bidirectional. It means that if in SPI we have two data lines, one outgoing and one incoming, then in an I2C interface we have only one data line.

If, for example, the Master is sending some data, the only thing Slaves can do is to receive it. And then we need to wait a little bit for the Master to finish. We can then respond as Slave to Master. In I2C Slave selection works a little bit different than in SPI, where  we had a Chip Select line (CS line) or SS line to select from. In I2C we first need to send the logical address to the interface that is being written by Slaves. In general, this procedure is slow and universal interface used also to connect the simple memory and some other I2S that we have around our microcontroller on the PCB. It is very useful, but usually not used for image transfer. This interface is very popular in the display world for touchscreens. Most of the embedded touch screens that we use have I2C interface because the touchscreen does not generate many data. We only have coordinates of the finger or few fingers at most, that need to be sent back to the microcontroller, to the device processor. The slow baud rate is good enough for the touchscreen, but not enough for the image.

The UART is basically the same as RS232, but it is a fully internal interface. It is pretty slow. We have a TX line and a RX line – a Transmit Line and a Receive Line. We do not have a clock here, we only have a clock to synchronize the device internally, but the clock signal is not sent out. So, we need to synchronize the data that is coming through the lines and to do that we need to set the same baud rate on both sides of the communication line. That means that before we use UART we need to agree first what speed we will use.

That is not a case for SPI or I2C, because we have a clock there that gives the speed to every device. Then each device works according to the clock. In UART we do not have a clock. It is rather not used for image transfer. The UART, or SPI, or I2C can be used for low resolution displays. For high resolution displays we need an Intelligent Display, a display that will generate the image internally and through these slow universal interfaces we only send commands, or we send the image once, the image is being stored into the internal memory of the intelligent display, that we will use later sending the commands. You can find Riverdi’s intelligent display line on our website: https://riverdi.com/product-category/intelligent-displays/.

These Riverdi products are very advanced Intelligent Displays, made with Bridgetek controllers. The controllers use SPI and QSPI for communication. That means your software, your system, your microcontroller can be simple. You can use SPI interface to drive them, and you can still have high resolution image, even as high as 1280 by 800 pixels in 10.1-inch LCD displays. So, please remember that if you want to use a slow universal interface and have a high-resolution image, you need to use an Intelligent Display.

There are also the internal image transfer interfaces. The image transfer interface allows continuous high speed image transfer. Internal transfer is high enough to refresh the display many times per second. This is called the refresh rate of a display. When you go to a display, monitor, or TV set specification, you will see  refresh rate or maximum refresh rate parameter. If it’s 60 Hertz, that means the display image is refreshed 60 times per second. More advanced displays would have higher values, like 100 Hertz. The refresh rate means we need to send full image 60 times or 100 times in each second. To visualize this amount of data, we need to multiply refresh rate by the resolution of the screen. For example, for a 7-inch Riverdi LVDS display with resolution 1024 by 600 it is roughly 600 thousand pixels.

The most common internal image transfer interface in industrial LCD displays nowadays is LVDS – Low Voltage Differential Signal. A crucial feature of this interface is that it is differential. It means that the signal is immune to interference and we can use a twisted pair of wires to transfer the data. We can send data fast and it will not be corrupt by any noise, interference. This kind of data corruption is quite common in other interfaces.

The next, older image transfer interface is called RGB. Name comes from the colors sent parallelly to the display: red, green and blue. LVDS is a serial interface and the RGB is a parallel interface. The main difference is that RGB is not differential, so it is easier to disturb signal with noise and you configure the speed of this interface too high. Parallel interface means that we send every bit in a separate line. In theory this interface could be fast, but because it is not differential, the transfer speed is limited. Moreover, the RGB display interface will work with rather small screen sizes –  usually up to 7-inch or 10-inch.

12 inch screen size is the total maximum for a LCD display with RGB interface, but the resolution will be lower, like 800 by 600. For this display size it is very low resolution. This is the reason why the 7-inch is size above which the LCD displays are being switched from RGB to LVDS interface. Among Riverdi products (if you go to the Riverdi website and to the IPS display tab), there are displays without the controller, and the small displays like 3.5-inch, 4.3-inch and 5-inch are equipped with RGB interface. But when you go to the 7-inch LCD displays tab on Riverdi website, you will find RGB, LVDS and MIPI displays. But when you go to the 10-inch or bigger displays, you will only find the LVDS displays because our 10-inch LCD displays are high resolution 1280 by 800, and it is impossible to build it with the RGB interface.

MIPI – Mobile Industry Processor Interface – is an internally embedded image transfer interface, getting popular these days. This kind of interface is used in mobile applications, tablets or mobile phones, but it is entering as an option in industrial applications. In Riverdi we offer 7-inch MIPI displays, but please be careful with other MIPI displays on the market. Many come from mobile phones or tablet market. Also, the TFT glass availability may not be stable as the mobile market changes really fast, every six months or every year. When you buy a 7-inch Riverdi MIPI interface display you are safe, because it is an industrial display.

This is why we have a limited number of displays with MIPI interface – we want to be sure that what we sale will be available for a long time. Longevity is one of Riverdi’s core values and we do not want to deliver anything that will not be supported for a minimum 3 to 5 years. It is because many of our customers are making industrial, medical or military devices and they need displays to be available long-term.

Next interface is the Vx1. It is similar to LVDS  and MIPI, so it’s low voltage differential signal. Vx1 is a very high-speed interface, usually used in large high-resolution screens, like 55-inch 4K TVs or even larger ones. If you buy this kind of a TV set right now, probably the embedded interface inside will be the Vx1.

Key takeaway: Vx1 is a super-fast interface used for high bandwidth image transfer, with high refresh rate and high-resolution displays, used in 4K screens and above.

The last internal image transfer interface is Embedded DisplayPort (eDP). We call it the new LVDS, because many new industrial displays are equipped with the eDP. If you go through industrial manufacturers of TFT LCD displays, you will notice increasing number of models available with the eDP. eDP is also a native interface in new Intel or AMD based processors.

Key Takeaway: With the embedded DisplayPort as a native display interface you can cut down costs, because you do not need anything extra to connect a display to the processor.

Now, with the processors on the market, we need displays with embedded DisplayPort. Many laptops or monitors already use embedded DisplayPort as an internal interface instead of LVDS. LVDS still is the most popular industrial LCD display interface. All the internal image transfer interfaces like MIPI, Vx1 and eDP are variations of LVDS, where the protocols and the signals are a little bit different. For example, for eDP we can have lower noise and reduced power consumption. All of them have advantages over regular LVDS, but they are all LVDS type.

Now, let’s take a closer look at external interfaces. Those are the ones that we usually have direct access to. It can be TV or monitor connected to your computer with the HDMI . It can be a DVI usually used for monitors. Or VGA which is an outdated image interface for monitors.  The DisplayPort that is a HDMI successor. Finally, an universal USB-C, the most common interface nowadays used to connect devices.

USB-C transmits up to 100 watt of power, because you can increase voltage and current. In a regular USB it is usually 5 volt and 0.5 or 1.0 amp, so only a couple watts. In USB-C you increase the voltage up to 20 volt and with the 5 amp current, so in total it’s even 100 watt of power.  This interface is made not only for data, but for real power transfer. Through USB-C you can charge your phone and your laptop. If you buy a new laptop right now, you may even not get a regular power connector, but only an USB-C. The USB-C is a very smart interface. If you connect the devices, they can negotiate with each other which one has more power. For example, if we connect a charger to a laptop, the charger has more power and will charge the laptop, but if you connect the laptop with the same interface to your mobile phone, then they will discuss the power levels, and of course the laptop will be charging the phone. You can already find monitors on the market that have USB-C instead of HDMI. Those monitors can be powered from your computer and need only one USB cable, both for image transfer and power.  For sure the future belongs to USB-C implementations.

Let’s move on to image transfer interfaces. The most common one is HDMI – High-Definition Multimedia Interface. M stands for Multimedia, because it transfers image with sound. If you connect your computer to your TV set with HDMI, you will need one cable for both the video and the audio. There are variations of HDMI connectors:

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The next one is DVI – Digital Visual Interface. The first DVI was not a multimedia interface, because it did not have audio data transfer. Nowadays, there are some variations that can transfer audio, but it is non-standard. We can assume DVI is rather for image transfer. It is a digital interface, similar in signals to HDMI. The latest variation is DVI-I, where I stands for integrated interface. It can have a digital and analog part for VGA compatibility. In the picture above there is a DVI-D, digital only, where we do not have the pins for analog VGA interface. Analog VGA is sometimes available in your desktop computer, but not in laptops anymore.

The oldest video interface still in use  is the VGA – Video Graphic Array interface. It becomes less and less popular. This is an analog interface, not a digital one like all the other abovementioned interfaces. Analog interface means that we do not transmit the bits, but we send the voltages values. The analog signals are not stable, they are quite easy to disturb, so the transfer cannot be very high in speed and volume

The last external interface that we can find in our devices nowadays is a DisplayPort. DisplayPort is similar to HDMI or DVI. It can also transfer image and sound. It is even faster than the HDMI. Usually, the DisplayPort is used for high resolution displays, for new monitors and TVs with 4K or 8K resolution where it is really hard, or nearly impossible, to achieve such resolution using HDMI interface.

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In market, LCD means passive matrix LCDs which increase TN (Twisted Nematic), STN (Super Twisted Nematic), or FSTN (Film Compensated STN) LCD Displays. It is a kind of earliest and lowest cost display technology.

LCD screens are still found in the market of low cost watches, calculators, clocks, utility meters etc. because of its advantages of low cost, fast response time (speed), wide temperature range,  low power consumption, sunlight readable with transflective or reflective polarizers etc.  Most of them are monochrome LCD display and belong to passive-matrix LCDs.

TFT LCDs have capacitors and transistors. These are the two elements that play a key part in ensuring that the TFT display monitor functions by using a very small amount of energy without running out of operation.

Normally, we say TFT LCD panels or TFT screens, we mean they are TN (Twisted Nematic) Type TFT displays or TN panels, or TN screen technology. TFT is active-matrix LCDs, it is a kind of LCD technologies.

TFT has wider viewing angles, better contrast ratio than TN displays. TFT display technologies have been widely used for computer monitors, laptops, medical monitors, industrial monitors, ATM, point of sales etc.

Actually, IPS technology is a kind of TFT display with thin film transistors for individual pixels. But IPS displays have superior high contrast, wide viewing angle, color reproduction, image quality etc. IPS screens have been found in high-end applications, like Apple iPhones, iPads, Samsung mobile phones, more expensive LCD monitors etc.

Both TFT LCD displays and IPS LCD displays are active matrix displays, neither of them can produce color, there is a layer of RGB (red, green, blue) color filter in each LCD pixels to make LCD showing colors. If you use a magnifier to see your monitor, you will see RGB color. With switch on/off and different level of brightness RGB, we can get many colors.

Neither of them can’t release color themselves, they have relied on extra light source in order to display. LED backlights are usually be together with them in the display modules as the light sources. Besides, both TFT screens and IPS screens are transmissive, it will need more power or more expensive than passive matrix LCD screens to be seen under sunlight.  IPS screens transmittance is lower than TFT screens, more power is needed for IPS LCD display.

The ATtiny85 is rated at a maximum clock speed of 20MHz at 4.5 – 5.5V. For some applications it would be nice to get the maximum speed without needing to buy a 20MHz crystal, or tie up two I/O lines driving the crystal. Here"s how to do it.

The ATtiny85 is almost unique among the AVR chips in having an internal PLL (Phase-Locked Loop) that can multiply up the internal 8MHz clock by a factor of 8 to 64MHz, for use by Timer/Counter1. By programming a fuse you can choose to use the PLL divided by four as the system clock, giving a clock speed of 16MHz.

Looking at the ATtiny85 datasheet we see that there"s an OSCCAL register that allows you to adjust the internal clock frequency to between almost -50% and +100%:

Thus, by choosing an OSCCAL value of about 192 we can increase the internal clock from 8MHz to 10MHz, and this will give a system clock derived from the PLL of 20MHz.

To test the 20MHz internal clock I set up Timer/Counter1 to toggle the OC1B output (PB4) at the clock frequency, giving a square wave of half the clock frequency:

Compile the program using Spence Konde"s ATTiny Core ATtiny25/45/85 option under the ATtinyCore heading on the Board menu. Then choose Timer 1 Clock: CPU, B.O.D. Disabled, ATtiny85, 16 MHz (PLL) from the subsequent menus. Choose Burn Bootloader to set the fuses appropriately. Then upload the program using ISP (in-system programming); I used Sparkfun"s Tiny AVR Programmer Board; see ATtiny-Based Beginner"s Kit.

With the correct OSCCAL value that gives a 20MHz system clock this should produce an output of 10MHz on PB4. I found the value 181 gave the closest value.

The datasheet states that "the fast peripheral clock will saturate ... at about 85MHz". This means that we can expect to achieve a maximum system clock speed of 85/4 or 21.25MHz by adjusting OSCCAL. In practice I found I could go higher than this.

Two other AVR chips include a PLL: the ATtiny861, and the ATmega32u4, and it should be possible to use the same technique with these chips to provide a 20MHz internal clock.

The content is intended to be updated from time to time, I will add more details if I found new display or library update. You can also help me enrich the content by leaving comments below.

You can run various IoT projects prefectly without any display. But not all IoT project only feed data in single direction (IoT to server), some IoT also gather real time information from the server for displaying.

My previous instructables, ESP32 Photo Clock is am example, it download a current minute photo from the Internet, decode the JPEG photo and display it.

There are various real time information in your server or Internet, such as all rooms temperature in your home, server CPU usage, weather forecast, news, stock price, your downloading file is done, your Youtube channel views :>

Many Arduino projects use monochrome display, one of the reason is the limited resources of a MCU. 320 pixels width, 240 pixels height and 8 bits color for each RGB color channel means 230 KB for each full screen picture. But normal Arduino (ATmega328) only have 32 KB flash and it is time consuming (over a second) to read data from SD card and draw it to the color display.

ESP32 have changed the game! It have much faster processing power (16 MHz vs 240 MHz dual core), much more RAM (2 KB vs over 200 KB) and much more flash (32 KB vs 4 MB), so it is capable to utilize more color and higher resolution image for displaying. At the same time it is capable to do some RAM hungry process such as Animated GIF, JPEG or PNG file decoding, it is a very important feature for displaying information gathered from the internet.

Color display have many type of interfaces: Serial Peripheral Interface (SPI), 6-bit, 8-bit, 16-bit, 18-bit and 24-bit parallel interfaces and also NeoPixel!

SPI dominate the hobby electronics market, most likely because of fewer wire required to connect. Most display in my drawer only have SPI pins breaking out, so this instructables focus on SPI display and a few 8-bit display.

NeoPixel matrix is a very special type of color display. If you are interested in NeoPixel matrix display, here are some of my instructables using it:

There are various color display for hobby electronics: LCD, IPS LCD, OLED with different resolutions and different driver chips. LCD can have higher image density but OLED have better viewable angle, IPS LCD can have both. OLED have more power efficient for each light up pixel but may have burn-in problems. Color OLED operate in 14 V, it means you need a dedicate step-up circuit, but it is not a problem if you simply use with a break-out board. LCD in most case can direct operate in 3.3 V, the same operating voltage as ESP32, so you can consider not use break out board to make a slimmer product.

Software support on the other side also influence your selection. You can develop ESP32 program with Arduino IDE or direct use ESP-IDF. But since ESP-IDF did not have too much display library and not much display hardware supported, so I will concentrate on Arduino display libraries only.

For the beginner, I think buying adafruit, or similar supportive vendor, hardware and using its Arduino library can have good seamless experience (though I have no budget to try it all). TFT_eSPI library have better performance but configuration require make changes in the library folder. Ucglib and UTFT-ESP run a little bit slow but it support many hardware and it is a popular library, you can find many Arduino projects using it. LovyanGFX library start appear at 2019, it support many dev device such as M5Stack, M5StickC, TTGO T-Watch, ODROID-GO, ESP-WROVER-KIT, WioTerminal and more. I am also writing a new library called Arduino_GFX since 2019.

OLED have a big advantage, the pixel only draw power if it lights up. On the other hand, LCD back light always draw full power even you are displaying a black screen. So OLED can help save some power for the project powered by a battery.

This is a 1.5" 128 x 128 color OLED, this form factor is very fit for smart-watch-like wearable project. The most barrier of select this should be the price tag is around 4 times of a normal LCD.

ST7735 is a very popular LCD driver model for the resolution 128x128 and 128x160. It may cause by its popularity, there are many manufacturer produce compatible product. However, they are not fully compatible.

Thanks for the popularity of wearable gadget, I can find more small size IPS LCD in the market this year(2018). The above picture is an 0.96" 80x160 IPS color LCD using ST7735 driver chip. As you can see in the 3rd picture, you can treat it as a 128x160 color display in code but only the middle part is actually displaying. The 4th picture is the display without breakout board, it is thin, tiny and very fit for a wearable project!

SSD1283A is 1.6" 130x130 display, it claim only consume 0.1 in sleep mode and backlight turned off. In sleep mode the last drawn screen still readable under sufficient lighting.

It is a 2.2" 176x220 color LCD. It is relatively fewer projects using this chips and resolution. It may caused by the success of its chip family brother, ILI9341 (0.2" larger in size but have near double resolution).

I think ILI9341 is the most popular LCD driver chip in the hobby electronics market. In most case it is 240x320 resolution and have many screen size from 1.7" to 3.5". Some breakout board also built-in touch screen feature.

This also the highest pixel density color display in my drawer. As same as normal LCD, it can direct operate in 3.3 V, so it is very good for making slim wearable device.

There are many display libraries that can support various hardware. I have picked 4 of most popular Arduino library for comparison:Adafruit GFX Family

The display speed is one of the most important thing we consider to select which library. I have chosen TFT_eSPI PDQ test for this comparison. I have made some effort to rewrite the PDQ test that can run in 4 libraries. All test will run with the same 2.8" ILI9341 LCD.

As I found TFT_eSPI is the most potential display library for ESP32 in this instructables, I have paid some effort to add support for all my display in hand. The newly added display support marked letter M in red at the above picture, here is my enhanced version:

Adafruit sell various display module in hobby electronics market and they also have very good support in software level. Their display libraries all built on a parent class called Adafruit_GFX, so I call it Adafruit GFX Family. This library generally support most Arduino hardware (also ESP32).

In Arduino Library Manager simply search "adafruit display", you can see all the family members. If you want to install it, say ILI9341, simply select "Adafruit ILI9341" and then click install. Remember also install its dependent library "Adafruit GFX Library".

This library method signature is very similar to Adafruit GFX, but it is tailor-made for ESP8266 or ESP32. I think the source code is optimised for ESP32, so the PDQ result is much faster than other libraries.

Note: The most difficult part using this library is you are required to configure this library before you can use it. The configuration file is located at the library folder, it should be "Arduino/libraries/TFT_eSPI/User_setup.h" under you own documents folder. It have many comments help you to do that, please follow the comments step by step to finish the configuration. Here is my User_setup.h for ILI9341:

#define LOAD_GLCD // Font 1. Original Adafruit 8 pixel font needs ~1820 bytes in FLASH
#define LOAD_FONT2 // Font 2. Small 16 pixel high font, needs ~3534 bytes in FLASH, 96 characters

ESP32 + ILI9341 can run at SPI speed 40 MHz, it require some code change at library folder. The above pictures are the fine tuned result. Here are the code change summary:

ST7735 and ILI9341 are the most popular display, this 2 are better option for the beginner. You may notice LCD have a big weakness, the viewable angle, some color lost outside the viewable angle and the screen become unreadable. If you have enough budget, OLED or IPS LCD have much better viewable angle.

In most case, we study how to use a code library by searching sample on the web. I have tried search four libraries keyword in Github, Adafruit is most popular and UTFT the second.

ILI9341 should be most valuable display for the beginner. Adafruit GFX Library should be most easy to use for the beginner, and since TFT_eSPI have very similar method signature, it is very easy to switch to a faster library later on.

OLED require 14 V to light up the pixel so it is not easy to decouple the breakout board. On the other hand, LCD (also IPS LCD) usually operate in 3.3 V, as same as the ESP32. In most case, there are only the LED control circuit required between LCD and ESP32, i.e. a transistor and few resistors. So it relatively easy to make it.

It is very important to read the data sheet first before you decide not using breakout board. The pins layout, pin pitch size, the sample circuit connection and maximum rating all you can find in data sheet. The maximum voltage is especially important, you should sticky follow the rating or you will blow your LCD. The chip can operate in 3.3 V but LED may be 2.8 - 3.0 V so it require some electronics in the middle, most data sheet have the sample circuit. You may ask your seller send a soft copy of data sheet to you or simply Google it by the model number.

My special hint: I like to soldering a FPC cable with the same pin pitch size as the LCD to help the connection with the MCU. I have used this technique in these instructables:

If you read through the data sheet of the color display, you may find most of color display can support 18 bit color depth (6 bit for each RGB channel). 18 bit color depth can have a better image quality that 16 bit color depth (5 bit in red and blue channel, 6 bit for green channel). However, only Ucglib actually run at 18 bit color depth (262,144 colors), other 3 libraries all run at 16 bit color depth (65,536 colors). It is because 18 bit color depth actually require transfer 3 bytes (24 bit) of data for each pixel, it means 50% more data require to transfer and store in memory. It is one of the reason why Ucglib run slower, but it can have a better image quality.

Thank you very much for posting this detailed review of the color display option available for "Duino users. You have saved me hours, maybe days of time wandering the web looking for information.0

Great article! Very interested in round displays. There are available round displays based on st7687s (128 * 128) and st7789 (240 * 240), but I have not found any information on practical use.

Hello! Yes, I purchased this display from keyestudio, connected it to esp32 using this library from dfrobot. It is only necessary to consider that the pinout of the display connectors differs from dfrobot and keyestudio.

I"m wanting to connect a VGA camera, the sort you find as a little module on eBay with OVPxxxx chip, to a screen such as ILxxxx family, which appears to have direct VGA input. I think it will work if I connect the camera directly with no MCU, but I"d also like to add a cross-hair to the display (for a drill targetting system). I wonder is it possible to intercept the serial video data and change individual pixels in a streaming fashion, instead of loading a whole screen into memory, changing it and passing it on? I ask because it seems to me it would need a much less powerful MCU.0

Thank you so much for such a great article. I have been trying to choose the best library to use for a project that will use either a SSD1351 or a ST7735 both being 128x128. The key to my project is to be able to dump a frame buffer in to the display and then recalculate the next frame buffer. :)

CS stands for cable select, it tell the device the SPI is active for that device. If you only have 1 device connected to the the SPI, you can simply pull down the CS pin to tell it always active. It can also simplify the code no need turn CS on and off for each message and run a little bit faster. Some breakout board not wire out CS pin and simply pull it down for you.0

So, basically I make a reset in the beggining (read datasheet) then next I use only SPI_DAT and SPLI_CLK. If I destroy the sequence touching with an oscilloscope, the LCD stops to understand the sequence DAT/CLK and I have to make another reset.

Those 2 pins must be dedicated to the display, otherwise the display will get confused without the CS pin. One DAT/CLK to LCD and another DAT/CLK to I2C.

Hello! Thank"s for your instruction. I want to use your 8pin ili9486 320x480 spi display with one of your presented libraries and esp32. 1.) Could you please tell me the connections between the display and the esp32 and 2.) which numbers do I have to write into the line utft myglcd (ili9486,?,?,?,?)?

Before you get a new monition for your organization, comparing the TFT display vs IPS display is something that you should do. You would want to buy the monitor which is the most advanced in technology. Therefore, understanding which technology is good for your organization is a must. click to view the 7 Best Types Of Display Screens Technology.

Technology is changing and becoming advanced day by day. Therefore, when you are looking to get a new monitor for your organization, LCD advantages, and disadvantage,  you have to be aware of the pros and cons of that monitor. Moreover, you need to understand the type of monitor you are looking to buy.

That is why it is important to break it down and discuss point by point so that you can understand it in a layman’s language devoid of any technical jargon. Therefore, in this very article, let’s discuss what exactly TFT LCDs and IPS LCDs are, and what are their differences? You will also find out about their pros and cons for your organization.

The word TFT means Thin-Film-Translator. It is the technology that is used in LCD or Liquid Crystal Display. Here you should know that this type of LCD is also categorically referred to as active-matrix LCDs. It tells that these LCDs can hold back some pixels while using other pixels. So, the LCD will be using a very minimum amount of energy to function. TFT LCDs have capacitors and transistors. These are the two elements that play a key part in ensuring that the display monitor functions by using a very small amount of energy without running out of operation.

Now, it is time to take a look at its features that are tailored to improve the experience of the monitor users significantly. Here are some of the features of the TFT monitor;

The display range covers the application range of all displays from 1 inch to 40 inches as well as the large projection plane and is a full-size display terminal.

Display quality from the simplest monochrome character graphics to high resolution, high color fidelity, high brightness, high contrast, the high response speed of a variety of specifications of the video display models.

No radiation, no scintillation, no harm to the user’s health. In particular, the emergence of TFT LCD electronic books and periodicals will bring humans into the era of a paperless office and paperless printing, triggering a revolution in the civilized way of human learning, dissemination, and recording.

It can be normally used in the temperature range from -20℃ to +50℃, and the temperature-hardened TFT LCD can operate at low temperatures up to -80 ℃. It can not only be used as a mobile terminal display, or desktop terminal display but also can be used as a large screen projection TV, which is a full-size video display terminal with excellent performance.

The manufacturing technology has a high degree of automation and good characteristics of large-scale industrial production. TFT LCD industry technology is mature, a mass production rate of more than 90%.

It is a perfect combination of large-scale semiconductor integrated circuit technology and light source technology and has great potential for further development.

TFT LCD screen from the beginning of the use of flat glass plate, its display effect is flat right angles, let a person have a refreshing feeling. And LCDs are easier to achieve high resolution on small screens.

The word IPS refers to In-Plane-Switching which is a technology used to improve the viewing experience of the usual TFT displays. You can say that the IPS display is a more advanced version of the traditional TFT LCD module. However, the features of IPS displays are much more advanced and their applications are very much widespread. You should also know that the basic structure of the IPS LCD is the same as TFT LCD if you compare TFT LCD vs IPS.

As you already know, TFT displays do have a very quick response time which is a plus point for it. But, that does not mean IPS displays a lack of response time. In fact, the response time of an IPS LCD is much more consistent, stable, and quick than the TFT display that everyone used to use in the past. However, you will not be able to gauge the difference apparently by watching TFT and IPS displays separately. But, once you watch the screen side-by-side, the difference will become quite clear to you.

The main drawback of the TFT displays as figured above is the narrow-angle viewing experience. The monitor you buy for your organization should give you an experience of wide-angle viewing. It is very much true if you have to use the screen by staying in motion.

So, as IPS displays are an improved version of TFT displays the viewing angle of IPS LCDs is very much wide. It is a plus point in favor of IPS LCDs when you compare TFT vs IPS. With a TFT screen, you cannot watch an image from various angles without encountering halo effects, blurriness, or grayscale that will cause problems for your viewing.

It is one of the major and remarkable differences between IPS and TFT displays. So, if you don’t want to comprise on the viewing angles and want to have the best experience of viewing the screen from wide angles, the IPS display is what you want. The main reason for such a versatile and wonderful viewing angle of IPS display is the screen configuration which is widely set.

Now, when you want to achieve wide-angle viewing with your display screen, you need to make sure it has a faster level of frequency transmittance. It is where IPS displays overtake TFT displays easily in the comparison because the IPS displays have a much faster and speedier transmittance of frequencies than the TFT displays.

Now the transmittance difference between TFT displays and IPS displays would be around 1ms vs. 25ms. Now, you might think that the difference in milliseconds should not create much of a difference as far as the viewing experience is concerned. Yes, this difference cannot be gauged with a naked eye and you will find it difficult to decipher the difference.

However, when you view and an IPS display from a side-by-side angle and a TFT display from a similar angle, the difference will be quite evident in front of you. That is why those who want to avoid