1 wire lcd display brands

I needed an LCD-display for a project, but only 1 pin was available for driving it. No problem; there are examples from Elektor and others for such an interface. Most of these use a shift register, which was not available in my private store. Therefore the same function will be realised in software using a small microcontroller.

I used a 14-pin PIC microcontroller 16F1825, but the cheaper 16F1823 will also work. Most pins are needed for the display, but still 1 pin is available for a new function (or 2 if low voltage programming is disabled). Two serial inputs are available for the interface: an rs232 compatible one, which for instance can be connected to a PC (I used this one to test the firmware) and a direct connection to the PIC, which can be used to connect the circuit to another microcontroller. In the latter case Q2 and surrounding components can be omitted.

The first idea was to realise the display as a small VT52 or VT100 terminal, but this was too much effort for such a simple device. The final version therefore does not contain much intelligence.

Initially the program simply sends the 4 LSB"s of any received character to the LCD, using bit 4 to control the RS-input. Using ASCII-characters 0x20 to 0x3f (" " to "?", see examples) the display can be fully controlled.

Later I added the possibility to switch on and off the backlight and to send 8 bit control and data. Sending a string for instance now can simply be done by putting the LCD in 8 bit data mode by sending a code followed by the string as ASCII-characters. Sending an Escape-character returns to 4 bit mode. Using 8 bit control is less usefull, because in many cases not more efficient than 4 bit control.

A second addition was a time-out on the reception of the second nibble in 4 bit mode. If it is not received within 1 second, the controller forgets the first nibble. The time-out can be made smaller by changing parameter MAXTIM and by another prescaler factor for timer 0. The time of 1 second was needed

Because the lack of intelligence, all kind of displays based on HD44780 and compatibles can be used. Information about number of lines and characters are kept on the sending side.

This can be "cheated" to just use one pin and timed-length pulse. An RC network is used to provide a time delay for the DAT line to change. Very short pulses mean that a 1 bit is shifted in. With a long enough pulse the DAT voltage drops low enough so that a 0 bit is shifted in when the CLK line goes / again.

Currently I have a 2 wire system with a SN164 that works well so I am not in a hurry to do an LCD on 1 pin, but I may give it a try for use with an attiny850

The LCD is not what is special. The special part is the black elastomeric connector. They are sometimes used with LCDs, since most of the connections are very low current, a high-quality connection is not necessary.

Display size, contrast, color, brightness, resolution, and power are key factors in choosing the right display technology for your application. However, making the right choice in how you feed the information to the display is just as vital, and there are many interface options available.

All displays work in a similar manner. In a very basic explanation, they all have many rows and columns of pixels driven by a controller that communicates with each pixel to emit the brightness and color needed to make up the transmitted image. In some devices, the pixels are diodes that light up when current flows (PMOLEDs and AMOLEDs), and in other electronics, the pixel acts as a shutter to let some of the light from a backlight visible. In all cases, a memory array stores the image information that travels to the display through an interface.

According to Wikipedia, "an interface is a shared boundary across which two separate components of a computer system exchange information. The exchange can be between software, computer hardware, peripheral devices, humans, and combinations of these. Some computer hardware devices such as a touchscreen can both send and receive data through the interface, while others such as a mouse or microphone may only provide an interface to send data to a given system.” In other words, an interface is something that facilitates communication between two objects. Although display interfaces serve a similar purpose, how that communication occurs varies widely.

Serial Peripheral Interface (SPI) is a synchronous serial communication interface best-suited for short distances. It was developed by Motorola for components to share data such as flash memory, sensors, Real-Time Clocks, analog-to-digital converters, and more. Because there is no protocol overhead, the transmission runs at relatively high speeds. SPI runs on one master (the side that generates the clock) with one or more slaves, usually the devices outside the central processor. One drawback of SPI is the number of pins required between devices. Each slave added to the master/slave system needs an additional chip select I/O pin on the master. SPI is a great option for small, low-resolution displays including PMOLEDs and smaller LCDs.

Philips Semiconductors invented I2C (Inter-integrated Circuit) or I-squared-C in 1982. It utilizes a multi-master, multi-slave, single-ended, serial computer bus system. Engineers developed I2C for simple peripherals on PCs, like keyboards and mice to then later apply it to displays. Like SPI, it only works for short distances within a device and uses an asynchronous serial port. What sets I2C apart from SPI is that it can support up to 1008 slaves and only requires two wires, serial clock (SCL), and serial data (SDA). Like SPI, I2C also works well with PMOLEDs and smaller LCDs. Many display systems transfer the touch sensor data through I2C.

RGB is used to interface with large color displays. It sends 8 bits of data for each of the three colors, Red Green, and Blue every clock cycle. Since there are 24 bits of data transmitted every clock cycle, at clock rates up to 50 MHz, this interface can drive much larger displays at video frame rates of 60Hz and up.

Low-Voltage Differential Signaling (LVDS) was developed in 1994 and is a popular choice for large LCDs and peripherals in need of high bandwidth, like high-definition graphics and fast frame rates. It is a great solution because of its high speed of data transmission while using low voltage. Two wires carry the signal,  with one wire carrying the exact inverse of its companion. The electric field generated by one wire is neatly concealed by the other, creating much less interference to nearby wireless systems. At the receiver end, a circuit reads the difference (hence the "differential" in the name) in voltage between the wires. As a result, this scheme doesn’t generate noise or gets its signals scrambled by external noise. The interface consists of four, six, or eight pairs of wires, plus a pair carrying the clock and some ground wires. 24-bit color information at the transmitter end is converted to serial information, transmitted quickly over these pairs of cables, then converted back to 24-bit parallel in the receiver, resulting in an interface that is very fast to handle large displays and is very immune to interference.

Mobile Industry Processor Interface (MIPI) is a newer technology that is managed by the MIPI Alliance and has become a popular choice among wearable and mobile developers. MIPI uses similar differential signaling to LVDS by using a clock pair and one to eight pairs of data called lanes. MIPI supports a complex protocol that allows high speed and low power modes, as well as the ability to read data back from the display at lower rates. There are several versions of MIPI for different applications, MIPI DSI being the one for displays.

Display components stretch the limitations of bandwidth. For perspective, the most common internet bandwidth in a residential home runs on average at around 20 megabits per second or 20 billion 1s and 0s per second. Even small displays can require 4MB per second, which is a lot of data in what is often a tightly constrained physical space.

To give an example, a small monochrome PMOLED with a resolution of 128 x 128 contains 16,384 individual diodes. A still image of various diodes carrying current represents a frame. A frame rate is the number of times that a picture needs refreshing. Most videos have a frame rate of 60 fps (frames per second), which means that it is updated 60 times every second.

Take the same PMOLED display with the 128 x 128 resolution and 16,384 separate diodes; it requires information as to when and how brightly to illuminate each pixel. For a display with only 16 shades, it takes 4 bits of data. 128 x 128 x 4 = 65,536 bits for one frame. Now multiply it by the 60Hz, and you get a bandwidth of 4 megabits/second for a small monochrome display.

The Serial LCD Kit includes all the parts you need to add a serial "backpack" to a 16x2 LCD. The kit includes a pre-programmed ATmega328 microprocessor, which reads a serial stream of data and (after a little heavy-lifting) instantly displays it on the LCD. Interfacing the Serial LCD with an Arduino, or other serial-enabled devices, allows you to easily print GPS coordinates, short messages or any other information onto the LCD.

This tutorial will cover everything you need to know to get up and running with the Serial Enabled LCD Kit. We"ll first go over assembly so you can turn that bag-o-parts into something that hopefully resembles any pictures you may have seen of the kit.

Following assembly, we"ll touch on how to actually use the Serial LCD Kit. Specifically, we"ll go over how you"d use the thing with everybody"s favorite development board, Arduino. There"ll be example code galore, and you can even make your own LCD clock! It"s gonna be pretty crazy...

Finally, you"ll need something to send a serial stream of data to the display. An Arduino works great (any variety, this isn"t limited to the Uno) if you want to automate the serial data stream. FTDI breakouts or RS-232 level shifters work if you just want to connect the display to your computer and send data via a terminal program. For what it"s worth, this tutorial will focus on connecting the display to an Arduino.

The goal of the Serial LCD Kit is to make controlling an LCD simple and to make wiring to it even simpler. If you wanted, you could abstain from using the serial backpack and wire an Arduino directly up to the LCD. To that point, there are loads of great examples, and even some Arduino libraries, that make interfacing a microcontroller directly to an LCD very easy. However, because the LCD is driven by a parallel interface, those examples require a tangle of wires and anywhere from 6 to 11 pins of the Arduino to control the thing.

The microcontroller on the Serial LCD Kit takes care of all of that nasty wiring, so you only need one pin to control the LCD. The Serial LCD"s on-board microcontroller parses any incoming commands or characters, and then sends the proper data to the LCD over the multi-wire parallel interface. It"s a magic black box, and you don"t have to care how it does its job, just that it does it. So let"s get it built...

What you"ve got in front of you right now is not yet a Serial LCD Kit. First, we"ve got to turn that bag of parts into a Serial LCD Kit, which will require soldering. If you"ve never soldered before, don"t fret! This is one of the easier soldering projects, every part is through-hole, and well-spaced. If this is your first time though, I"d encourage you to take a trip over to one of our excellent soldering tutorials before picking up the iron.

First, pick out the big, ferrari-red PCB. See how one side has white silkscreen printed onto it? This is the top of the PCB. You"ll stick almost every part in on this side and solder the pins to the opposite side. The only time we"ll stray from that is when soldering the LCD, which is the last step.

We"ll solder the lowest-profile parts first, so single out that little 10kΩ resistor. Bend it into a "U" shape and guide the two legs through their mating holes. Now just flip the board over and solder both legs to the bottom of the PCB. If the resistor keeps falling out before you can get it good and soldered, bend the legs out a little bit to better secure it. Try to keep the part as flush as possible with the PCB. After soldering, make sure you clip the excess of the legs as close to the solder joint as possible.

Next, find all four of the yellow ceramic capacitors, and separate them by their 3-digit code. “104” means 0.1uF, while “220” signifies 22pF. Don"t mix these up. Stick the caps into their corresponding, rectangular footprint, flip over the board and solder up both legs. Clip the excess legs. Follow the same process for the white, three-pin JST connector, and the silver, oval crystal.

Pick out the 10uF electrolytic capacitor. It"s a little black, can-looking part. Before plugging it into the board, notice that one of the legs is shorter than the other. Whenever you see this asymmetry, consider it an alert that the part is polarized, which means, in order for the part to work correctly, you have to assemble it in a very specific direction. In this case, the shorter leg signifies the negative pin of the capacitor. If you look closely at this capacitor"s landing spot on the PCB, you"ll notice an inviting white dash which marks the negative pin. Match up the negatives and follow the same soldering/clipping process as usual.

Wait...something"s missing...oh, hi LCD! To connect the LCD to the PCB, we"ve included a straight 16-pin header with the kit. You"ll need to solder this header to both the PCB and the LCD. Solder it first to the LCD, stick the shorter pins into the LCD. Make sure the longer legs are extended out from the back of the LCD and solder all 16-pins on the top side of the LCD. Effort to keep the pins as perpendicular to the LCD as possible.

With the header soldered to the LCD,you"ll finally be able to connect the display to the PCB. Remember, we"re sticking this part into the bottom side of the PCB, and soldering to the top. Solder up all 16 pins, and that should be it.

Before you can display anything on the LCD, you"ll have to connect something to it. Only three wires are necessary to use the Serial LCD Kit: RX, GND and VCC. Plug the included 3-wire jumper cable into its mating JST connector that you soldered onto the PCB. This color coded cable has two wires for power, and one for receiving serial data. The red and black wires correspond to +5V and GND, respectively, and the yellow wire is RX.

You"ll need to figure out how you"re going to powerthe LCD Kit. It doesn"t have a regulator on-board, so it"s up to you to supply a clean, regulated 5V power source. If you"re using an Arduino, you could power the Kit off of the 5V and GND pins – connect red to 5V and black to GND. Otherwise, there"s a ton of options out there for power; you could use a USB adapter, a 5V wall-wart, a breadboard power supply. The list just goes on. Just make sure you"re not supplying any more than 5V (a little less may work, but you"ll lose some brightness).

After powering the Serial LCD Kit, you should notice the backlight turn on. If the contrast is properly adjusted, you might see the splash screen flash for a second or two. Most likely though, the contrast won"t be set correctly, so you won"t see a splash screen. In that case, you may see anything from 32 white boxes to absolutely nothing. You"ll have to be quick about it, because the splash screen only remains for a couple seconds before going blank, but try turning the trimpot knob until you"ve got a good view of the characters on the LCD.

The "Serial" in the Serial LCD Kit can be a little confusing. What it really means is TTL serial, not to be confused with RS-232 serial. The voltage on the RX line should only go between 0 and +5V. If you"re using a microcontroller (like an Arduino) to talk with the LCD, then you most likely don"t have to worry. Just don"t hook up a PC"s serial port straight to the LCD and expect it to survive.

Connect the Arduino to the Serial LCD as follows. If you have a wire stripper, you may want to expose a few millimeters more of wire to allow them to stick really nicely into the Arduino"s headers.

Here"s a simple example sketch, which uses the SoftwareSerial library (which is included with recent versions of Arduino) to instill our Arduino with more than just the one, hardware, serial port. Now we can use the hardware serial port to listen to the serial monitor, and the second serial port can be used to talk to the LCD.

Now, plug in your Arduino and upload the code. Open up the serial monitor, and make sure it"s set to 9600. Type “Hello, world” into the serial monitor and send it over to the Arduino. The LCD should echo your greeting. Take the LCD for a test drive, discover all the characters it can display!

You"ll quickly notice, that the code is severely lacking any sort of clear display command, but don"t think for a second that the Serial LCD Kit doesn"t have a clear display command. It"s got commands up the wazoo! The Serial LCD Kit is set up to accept commands that control the backlight, baud rate, and all sorts of display functionality, like clearing the screen. Have a look at the Kit"s “datasheet”, which lists all of the characters and commands you can send to the display. I wrote that, but I understand if it"s all gobbledygook to you right now.

The commands are divided into three groups: backlight, baud rate, and special commands. Each command requires that you send at least two bytes to the display. For instance to set the backlight, you first have to send the backlight control byte (0x80, or decimal 128) followed by a byte with any value from 0 to 255. Sending a 0 will turn the backlight completely off, 255 will turn it all the way on, 127 will set it to about 50%, and so on. The backlight setting is stored in the Serial LCD Kit"s memory and will be restored when the LCD is turned off and on.

What we really care about right now, though, is clearing the display, which requires a special command. To issue a special command to the LCD, you first have to send 0xFE (or decimal 254) which tells the display to go into special command mode, and wait for a data byte. The clear display command is 0x01 (or decimal 1), that command should be sent immediately after sending the special command byte. So to clear the display we need to send two bytes: 254 (0xFE) followed by 1 (0x01). Check out the datasheet link for all of the special commands. You can do all sorts of fun stuff: scroll the display, turn it on/off and control the cursor.

Our next piece of example code, Serial_LCD_Kit_Clock, delves into sending special commands to the LCD with an Arduino. There are individual functions that clear the display (clearDisplay()), set the backlight (setBacklight(byte brightness)), and set the cursor (setLCDCursor(byte cursor_position)), feel free to copy these and add them to any code you"d like.

This is a good start, but there"s plenty of room for growth. Try adjusting the brightness of the display based on what time it was. Make it the brightest at midnight, dimmest at noon. What else can you do with the code?

Now then, that should be enough to get you on your way to using the Serial LCD Kit with a serial interface. If you"re happy with that, and don"t want your mind blown, I suggest you stop reading here.

Oh, you"ve taken the red pill? Well then you get to learn the Serial LCD Kit"s very deep, dark secret. It may not look anything like one, but the LCD Kit is actually Arduino-compatible. It has an ATmega328, just like the Arduino, and that ATmega328 has a serial bootloader, just like an Arduino. It can be programmed via a USB-to-Serial board. This means you can hook up all sorts of sensors, blinkies and other I/O to the Kit itself, while continuing to use the LCD to display any info you"d like. The 6-pin serial programming port on the right hand side of the PCB can be connected to an FTDI Basic Breakout.

With the FTDI board connected, and Arduino open, simply select the corresponding COM port in the Tools>Serial Port menu, and select Arduino Duemilanove or Nano w/ ATmega328 under the Tools>Boards menu. Though it probably won"t look like it"s doing anything, try uploading Blink, change the LED pin to 9 to at least see the backlight of the LCD flick on and off. Remember, you can download the Serial LCD Kit firmware here. If you ever want to turn it back into a Serial LCD, upload it to the LCD like you would any sketch.

If you want to be really adventurous, and get the most out of the Serial LCD Kit, I"d recommend first taking a trip over to where the Serial LCD Kit"s source code is hosted and getting a good idea how the code works. That firmware is written as an Arduino sketch, and uses a great little Arduino library named LiquidCrystal to control the LCD. The LiquidCrystal library makes controlling the LCD with an Arduino super-simple.

You should also get a good feeling for the kit"s schematic. There are a few Arduino pins that can only be used with the LCD (4-9), but pins 10-13, and all of the analog pins can be used with any device you"d normally connect to an Arduino. The available pins are all broken out on the bottom of the PCB.

Remember, this part is all very extracurricular. Don"t feel at all required to use your Serial LCD Kit as an Arduino. I just wanted to let you know what"s possible with this kit.

Serial LCD Clock Example Sketch - Displays a digital clock on the Serial LCD. This is a good example of how to use special commands, like clear, with the display.

Now I"ll leave you and your Serial LCD Kit in peace. I hope you"ve learned a good amount about the display. I also hope you"re left with questions and ideas about what you"re going to do with it next. If you"ve still got questions about the display, or comments about the tutorial, please drop them in the comments box below or email us.

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An LCD monitor is a flat screen using liquid crystal technology to create the display. It is used in place of CRT (cathode ray tube) monitors to display all types of verbal or graphic information.

These monitors are used wherever displays are necessary, including numerical control screens for machine tools, human-machine interfaces (HMI) or simply as industrial computer screens.

LCD monitors are among those that control the transmission or reflection of a separate light source rather than generating their own. The various technologies include twisted nematic (TN), super twisted nematic (STN), film compensated super twisted nematic (FSTN) and thin film transistor (TFT).