lcd displays that are compatible with the hitachi hd44780 driver brands

I cannot post a link in the first message, so please check the reply I"ll write for this very message, and I"ll post a link to the shop I"d like to use...

The Hitachi HD44780 LCD controller is an alphanumeric dot matrix liquid crystal display (LCD) controller developed by Hitachi in the 1980s. The character set of the controller includes ASCII characters, Japanese Kana characters, and some symbols in two 40 character lines. Using an extension driver, the device can display up to 80 characters.

The Hitachi HD44780 LCD controller is limited to monochrome text displays and is often used in copiers, fax machines, laser printers, industrial test equipment, and networking equipment, such as routers and storage devices.

Compatible LCD screens are manufactured in several standard configurations. Common sizes are one row of eight characters (8×1), and 16×2, 20×2 and 20×4 formats. Larger custom sizes are made with 32, 40 and 80 characters and with 1, 2, 4 or 8 lines. The most commonly manufactured larger configuration is 40×4 characters, which requires two individually addressable HD44780 controllers with expansion chips as a single HD44780 chip can only address up to 80 characters.

Character LCDs may have a backlight, which may be LED, fluorescent, or electroluminescent. The nominal operating voltage for LED backlights is 5V at full brightness, with dimming at lower voltages dependent on the details such as LED color. Non-LED backlights often require higher voltages.

Character LCDs use a 16-contact interface, commonly using pins or card edge connections on 0.1 inch (2.54 mm) centers. Those without backlights may have only 14 pins, omitting the two pins powering the light. This interface was designed to be easily hooked up to the Intel MCS-51 XRAM interface, using only two address pins, which allowed displaying text on LCD using simple MOVX commands, offering cost effective option for adding text display to devices.

Vee (also V0): This is an analog input, typically connected to a potentiometer. The user must be able to control this voltage independent of all other adjustments, in order to optimise visibility of the display that varies i. a. with temperature and, in some cases, height above the sea level. With a wrong adjustment, the display will seem to malfunction.

R/W: In most applications, reading from the HD44780 is not necessary. In that case, this pin can be permanently connected to ground and no processor pins need to be allocated to control it.

In 8-bit mode, all transfers happen in one cycle of the enable pin (E) with all 8 bits on the data bus and the RS and R/W pins stable. In 4-bit mode, data are transferred as pairs of 4-bit "nibbles" on the upper data pins, D7–D4, with two enable pulses and the RS and R/W pins stable. The four most significant bits (7–4) must be written first, followed by the four least significant bits (3–0). The high/low sequence must be completed each time or the controller will not properly receive further commands.

Selecting 4-bit or 8-bit mode requires careful selection of commands. There are two primary considerations. First, with D3–D0 unconnected, these lines will always appear high (binary 1111) to the HD44780 since there are internal pull-up MOSFETs.

The same command is sent three times, Function Set with 8-bit interface D7–D4 = binary 0011, the lower four bits are "don"t care", using single enable pulses. If the controller is in 4-bit mode, the lower four bits are ignored so they cannot be sent until the interface is in a known size configuration.

In all three starting cases, the bus interface is now in 8-bit mode, 1 line, 5×8 characters. If a different configuration 8-bit mode is desired, an 8-bit bus Function Set command should be sent to set the full parameters. If 4-bit mode is desired, binary 0010 should be sent on D7–D4 with a single enable pulse. Now the controller will be in 4-bit mode and a full 4-bit bus Function Set command sequence (two enables with command bits 7–4 and 3–0 on subsequent cycles) will complete the configuration of the Function Set register.

The CGRAM is read/write memory used to encode up to 8 characters in the character generator. It consists of 64 fields at addresses 0 to 3F hex. Each field is 5 bits mapping to a row of pixels of each character. Each 8 fields in the CGRAM are used for each character. The lower 3 bits of the character codes from 0–7 and 8–15 select the groups of 8 fields in the CGRAM memory.

Reading and writing to the DDRAM is done by setting the RS input high during bus transfers. The DDRAM must also be selected by using the Set DDRAM address command which selects the DDRAM for access and also sets the starting address for DDRAM access.

Likewise reading and writing to the CGRAM is done by setting the RS input high during bus transfers. The CGRAM must also be selected by the Set CGRAM address command which selects the CGRAM for access and also sets the starting address for CGRAM access.

The execution times listed in this table are based on an oscillator frequency of 270 kHz. The data sheet indicates that for a resistor of 91 kΩ at VCC=5 V the oscillator can vary between 190 kHz and 350 kHz resulting in wait times of 52.6 µs and 28.6 µs instead of 37 µs. If a display with the recommended 91 kΩ resistor is powered from 3.3 volts the oscillator will run much slower. If the busy bit is not used and instructions are timed by the external circuitry, this should be taken into account.

The original HD44780 character generator ROM contains 208 characters in a 5×8 dot matrix, and 32 characters in a 5×10 dot matrix. More recent compatible chips are available with higher resolution, matched to displays with more pixels.

The 7-bit ASCII subset for the Japanese version is non-standard: it supplies a Yen symbol where the backslash character is normally found, and left and right arrow symbols in place of tilde and the rubout character.

A limited number of custom characters can be programmed into the device in the form of a bitmap using special commands. These characters have to be written to the device each time it is switched on, as they are stored in volatile memory.

Huang, Han-Way (2009). The HCS12 / 9S12: An Introduction to Software and Hardware Interfacing (2nd ed.). Delmar Cengage Learning. ISBN 978-1-4354-2742-6.

The closest thing to a standard is, unfortunately, for LCD panels that have controllers but no drivers. IIRC, a typical interface will have signals for phase polarity, frame clock, line clock, data clock and 4 data bits. Every line of pixels one should clock in enough groups of four pixels to fill the width of the display (extra bits will be ignored), driving the data clock high and low for each group. The drive the line clock high and low to strobe the line. The first line of each frame should have the frame clock high, and the phase polarity signal should toggle every frame.

The line clock signals, and those derived from them, must be sent at a uniform rate. The precise timing of the data clock signals, however, doesn"t matter provided that all the clocks happen for a line happen within the proper window. If you don"t have DMA, it may be possible to keep a small display happy and still have time to do something else, but refreshing the display will be a pain. If you do have DMA, however, and can manage a small CPLD to handle a few aspects of the timing, implementing the display that way may be very rewarding. I"ve done a display panel like that and achieved display-update performance superior to anything I could have done with a conventional display controller. I even achieved 4-level gray-scale by running the display at 100 frames/second and, every three frames, driving the display twice using one buffer and once with another.

The following documentation describes a potential way to drive HD44780-style 16x2 character LCDs in graphics mode by using a synchronized updating scheme and complementary special characters.

Character LCDs used in industrial machinery, test equipment and hobby projects are popular, long-lived and mostly based on Hitachi HD44780-style controllers (+ drivers) from multiple manufacturers:

The driving scheme for passive matrix displays depends on the arrangement of character groups and format (e.g. 5x8, 5x10, 5x11), but is most often seen to be 1:16-multiplexed with 1/5 level bias.

The 1:2 multiplex scheme below (taken from the NXP PCF2119 datasheet) conveys the idea in a more accessible fashion. STN pixels at the junction of row and column conductor stripes see a differential AC waveform. Small amplitudes don"t cause a pixel to switch, and in this case, pairs of frames must be generated complementarily to create a zero time average (no DC component).

With this in mind, the timing for a display with 1:16 multiplexing and 1/5 bias can be understood as cycling through all 16 rows, where only the first time slot associated with COM1 has the high levels contributing to cell switching.

Although HD44780-like controllers have an 8 bit parallel interface, the instruction decoding and memory access logic appears to be such that one command takes at least 37 µs at 270 kHz nominal clock speed, or 10 clock cycles. The write cursor (pointer) is post-incremented when a write command is performed, so at least one address update needs to precede or follow a burst write operation. Writing 16 consecutive characters costs a minimum of 170 clocks. Filling an 8x2 character region costs at least 180 clocks, highlighting the limitations of what is possible within the time duration of a single-line drive phase of 200 clocks.

In terms of organization, 16x2, 20x2 and 20x4 LCDs use additional drivers to add more column lines, which follow a bias scheme like the one discussed above. The application circuit below shows the daisy-chained configuration for up to 20x4 characters:

Note that only a 8x2 character block is driven by the controller itself. Pixel data for all remaining characters is transferred to daisychained driver ICs via a 3-wire synchronous serial interface.

This will be used later by inserting a resistor into the data (D) line from the controller to the first driver. A GPIO pin connected after the resistor is used for bi-directional interaction. Display controllers use a resistor-programmed internal oscillator, and injected data is synchronized to CL1, CL2 or M.

Just by looking at videos people have taken from their displays, tearing as a pre-requisite can be observed. As the bar graph is updated, blocks indicate data was updated during a frame.

The appetite for graphic memory access is perhaps best visible through the widespread fascination hobbyists and demoscene people have with the measly 8 custom characters available in all controllers. This well-documented feature is used by writing character code 0x00 .. 0x07 into DDRAM. The controller then gets pixel data from CGRAM and uses it analogous to CGROM data.

Although many controller manufacturers offer multiple CGROM variants (font sets) with special characters, there aren"t 2^40 different unique ones (128 GB) to display arbitrary 5x8 pixel blocks - needless to say the 40 bit character code might as well represent the pixel information itself.

If one could swap out a character before each line were serialized and sent to the column drivers however, each of 8 horizontal lines making up a 5x8 pixel character could be loaded from one of 32 characters. This subdivides the representation of an 5x8 arbitrary pixel block into 8 consecutively selected LUT characters. The image below shows placeholders for all LUT characters. The dark gray regions are ignored, while the relevant lines are drawn in black/light gray, depicting the required bit patterns.

These are exact matches, but some pixel combinations are left out. Luckily, there are still 8 custom characters available to complement the CGROM set.

With the exception of the first LUT line, all LUT lines have <= 8 missing characters, so CGRAM codes can be inserted, and CGRAM pixels defined accordingly by copying the sought-after 5-pixel combinations to their corresponding y positions. These are the custom characters derived from the A02 font set (with some artistic license, as 5-pixel lines of the same y position are interchangeable):

The following LUT example depicts how 5x8 graphics content is mapped to 8 LUT characters displayed in sequence, and of which only one line is used to compose the ouput on the LCD panel.

To investigate whether there is a window of opportunity to write LUT codes into DDRAM and to reset the DDRAM cursor periodically and synchronized to the bit pattern generation, an reduced section of the functional block diagram from the HD44780 datasheet is presented below.

DDRAM addresses come from the instruction decoder, as well as from the timing generator (not necessarily indicated in all datasheets). The 8 bit data bus is necessarily controlled by the MPU (or instruction decoder). As the data bus is shared, access is likely to be interleaved.

4-bit line positions (0..7 for 5x8 characters, 0..10 for 5x11) need to come from the timing generator, as the memory outputs are only 5 bit wide towards the serializer.

The timing generator and MPU need to be synchronized to ensure appropriate phasing of data transfers into the serializer unit. Some arrows are rather hand-waivy. The more familiar "reset" signal doesn"t point to anything in particular, and it is implied that it connects to multiple blocks. Both "Instruction decoder" arrows have an unspecified bit width, but they"re not 1 bit wide (not plausible for address data to counter). So essentially there is a possibility that multiple lines are routed to the Timing Generator block, allowing an operation to reset the Timing Generator. Hopefully DISPLAY ON/OFF triggers such a reset.

Other datasheets are even less clear about the actual function or existence of Instruction Decoder outputs and interconnectedness. Maybe a die shot would help to clarify.

This leads to believe that the Parallel/Serial converter unit is also buffered and in part controlled by the MPU / instruction decoder. Depending on the address counter (< 16), CGRAM 5-bit data is used instead of CGROM 5-bit data. Additionally, the order of DDRAM readout is dependent on the display layout stored in the MPU, so the MPU is continuously involved in loading DDRAM data.

The serializer needs to be filled with fresh data for every line, as the line selection already happens during CGRAM / CGROM access and no full CGROM/CGRAM 2D image is copied. The functional block diagram shows a 40 bit shift register connected to the serializer. Strangely, the "parallel/serial converter" has a 40 bit wide output bus, so it essentially stores the eight 5-bit values loaded from CGRAM/CGROM.

The maximum size is 80 displayed characters, each measuring 5x8 pixels, for a total of 3200 pixels. Divide that by the maximum of 16 COM lines and each line has to have 200 pixels. This number shows up above as the "200 clocks" for which one COM line is driven in a 1:16 multiplexing scheme. So without measuring, one can derive that the serializer is clocked at the full oscillator frequency. It seems plausible that the serializer would then run continuously but only fed a part of the time when displays are smaller.

We now also know that the MPU has 5 clock cycles to get the CGROM/CGRAM data into the parallel buffer of the parallel/serial converter, and for a 20x4 display, serializer data loading has to run continuously.

The MPU is thus twice as fast when transferring the data as one could write it into DDRAM. Timing-wise, one needs to start writing right at or behind the internal reading address. Assuming an instruction or data write operation takes 11 clocks, 16 LUT characters + 1 instruction byte can be written and processed, unlocking 16x2 * 5*8 graphics mode. That"s 80x16 (1280) pixels, give or take.

It should also be noted that when limiting oneself to an 8x2 character block and 1/16 multiplexing, DDRAM 0x00 .. 0x07 and 0x40 .. x047 can also be directly filled with custom chracters 0 .. 7. Instead of changing character codes in DDRAM, write operations can update CGRAM patterns in the corresponding custom character lines, creating full pixel access. The second set of rows (COM8..15) start at CGRAM line 0, 1, ... again, making custom characters a just-in-time video buffer.

Furthermore, when injecting data into the serial interface to the daisy-chained extension drivers, only 8 characters + 1 command byte need to be written, further relaxing the timing and creating leeway for "software" synchronization. The latter relies on the assumption that a DISPLAY ON/OFF command resets the row counter in the timing generator. HD44780-like controllers offer an external clock option for jitter- and drift-free operation, but adding wires for extension driver CL1, CL2, M and D lines seems a lot more useful. The timing seems to be too critical to rely on RC oscillator accuracy anyway, and even though that makes it an invasive modification, it is being rewarded with a pathway to 20x4 character graphic mode.

With a 4k7 resistor placed over a cut through the D line between main controller and the first auxiliary driver, a GPIO can be connected on the driver side for bidirectional I/O. CGROM or custom characters can then be read as they are being sent out to column drivers and synchronized to, before the GPIO is switched to push-pull mode, taking over the role as pixel data source.

Presenting pixel data to extension drivers only, and also using them for row driving, seems to have been a product reality around 1985, as the picture below shared by AVRFreaks user ossi evidences:

so there really should be nothing holding us back morally from modifying modern displays for pixel data injection synchronous to a clock provided by a controller.

Arduino-related projects are very popular and, like Raspberry Pi, it is one of the most used Free Hardware projects among companies. That is why we are going to talk about one of the most popular combinations among Arduino users: LCD + Arduino.

The LCD display is an increasingly economical and accessible accessory, which makes it a great option to accompany our Arduino board. But Can an LCD screen be used with our Arduino board? What projects can be used with LCD and Arduino, is this combination worth using?

Novice users are unaware of what LCD stands for, even though they will have seen it more than once in their lifetime. LCD stands for Liquid Crystal Display, or what comes to be Liquid Crystal Display. A small or large screen that many of us have known in various devices such as alarm clocks, clock screens, calculators, etc ... Endless electronic devices that are expanded thanks to the combination of LCD + Arduino and Free Hardware.

LCD screens are compatible with any Free Hardware, including Arduino Project boards, although they require that the boards have certain connectors or pins to make the connection between the electronics board and the LCD screen.

A priori, there is no impediment to using different LCD screen sizes. In other words, the same Arduino board can use a 5-inch, 20 “LCD screen or a 5 × 2 character size, to speak of a small size. But we must be aware thatArduino board is not the same as a graphics card or motherboard, so the message to be displayed on a screen will not work the same on a small screen as on a large screen, as long as it is the same Arduino board.

If you have enough pins and pins compatible with the above, LCD screen will work perfectly with Arduino board. So it is always advisable to check the pins of both devices to make sure that the connection exists. In any case, it is rare for the Arduino board that cannot be connected to an lcd display and in case of having such a situation, there are different lcd modules on the market that are easily connected to Arduino and whose cost is quite affordable.

El Line LCD is a type of screen that shows information through lines. The information is situated in lines and we cannot get out of that frame. This type of LCD is the most widely used, economical and well-known but it is also the type of lcd that gives less play, since it only shows certain information and is usually just text.

El dot lcd It works almost the same as the previous type of lcd, but unlike the previous one, in the lcd by points we have a matrix of points. Thus, in this type of lcd we can place the text and even images anywhere on the lcd screen. What"s more we can have several font sizes within the same lcd screen, something that does not happen in the lcd display of lines, whose size must always be the same.

El OLED display It is for many a type of display of their own while for others it is within the types of lcd. The OLED Display is a screen that shows us information but its construction is different from that of the LCD screen since uses led diodes with organic components for its creation. Unlike the previous types, OLED displays offer higher resolution, color and lower energy consumption. Like computer monitors or dot lcd, OLED screens use the matrix of dots or pixels (since we can use several colors on the same display) to display content.

El LED or LCD Led display is similar to OLED Display, but led diodes do not contain organic elements. Its performance is not as high as the OLED display but it does offer more resolution than the dot LCD screen and offers color.

El TFT display is the latest type of lcd on the market. We can say that the TFT display uses pixels like computer monitors or televisions and that we can emit any type of information through these screens. Its energy consumption is higher than any of the previous types hence small sizes are used. The size of these displays is measured in inches unlike some of the other types of displays. They are measured by characters or by screen width.

Thanks to online commerce we can find countless models of lcd displays, but only a few are the most popular. This popularity is due to its easy acquisition, its price, its performance or simply its quality.. Here we talk about these models:

This display comes from the old Nokia 5110 mobile phones. The LCD of these mobiles outperformed the mobile and the company has continued to sell this display for its own use. The screen is monochrome and is Lineas LCD type. The Nokia 5110 display offers 48 rows and 84 columns. Its power is such that it offers the ability to view images, although not efficiently. Its performance is very good although we will need to use backlighting to be able to correctly view the screen, in general it is usually accompanied by this backlighting although there may be modules that lack this function. The display uses a Philips PCD8544 driver. The Nokia 5110 LCD screen can be found at shops for 1,8 euros.

The Hitachi HD44780 LCD It is a module created by the manufacturer Hitachi. The lcd panel is monochrome and is line type. We can find a model with 2 lines of 16 characters each and another model with 4 lines of 20 characters each. We usually find the Hitachi HD44780 LCD display in any store but it may also happen that we only find the Hitachi HD44780 controller without a screen, the price can help us in this situation, the cost being screen plus controller for 1,70 euros and only the 0,6 euro driver.

This lcd display is OLED type. The I2C OLED LCD is a one-inch size monochrome OLED screen that connects to the Arduino via the I2C protocol, this protocol uses a bidirectional bus that allows us to save pins, being necessary four pins in front of the necessary ones previously mentioned. The driver for this LCD screen is generic so we can use free libraries for its use. The price of this model is not as cheap as the previous models but if it is affordable by many users, we can find for 10 euros a unit.

The E-Ink LCD screen uses electronic ink to display information. Like the rest of the models, uses the I2C protocol to communicate with Arduino. The screens are of the TFT type but using electronic ink which makes consumption considerably lower but without losing resolution. Although there are no color screens (at the moment), they are all in black and gray scale.

As a curiosity about this model of lcd screens, we have to say that price and size are united. We can find different sizes and the bigger the size, the more expensive the screen. Thus, 1 or 2,5 inch E-Ink screens They have a price of 25 euros per unit. The larger size panels can reach 1.000 euros per unit.

The connection between an LCD screen and Arduino is very simple. In principle we have to follow the pins mentioned above and connect them to the Arduino board. The connection diagram would be the following:

But it is not the only thing we have to take into account to connect the LCD screen to Arduino. What"s more we have to use a library that will help us to give the program that we create the necessary code to make it work correctly with the screen. This bookstore it"s called LiquidCrystal.h and it can be obtained for free throughthe official Arduino website. This library must be used like the rest of the libraries, invoking it at the beginning of the code as follows:

Continuing with the above, we have to ask ourselves if it is really convenient to have an LCD screen and Arduino for our personal project or project. Personally, I think that for certain projects it is necessary and for the rest of them it is something more personal than necessary. For example, we can talk about the latest models of 3D printers, models that only add in some cases the LCD display and nothing else, but the price of the model is significantly more expensive.

In these cases I do not think that an LCD display is needed, but this is not the case in certain projects where the LCD display is very important. Examples of the latter are projects such as watches, a game console or simply a GPS locator. Projects that need to have a graphical interface to function effectively. What we say may be silly, especially for the most expert users, but any component can make any project more expensive and even make it unviable. Hence, it is important to assess whether our project should have an LCD screen or not.

This website is using a security service to protect itself from online attacks. The action you just performed triggered the security solution. There are several actions that could trigger this block including submitting a certain word or phrase, a SQL command or malformed data.

A Liquid Crystal Display (LCD) can be of the character type or graphics type. Graphic LCD displays have a matrix of pixels that can be used to display text and graphics, e.g. 128 by 64 pixel display. When starting electronics, a character LCD will usually be used.

Character LCDs can display characters only and are divided into rows of characters. For example a 2 by 16 character LCD display has two lines that can display 16 characters each. An example of a 2 × 16 character display is shown below.

LCDs are available with or without a backlight. A backlight is just a light in the LCD that lights up the display making it easier to read in low light conditions.

There are a number of character LCDs based on the Hitachi HD44780 LCD controller and driver IC. These displays are software compatible and available from several different manufacturers. There are even pin compatible character LCDs that are available from different manufacturers. Always check the datasheet from the manufacturer to make sure of the pin numbering and pin functions of the LCD display that you are going to use.

It is possible that other displays are also compatible with this one. If a backlight is not present, then pin 1 and 2 may be missing. Other LCDs may have the pins at the top and pin numbering may start with 1 on the left.

There are a number of different kinds of displays that can be driven by a microcontroller. This repository contains examples for many of them, along with information about display technologies and some of the more popular libraries for controlling them.

Multi-Segment LED display - There are many models of multi-segment LED displays, including the classic 7-segment LEDs, alphanumeric displays, dot-matrix diplays, bar graph displays, RGB LEDs, and others. What these share in common is that they will have either a common-cathode or common-anode structure. Common cathode LEDs have multiple anodes, one for each LED segment, and one cathode for all. common anode LEDs have a single anode and multiple cathode for all the segments. Driving these displays requires a control pin for each LED segment. They are usually driven by a multiplexer or LED driver, which can provide both a common interface for all the LEDs (such as an SPI or I2C interface), and a controlled current supply for all the LEDs.

Broadcom/Avago’s HCMS-29xx display is multi-segment LED display that has several 5-7 LED matrices with a synchronous serial interface. It has the smallest visibly discrete LEDs in its display that I have encountered.

LCD - Liquid crystal display. LCDs are made up of long-chain molecules in a state between crystal and liquid. When a charge is applied, the molecules align, acting as a polarizer. When paired with a second polarizer, they can either block light or allow it to pass through, appearing either light or dark. A grid of these can form a single-color display. Liquid crystals do not emit light, so a backlight is required to light them up. They come im low-resolution, passive-matrix displays which are usually monochrome or higher-resolution, active-matrix screens which have higher resolution and are usually full color.

OLED - an OLED screen replaces the liquid crystal with a matrix of organic LEDs. This eliminates the need for a backlight, since each pixel generates its own light. For more on OLEDs, see this introduction from ehergy.gov. CNET provides this comparison of LCD vs OLED displays.

ePaper - ePaper displays use a matrix of tiny capsules which are black or colored on one side, and white on the other. Applying a charge to each capsule causes it to turn one way or the other. Unlike LCD or LED displays, ePaper displays maintain their state when powered off. ePaper displays cannot be refreshed as fast as LCD or LED, however. ePaper displays are typically not backlit, and require external lighting. eInk, the primary maker of ePaper displays, has a good FAQ on the technology. Visionect.com has a helpful illustrated explanation as well.

LCD and OLED screens drive their pixels in one of two ways. A passive matrix uses a grid of wires which control each pixel using a row-column scanning method. Voltage is applied to each column in sequence. Then the rows are scanned. If the pixel on that column at a given row should be on, then the row wire voltage is taken low to create a voltage difference, and the pixel turns on. An active matrix uses a grid of thin film transistors (TFT) instead of a row-column scanning apparatus. TFTs allow for greater pixel density and therefore sharper image quality and better response time for each pixel. Jameco offers a good explanation of passive vs. active matrix driver technology.

The oldest form of LCD display, patented in the 1980’s, is known as Twisted Nematic (TN) LCD, and has limits to its viewing angle. Newer LCD technologies such as in-plane switching (IPS) or plane-to-line switching (PLS) afford wider viewing angles and brighter screens.

There are a number of common display driver ICs on the market. Typically a driver IC will be capable of controlling many different sizes and shapes of display, if they are of the same class. For example, you’ll see many TFT displays that use Sitronix’ driver ICs, notably the ST7735 and ST7789. Ilitek’s ILI9225 chip is also common in TFTs. This means that libraries written for one vendor’s display are likely to work for displays from another vendor, if they use the same chipset. This can be convenient, as it means you can sometimes choose the library whose API you find easiest to work with.

There are many LED driver ICs on the market, which give you control over multiple LED segments from a single synchronous serial interface. Some include PWM control over each channel as well. Popular ones include Maxim’s MAX7219 and Texas Instruments’ TLC5947. Many of the hobbyist electronic vendors carry breakout boards for these chips.

Recently, drivers for LEDs have reduced in size to the point where a driver can drive a single pixel. Usually made of three to four LEDs and a single driver, these are very popular with electronics hobbyists. For more on these, see this repository.

Displays for microcontrollers use a variety of control interfaces. The most common are the ones you see for other electronic modules as well: synchronous serial interfaces like I2C and SPI, or asynchronous serial interfaces. also feature parallel interface, requires a large number of I/O pins from your controller.

BUSY - an output pin to indicate that the display controller is busy. connects to whicheve pin the microcontroller has assigned for this function. This pin is less common on TFT displays than on ePaper displays.

Backlight - most TFT screens have a pin which enables or disables the backlight of the screen. The naming for this is not standardized: BLK, LITE, TE are all in use. Read the module’s datasheet for details.

Adafruit tends to add an SD card reader and sometimes a static RAM chip to its modules, which are also controlled by the SPI bus. When these are present, you’ll see chip select pins for them, usually labeled CCS or SCDS for the SD card and SRCS for the SRAM. If you’re not using the SD card or SRAM in your application, you won’t need these.

Note: the electronics industry has used the terms “master/slave” to refer to controller devices and peripheral devices for decades without regard for the historical context of, and offense caused by, those terms. As a result, you will see the terms MOSI/MISO/SS in data sheets to refer to the pins of an SPI device While a modern standard naming scheme has not yet emerged to replace these, there are proposals in discussion. The Open Source Hardware Association has this proposal, for example. Make Magazine has this proposal. The debate is not resolved, and you will likely see some variations on the terms. The SDO, SDI, and SCK terms are the most widely accepted terms with the least historical baggage, but unfortunately, it’s still necessary to be aware of the other possible terms for pins in SPI.

Hitachi HD44780 LCD display. See the Arduino LiquidCrystal library. These 2x16 character LCD displays are ubiquitous in the hobbyist market and come in many starter kits for the Uno. They are a passive-matrix LCD with a parallel interface (6 pins) that runs on 5 volts. They will typically not run on 3.3 volts. Each character is a 5x7 pixel matrix, so these are very low-resolution displays. They can usually be foung for $10-$15, which was a bargain in the early Arduino days. Nowadays, if you need an inexpensive 2-line display, some of the OLED displays like the SSD1306 are a better bargain.

There are some display modules which have an asynchronous serial (UART) interfaces. These typically have a microcontroller on the display module itself, which is interfacing with one of the types of interfaces above. These modules typically have a communications protocol that is unique to the vendor. They are convenient, but more expensive than their synchronous serial or parallel counterparts.

Finding the right display library for your Arduino or Arduino-compatible display can be challenging. Vendors who design and sell their own breakout boards tend to publish libraries that are compatible with their own boards. Smaller vendors may not make their own libraries, relying on third-party libraries instead. The Arduino site lists over 300 display-related libraries. The ease-of-use and adaptability of those libraries varies widely. The ones I’ve found most useful are Adafruit’s GFX library and Oli Kraus’ U8g2 library.

Since there is a relatively small number of driver chip manufacturers (Hitachi, Ilitek, Solomon-Systech, and Sitronix among them), different vendors’ boards often use the same driver hardware. This means that the libraries from one vendor can support the hardware from another. When you shop for displays, it’s worthwhile to check what the driver is for each one, and see if there’s a compatible library from your favorite library writer.

Adafruit_GFX is a hardware-independent graphics library written to work with all the Arduino-compatible displays that Adafruit sells. They complement this with display specific libraries like Adafruit_SSD1306 for SSD1306 OLED libraries, Adafruit_EPD for ePaper displays, Adafruit_ST7735 for some TFT libraries, and others. The advantage of the GFX library is that you get a common drawing API regardless of which display you’re using. It uses the Arduino Printable interface too, so commands like print() and println() work with this library just like they do in the serial monitor. There’s a good guide to the GFX library as well. Sparkfun’s got their own complement to the GFX library, Hyperdisplay.

u8g2 is designed as a universal library for many different displays. It supports a wider range of displays than any other I’ve used so far. It has its own graphics API which is more or less similar to Adafruit’s, and a wide font set as well. There’s also U8g2_for_Adafruit_GFX, a library which allows you to add U8g2 fonts to any Adafruit_GFX-based library.

If you plan on using an LCD with your Raspberry Pi, there’s a good chance you’ll need to program it in Python at some point. Python is probably the most popular programming language for coding on the Raspberry Pi, and many of the projects and examples you’ll find are written in Python.

In this tutorial, I’ll show you how to connect your LCD and program it in Python, using the RPLCD library. I’ll start with showing you how to connect it in either 8 bit mode or 4 bit mode. Then I’ll explain how to install the library, and provide examples for printing and positioning text, clearing the screen, and controlling the cursor. I’ll also give you examples for scrolling text, creating custom characters, printing data from a sensor, and displaying the date, time, and IP address of your Pi.

BONUS: I made a quick start guide for this tutorial that you can download and go back to later if you can’t set this up right now. It covers all of the steps, diagrams, and code you need to get started.

You can also connect the LCD via I2C, which uses only two wires, but it requires some extra hardware. Check out our article, How to Setup an I2C LCD on the Raspberry Pi to see how.

There are two ways to connect the LCD to your Raspberry Pi – in 4 bit mode or 8 bit mode. 4 bit mode uses 6 GPIO pins, while 8 bit mode uses 10. Since it uses up less pins, 4 bit mode is the most common method, but I’ll explain how to set up and program the LCD both ways.

Each character and command is sent to the LCD as a byte (8 bits) of data. In 8 bit mode, the byte is sent all at once through 8 data wires, one bit per wire. In 4 bit mode, the byte is split into two sets of 4 bits – the upper bits and lower bits, which are sent one after the other over 4 data wires.

Theoretically, 8 bit mode transfers data about twice as fast as 4 bit mode, since the entire byte is sent all at once. However, the LCD driver takes a relatively long time to process the data, so no matter which mode is being used, we don’t really notice a difference in data transfer speed between 8 bit and 4 bit modes.

If this is your first time writing and running a Python program, you might want to read How to Write and Run a Python Program on the Raspberry Pi, which will explain everything you need to know to run the examples below.

The RPLCD library can be installed from the Python Package Index, or PIP. It might already be installed on your Pi, but if not, enter this at the command prompt to install it:

The example programs below use the Raspberry Pi’s physical pin numbers, not the BCM or GPIO numbers. I’m assuming you have your LCD connected the way it is in the diagrams above, but I’ll show you how to change the pin connections if you need to.

Let’s start with a simple program that will display “Hello world!” on the LCD. If you have a different sized LCD than the 16×2 I’m using (like a 20×4), change the number of columns and rows in line 2 of the code. cols= sets the number of columns, and rows= sets the number of rows. You can also change the pins used for the LCD’s RS, E, and data pins. The data pins are set as pins_data=[D0, D1, D2, D3, D4, D5, D6, D7].

The text can be positioned anywhere on the screen using lcd.cursor_pos = (ROW, COLUMN). The rows are numbered starting from zero, so the top row is row 0, and the bottom row is row 1. Similarly, the columns are numbered starting at zero, so for a 16×2 LCD the columns are numbered 0 to 15. For example, the code below places “Hello world!” starting at the bottom row, fourth column:

The RPLCD library provides several functions for controlling the cursor. You can have a block cursor, an underline cursor, or a blinking cursor. Use the following functions to set the cursor:

Text will automatically wrap to the next line if the length of the text is greater than the column length of your LCD. You can also control where the text string breaks to the next line by inserting \n\r where you want the break to occur. The code below will print “Hello” to the top row, and “world!” to the bottom row.

This program will print the IP address of your ethernet connection to the LCD. To print the IP of your WiFi connection, just change eth0 in line 19 to wlan0:

Each character on the LCD is an array of 5×8 of pixels. You can create any pattern or character you can think of, and display it on the screen as a custom character. Check out this website for an interactive tool that creates the bit array used to define custom characters.

First we define the character in lines 4 to 12 of the code below. Then we use the function lcd.create_char(0-7, NAME) to store the character in the LCD’s CGRAM memory. Up to 8 (0-7) characters can be stored at a time. To print the custom character, we use lcd.write_string(unichr(0)), where the number in unichr() is the memory location (0-7) defined in lcd.create_char().

To demonstrate how to print data from a sensor, here’s a program that displays the temperature from a DS18B20 Digital Temperature Sensor. There is some set up to do before you can get this to work on the Raspberry Pi, so check out our tutorial on the DS18B20 to see how.

In general, you take the input variable from your sensor and convert it to an integer to perform any calculations. Then convert the result to a string, and output the string to the display using lcd.write_string(sensor_data()):

Well, that about covers most of what you’ll need to get started programming your LCD with Python. Try combining the programs to get some interesting effects. You can display data from multiple sensors by printing and clearing the screen or positioning the text. You can also make fun animations by scrolling custom characters.