The most common controller of multi-line character displays is the HD44780. There are several Raspberry Pi LCD display sizes (8×2, 16×2, 20×4, etc.) that run with it. In this tutorial, I will show how to use a 16×2 character display and also run a test script.
A few words said in advance: In this tutorial, all pins are addressed directly, which occupies quite a few GPIOs. Another method is the connection via I2C.
Required Hardware Parts
The following parts are required:
- Display with a HD44780 controller
- Jumper Cable
- A resistor or alternatively a potentiometer (to control the backlight)
In this case, I refer to the pin numbering (GPIO.BOARD), not to the GPIO numbers:
|LCD Pin||to RPi GPIO||Description|
|1. VSS||Pin 6 (GND)||Supply Voltage (ground)|
|2. VDD||Pin 2 (5V)||Supply Voltage 5V|
|3. V0||Pin 6 (GND)||Contrast Voltage|
|4. RS||Pin 7 (GPIO4)||Register Selection (0: Command Register, 1: Data Register)|
|5. RW||Pin 6 (GND)||Read/Write (0: Write Modus, 1: Read Modus)|
|6. E||Pin 11 (GPIO17)||Clock Edge|
|7. D0||–||Data Line 0|
|8. D1||–||Data Line 1|
|9. D2||–||Data Line 2|
|10. D3||–||Data Line 3|
|11. D4||Pin 12 (GPIO18)||Data Line 4|
|12. D5||Pin 15 (GPIO22)||Data Line 5|
|13. D6||Pin 16 (GPIO23)||Data Line 6|
|14. D7||Pin 18 (GPIO24)||Data Line 7|
|15. A||Pin 2 (5V) (mit Poti)||Backlight Anode|
|16. K||Pin 6 (GND)||Backlight Cathode|
Schematically, the whole thing looks like this:
The backlight can be adjusted by turning the potentiometer. Some displays cannot stand 5V for the backlight, so you should either look at the datasheet or at least always connect a 470Ω – 510Ω resistor.
Testing the Raspberry Pi LCD Display
You can either view the script I used here or just download it and try.
wget http://www.tutorials-raspberrypi.de/wp-content/uploads/scripts/hd44780_test.py chmod +x hd44780_test.py python hd44780_test.py
If you have chosen a different display or pin assignment, do not forget to adapt the script.
Through the simple control, you can create different scripts, which, for example, show the status of the Pi.
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If you have contrast issues or need to edit the code for a 20×4 screen i’ve made a youtube clip to fix some issues i had after following the tutorial. https://www.youtube.com/watch?v=geEA-5f74Gk