README.md

   1 # RPI-PICO-I2C-LCD
   2 This is a project which adapts code from another user to allow usage of the PCF8574 I2C lcd backpack for either 20x4 or 16x2 lcd screens.
   3
   4 Credit: https://github.com/dhylands/python_lcd/tree/master/lcd mostly to Dave Hylands for the basic api and lcd driver code.
   5
   6 This is code adaptded for micropython and the Raspberry Pi PICO specifically.
   7
   8 Usage:
   9 - Download all 3 .py files included.
  10 - Open Thonny IDE with the 3 files
  11 - Make pin edits or setup changes (See below for options)
  12 - DO NOT EDIT FILE NAMES!
  13 - In Thonny, go to top menu File => Save Copy => Raspberry Pi Pico and save each .py file to the board.
  14 - Switch to the main.py and click run. This should be able to initalize the LCD display if settings are right.
  15 - If you get errors, see below for a known list of errors and their fixes
  16
  17 Requirements:
  18 - 3.3 - 5V level translator. This is crucial to encure the lcd recieves the commands properly. I recommend this: https://www.adafruit.com/product/757 (Must be Bi-Directional)
  19 - PCF8574 I2C LCD backpack. (These are common to find)
  20
  21 Setup Changes:
  22 - Make sure the top address is set correctly!
  23 Use this small program to scan for I2C devices:
  24
  25 import machine
  26 sda=machine.Pin(0)
  27 scl=machine.Pin(1)
  28 i2c=machine.I2C(0,sda=sda, scl=scl, freq=400000)
  29 print(i2c.scan())
  30
  31 - Once you get an address through the console (REPL), this will be in decimal and not hex. You can convert the decimal to hex or simply put a decimal address in the setup.
  32 in my case, the decimal addr. was 39 which converts to 0x27 in hex.
  33 - Ensure that your SCL and SDA pins are selected properly in accordance with the Pico's pin table. These connect to the low voltage side of the translator with a 3.3V Reference from the board. The high voltage side gets a 5V reference from the VBUS pin of the Pico.
  34 - Finally, assure the I2C_NUM_ROWS and I2C_NUM_COLS are set properly!
  35
  36 Usage:
  37 Printing is simple :lcd.putstr("") This requires a string input! if you want to feed a changing value such as a temperature, it must be: lcd.putstr(str(Variable))
  38
  39 Errors:
  40 OSERROR : 5 (This is quite a common error, 5 means I/O error. Check Your connections. This means codes can't be sent or recieved ensure SCL and SDA are properly connected through the level translator!