Displaying custom characters on an I2C LCD with a Raspberry PI Pico and MicroPython

In this article we look at creating and displaying custom characters on an I2C 16×2 LCD to a raspberry Pi Pico

 

Parts Required

 

Name	Link
Pico	Raspberry Pi Pico Development Board
I2C lCD	Aliexpress link
Connecting cables	Aliexpress product link Lysee 3D Printer Parts & Accessories – AHT20 Temperature and Humidity Sensor Module DHT11 Upgrade I2C XD Humidity Sensor Probe – (Color: Green) Ebay link

 

Schematic/Connection

To connect the display to your Raspberry PI Pico requires just 4 wires, you just need to wire the Vcc and GND PINs from display to VBuS and a GND PINs of RPI Pico, then SDA and SCL PINs from the module to suitable SDA and SCL PINs from Raspberry PI Pico

Here is a layout in fritzing to show this

 

Character generation

You need to visit https://maxpromer.github.io/LCD-Character-Creator/

In the interfacing option select I2C and in the data type option select hex

Then go and design your characters by clicking the various boxes, you can see an example that I designed in this image.

Code Example

I use thonny for all development – we have kept this information from our 16×2 LCD article

Now its important to verify the I2C address of your LCD

import machine
sdaPIN=machine.Pin(0)
sclPIN=machine.Pin(1)
i2c=machine.I2C(0,sda=sdaPIN, scl=sclPIN, freq=400000)
devices = i2c.scan()
if len(devices) == 0:
 print("No i2c device !")
else:
 print('i2c devices found:',len(devices))
for device in devices:
 print("Hexa address: ",hex(device))

You will see the I2C address in the REPL

You then need to copy 2 libraries to your Pico filesystem

In Thonny, go to top menu File => Save Copy => Raspberry Pi Pico and save each file to the board with the same name as downloaded and with a .PY extension when saving it to the board.

https://github.com/T-622/RPI-PICO-I2C-LCD/blob/main/lcd_api.py

https://github.com/T-622/RPI-PICO-I2C-LCD/blob/main/pico_i2c_lcd.py

In this example we display the 3 custom characters that we designed earlier

We use  this command

lcd.custom_char(Num, bytearray([HEX chars]))) – Num can be any integer 0 – 8 (Writing to CGRAM locations) merely used for numbering.

import utime

from machine import I2C
from lcd_api import LcdApi
from pico_i2c_lcd import I2cLcd

I2C_ADDR     = 0x27
I2C_NUM_ROWS = 2
I2C_NUM_COLS = 16

i2c = I2C(0, sda=machine.Pin(0), scl=machine.Pin(1), freq=400000)
lcd = I2cLcd(i2c, I2C_ADDR, I2C_NUM_ROWS, I2C_NUM_COLS)

#clear screen
lcd.clear()
lcd.custom_char(0, bytearray([0x1F,
  0x0E,
  0x04,
  0x1F,
  0x1F,
  0x04,
  0x0E,
  0x1F]))
lcd.custom_char(1, bytearray([0x1F,
  0x04,
  0x04,
  0x0E,
  0x0E,
  0x04,
  0x04,
  0x1F]))
lcd.custom_char(2, bytearray([0x00,
  0x1B,
  0x1B,
  0x11,
  0x11,
  0x1B,
  0x1B,
  0x00]))
lcd.move_to(0,0)
lcd.putchar(chr(0))
lcd.move_to(1,0)
lcd.putchar(chr(1))
lcd.move_to(2,0)
lcd.putchar(chr(2))
utime.sleep(5)

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