In this tutorial, we will learn how to connect and use a 16×2 LCD display with Raspberry Pi Pico to provide a user interface. The display is a very famous electronics component, There are many different types of displays in the market that have their own features Similarly 16×2 LCD has its own quality. We used it earlier with Arduino board but today we will use it with Raspberry Pi Pico board With Python Code. So let’s get started
Required Components
- Raspberry Pi Pico
- 16X2 LCD
- Jumper cable
What is a 16×2 Display?
LCD (Liquid Crystal Display) screens are one of the simplest and cheapest ways to provide applications for displaying various parameters and statuses of the system. The 16×1 display unit will have 16 characters and be in one line. The 16×2 LCD will have 32 characters in total 16in 1st line and another 16 in 2nd line
- LCD 16×2 can be used in 4-bit mode or 8-bit mode.
- LCD consists of 16 rows and 2 columns of 5×7 or 5×8 LCD dot matrices.
Circuit Diagram for 16×2 LCD display with raspberry pi pico
The circuit diagram between the Raspberry Pi Pico and I2C 16×2 LCD is very simple as shown below in the schematic.
- Connect the LCD VCC & GND Pin to Raspberry Pi Pico 5V & GND
- Connect the SDA & SCL pin of the LCD to Raspberry Pi Pico GP26 & G27 respectively.
Library & Source Code
I used the Thonny IDE that supports Micropython on the Raspberry Pi Pico. Firstly You need to Add libraries
- The “i2c_lcd_lib.py” driver library
- The “lcd_api.py” driver library
Copy all the below codes and then save all of the 3 codes in the Raspberry Pi Pico Board.
lcd_api.py
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"""Provides an API for talking to HD44780 compatible character LCDs.""" import time class LcdApi: """Implements the API for talking with HD44780 compatible character LCDs. This class only knows what commands to send to the LCD, and not how to get them to the LCD. It is expected that a derived class will implement the hal_xxx functions. """ # The following constant names were lifted from the avrlib lcd.h # header file, however, I changed the definitions from bit numbers # to bit masks. # # HD44780 LCD controller command set LCD_CLR = 0x01 # DB0: clear display LCD_HOME = 0x02 # DB1: return to home position LCD_ENTRY_MODE = 0x04 # DB2: set entry mode LCD_ENTRY_INC = 0x02 # --DB1: increment LCD_ENTRY_SHIFT = 0x01 # --DB0: shift LCD_ON_CTRL = 0x08 # DB3: turn lcd/cursor on LCD_ON_DISPLAY = 0x04 # --DB2: turn display on LCD_ON_CURSOR = 0x02 # --DB1: turn cursor on LCD_ON_BLINK = 0x01 # --DB0: blinking cursor LCD_MOVE = 0x10 # DB4: move cursor/display LCD_MOVE_DISP = 0x08 # --DB3: move display (0-> move cursor) LCD_MOVE_RIGHT = 0x04 # --DB2: move right (0-> left) LCD_FUNCTION = 0x20 # DB5: function set LCD_FUNCTION_8BIT = 0x10 # --DB4: set 8BIT mode (0->4BIT mode) LCD_FUNCTION_2LINES = 0x08 # --DB3: two lines (0->one line) LCD_FUNCTION_10DOTS = 0x04 # --DB2: 5x10 font (0->5x7 font) LCD_FUNCTION_RESET = 0x30 # See "Initializing by Instruction" section LCD_CGRAM = 0x40 # DB6: set CG RAM address LCD_DDRAM = 0x80 # DB7: set DD RAM address LCD_RS_CMD = 0 LCD_RS_DATA = 1 LCD_RW_WRITE = 0 LCD_RW_READ = 1 def __init__(self, num_lines, num_columns): self.num_lines = num_lines if self.num_lines > 4: self.num_lines = 4 self.num_columns = num_columns if self.num_columns > 40: self.num_columns = 40 self.cursor_x = 0 self.cursor_y = 0 self.backlight = True self.display_off() self.backlight_on() self.clear() self.hal_write_command(self.LCD_ENTRY_MODE | self.LCD_ENTRY_INC) self.hide_cursor() self.display_on() def clear(self): """Clears the LCD display and moves the cursor to the top left corner. """ self.hal_write_command(self.LCD_CLR) self.hal_write_command(self.LCD_HOME) self.cursor_x = 0 self.cursor_y = 0 def show_cursor(self): """Causes the cursor to be made visible.""" self.hal_write_command(self.LCD_ON_CTRL | self.LCD_ON_DISPLAY | self.LCD_ON_CURSOR) def hide_cursor(self): """Causes the cursor to be hidden.""" self.hal_write_command(self.LCD_ON_CTRL | self.LCD_ON_DISPLAY) def blink_cursor_on(self): """Turns on the cursor, and makes it blink.""" self.hal_write_command(self.LCD_ON_CTRL | self.LCD_ON_DISPLAY | self.LCD_ON_CURSOR | self.LCD_ON_BLINK) def blink_cursor_off(self): """Turns on the cursor, and makes it no blink (i.e. be solid).""" self.hal_write_command(self.LCD_ON_CTRL | self.LCD_ON_DISPLAY | self.LCD_ON_CURSOR) def display_on(self): """Turns on (i.e. unblanks) the LCD.""" self.hal_write_command(self.LCD_ON_CTRL | self.LCD_ON_DISPLAY) def display_off(self): """Turns off (i.e. blanks) the LCD.""" self.hal_write_command(self.LCD_ON_CTRL) def backlight_on(self): """Turns the backlight on. This isn't really an LCD command, but some modules have backlight controls, so this allows the hal to pass through the command. """ self.backlight = True self.hal_backlight_on() def backlight_off(self): """Turns the backlight off. This isn't really an LCD command, but some modules have backlight controls, so this allows the hal to pass through the command. """ self.backlight = False self.hal_backlight_off() def move_to(self, cursor_x, cursor_y): """Moves the cursor position to the indicated position. The cursor position is zero based (i.e. cursor_x == 0 indicates first column). """ self.cursor_x = cursor_x self.cursor_y = cursor_y addr = cursor_x & 0x3f if cursor_y & 1: addr += 0x40 # Lines 1 & 3 add 0x40 if cursor_y & 2: addr += 0x14 # Lines 2 & 3 add 0x14 self.hal_write_command(self.LCD_DDRAM | addr) def putchar(self, char): """Writes the indicated character to the LCD at the current cursor position, and advances the cursor by one position. """ if char != '\n': self.hal_write_data(ord(char)) self.cursor_x += 1 if self.cursor_x >= self.num_columns or char == '\n': self.cursor_x = 0 self.cursor_y += 1 if self.cursor_y >= self.num_lines: self.cursor_y = 0 self.move_to(self.cursor_x, self.cursor_y) def putstr(self, string): """Write the indicated string to the LCD at the current cursor position and advances the cursor position appropriately. """ for char in string: self.putchar(char) def custom_char(self, location, charmap): """Write a character to one of the 8 CGRAM locations, available as chr(0) through chr(7). """ location &= 0x7 self.hal_write_command(self.LCD_CGRAM | (location << 3)) time.sleep_us(40) for i in range(8): self.hal_write_data(charmap[i]) time.sleep_us(40) self.move_to(self.cursor_x, self.cursor_y) def hal_backlight_on(self): """Allows the hal layer to turn the backlight on. If desired, a derived HAL class will implement this function. """ pass def hal_backlight_off(self): """Allows the hal layer to turn the backlight off. If desired, a derived HAL class will implement this function. """ pass def hal_write_command(self, cmd): """Write a command to the LCD. It is expected that a derived HAL class will implement this function. """ raise NotImplementedError def hal_write_data(self, data): """Write data to the LCD. It is expected that a derived HAL class will implement this function. """ raise NotImplementedError |
i2c_lcd.py
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from lcd_api import LcdApi from machine import I2C from time import sleep_ms # The PCF8574 has a jumper selectable address: 0x20 - 0x27 DEFAULT_I2C_ADDR = 0x27 # Defines shifts or masks for the various LCD line attached to the PCF8574 MASK_RS = 0x01 MASK_RW = 0x02 MASK_E = 0x04 SHIFT_BACKLIGHT = 3 SHIFT_DATA = 4 class I2cLcd(LcdApi): """Implements a HD44780 character LCD connected via PCF8574 on I2C.""" def __init__(self, i2c, i2c_addr, num_lines, num_columns): self.i2c = i2c self.i2c_addr = i2c_addr self.i2c.writeto(self.i2c_addr, bytearray([0])) sleep_ms(20) # Allow LCD time to powerup # Send reset 3 times self.hal_write_init_nibble(self.LCD_FUNCTION_RESET) sleep_ms(5) # need to delay at least 4.1 msec self.hal_write_init_nibble(self.LCD_FUNCTION_RESET) sleep_ms(1) self.hal_write_init_nibble(self.LCD_FUNCTION_RESET) sleep_ms(1) # Put LCD into 4 bit mode self.hal_write_init_nibble(self.LCD_FUNCTION) sleep_ms(1) LcdApi.__init__(self, num_lines, num_columns) cmd = self.LCD_FUNCTION if num_lines > 1: cmd |= self.LCD_FUNCTION_2LINES self.hal_write_command(cmd) def hal_write_init_nibble(self, nibble): """Writes an initialization nibble to the LCD. This particular function is only used during initialization. """ byte = ((nibble >> 4) & 0x0f) << SHIFT_DATA self.i2c.writeto(self.i2c_addr, bytearray([byte | MASK_E])) self.i2c.writeto(self.i2c_addr, bytearray([byte])) def hal_backlight_on(self): """Allows the hal layer to turn the backlight on.""" self.i2c.writeto(self.i2c_addr, bytearray([1 << SHIFT_BACKLIGHT])) def hal_backlight_off(self): """Allows the hal layer to turn the backlight off.""" self.i2c.writeto(self.i2c_addr, bytearray([0])) def hal_write_command(self, cmd): """Writes a command to the LCD. Data is latched on the falling edge of E. """ byte = ((self.backlight << SHIFT_BACKLIGHT) | (((cmd >> 4) & 0x0f) << SHIFT_DATA)) self.i2c.writeto(self.i2c_addr, bytearray([byte | MASK_E])) self.i2c.writeto(self.i2c_addr, bytearray([byte])) byte = ((self.backlight << SHIFT_BACKLIGHT) | ((cmd & 0x0f) << SHIFT_DATA)) self.i2c.writeto(self.i2c_addr, bytearray([byte | MASK_E])) self.i2c.writeto(self.i2c_addr, bytearray([byte])) if cmd <= 3: # The home and clear commands require a worst case delay of 4.1 msec sleep_ms(5) def hal_write_data(self, data): """Write data to the LCD.""" byte = (MASK_RS | (self.backlight << SHIFT_BACKLIGHT) | (((data >> 4) & 0x0f) << SHIFT_DATA)) self.i2c.writeto(self.i2c_addr, bytearray([byte | MASK_E])) self.i2c.writeto(self.i2c_addr, bytearray([byte])) byte = (MASK_RS | (self.backlight << SHIFT_BACKLIGHT) | ((data & 0x0f) << SHIFT_DATA)) self.i2c.writeto(self.i2c_addr, bytearray([byte | MASK_E])) self.i2c.writeto(self.i2c_addr, bytearray([byte])) |
main.py
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from i2c_lcd import I2cLcd from machine import I2C from machine import Pin import utime as time i2c = I2C(id=1,scl=Pin(27),sda=Pin(26),freq=100000) lcd = I2cLcd(i2c, 0x27, 2, 16) # LCD 16x2 lcd.putstr('DiY Projects Lab') |
Once, you run all these codes on the Raspberry Pi Pico board, the LCD will start displaying the ‘DiY Projects Lab‘ Message on Display.
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9 Comments
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In the main.py you have the name wrong. it is in your listing “from pico_i2c_lcd import I2cLcd” where is needs to be “from i2c_lcd import I2cLcd”.
But it looks to be a very useful bit of software Thanks
Alan McDermott-Roe
G8UJS