/** * Copyright (c) 2020 Raspberry Pi (Trading) Ltd. * * SPDX-License-Identifier: BSD-3-Clause */ #include <stdio.h> #include <string.h> #include "pico/stdlib.h" #include "hardware/i2c.h" #include "pico/binary_info.h" /* Example code to drive a 16x2 LCD panel via a I2C bridge chip (e.g. PCF8574) NOTE: The panel must be capable of being driven at 3.3v NOT 5v. The Pico GPIO (and therefore I2C) cannot be used at 5v. You will need to use a level shifter on the I2C lines if you want to run the board at 5v. Connections on Raspberry Pi Pico board, other boards may vary. GPIO 4 (pin 6)-> SDA on LCD bridge board GPIO 5 (pin 7)-> SCL on LCD bridge board 3.3v (pin 36) -> VCC on LCD bridge board GND (pin 38) -> GND on LCD bridge board */ // commands const int LCD_CLEARDISPLAY = 0x01; const int LCD_RETURNHOME = 0x02; const int LCD_ENTRYMODESET = 0x04; const int LCD_DISPLAYCONTROL = 0x08; const int LCD_CURSORSHIFT = 0x10; const int LCD_FUNCTIONSET = 0x20; const int LCD_SETCGRAMADDR = 0x40; const int LCD_SETDDRAMADDR = 0x80; // flags for display entry mode const int LCD_ENTRYSHIFTINCREMENT = 0x01; const int LCD_ENTRYLEFT = 0x02; // flags for display and cursor control const int LCD_BLINKON = 0x01; const int LCD_CURSORON = 0x02; const int LCD_DISPLAYON = 0x04; // flags for display and cursor shift const int LCD_MOVERIGHT = 0x04; const int LCD_DISPLAYMOVE = 0x08; // flags for function set const int LCD_5x10DOTS = 0x04; const int LCD_2LINE = 0x08; const int LCD_8BITMODE = 0x10; // flag for backlight control const int LCD_BACKLIGHT = 0x08; const int LCD_ENABLE_BIT = 0x04; // By default these LCD display drivers are on bus address 0x27 static int addr = 0x27; // Modes for lcd_send_byte #define LCD_CHARACTER 1 #define LCD_COMMAND 0 #define MAX_LINES 2 #define MAX_CHARS 16 /* Quick helper function for single byte transfers */ void i2c_write_byte(uint8_t val) { #ifdef i2c_default i2c_write_blocking(i2c_default, addr, &val, 1, false); #endif } void lcd_toggle_enable(uint8_t val) { // Toggle enable pin on LCD display // We cannot do this too quickly or things don't work #define DELAY_US 600 sleep_us(DELAY_US); i2c_write_byte(val | LCD_ENABLE_BIT); sleep_us(DELAY_US); i2c_write_byte(val & ~LCD_ENABLE_BIT); sleep_us(DELAY_US); } // The display is sent a byte as two separate nibble transfers void lcd_send_byte(uint8_t val, int mode) { uint8_t high = mode | (val & 0xF0) | LCD_BACKLIGHT; uint8_t low = mode | ((val << 4) & 0xF0) | LCD_BACKLIGHT; i2c_write_byte(high); lcd_toggle_enable(high); i2c_write_byte(low); lcd_toggle_enable(low); } void lcd_clear(void) { lcd_send_byte(LCD_CLEARDISPLAY, LCD_COMMAND); } // go to location on LCD void lcd_set_cursor(int line, int position) { int val = (line == 0) ? 0x80 + position : 0xC0 + position; lcd_send_byte(val, LCD_COMMAND); } static inline void lcd_char(char val) { lcd_send_byte(val, LCD_CHARACTER); } void lcd_string(const char *s) { while (*s) { lcd_char(*s++); } } void lcd_init() { lcd_send_byte(0x03, LCD_COMMAND); lcd_send_byte(0x03, LCD_COMMAND); lcd_send_byte(0x03, LCD_COMMAND); lcd_send_byte(0x02, LCD_COMMAND); lcd_send_byte(LCD_ENTRYMODESET | LCD_ENTRYLEFT, LCD_COMMAND); lcd_send_byte(LCD_FUNCTIONSET | LCD_2LINE, LCD_COMMAND); lcd_send_byte(LCD_DISPLAYCONTROL | LCD_DISPLAYON, LCD_COMMAND); lcd_clear(); } int main() { #if !defined(i2c_default) || !defined(PICO_DEFAULT_I2C_SDA_PIN) || !defined(PICO_DEFAULT_I2C_SCL_PIN) #warning i2c/lcd_1602_i2c example requires a board with I2C pins #else // This example will use I2C0 on the default SDA and SCL pins (4, 5 on a Pico) i2c_init(i2c_default, 100 * 1000); gpio_set_function(PICO_DEFAULT_I2C_SDA_PIN, GPIO_FUNC_I2C); gpio_set_function(PICO_DEFAULT_I2C_SCL_PIN, GPIO_FUNC_I2C); gpio_pull_up(PICO_DEFAULT_I2C_SDA_PIN); gpio_pull_up(PICO_DEFAULT_I2C_SCL_PIN); // Make the I2C pins available to picotool bi_decl(bi_2pins_with_func(PICO_DEFAULT_I2C_SDA_PIN, PICO_DEFAULT_I2C_SCL_PIN, GPIO_FUNC_I2C)); lcd_init(); static char *message[] = { "RP2040 by", "Raspberry Pi", "A brand new", "microcontroller", "Twin core M0", "Full C SDK", "More power in", "your product", "More beans", "than Heinz!" }; while (1) { for (uint m = 0; m < sizeof(message) / sizeof(message[0]); m += MAX_LINES) { for (int line = 0; line < MAX_LINES; line++) { lcd_set_cursor(line, (MAX_CHARS / 2) - strlen(message[m + line]) / 2); lcd_string(message[m + line]); } sleep_ms(2000); lcd_clear(); } } #endif }

This firmware image was imported from the pico-examples repository. 


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