Raspberry Pi Pico internal temperature sensor with LCD 16x2 example.

lcd_1602_temp.c

/**
 * 
 * Raspberry Pi Pico internal temperature sensor with LCD 16x2 example.
 * 
 * Copyright (c) 2020 Raspberry Pi (Trading) Ltd.
 *
 * Adapted by MaxMacSTN
 * 
 * SPDX-License-Identifier: BSD-3-Clause
 */

#include <stdio.h>
#include <string.h>
#include "pico/stdlib.h"
#include "hardware/i2c.h"
#include "hardware/gpio.h"
#include "hardware/adc.h"
#include "pico/binary_info.h"
#include <math.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 therefor 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;

#define I2C_PORT i2c0
// 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

const uint LED_PIN = PICO_DEFAULT_LED_PIN;
const uint DHT_PIN = 15;
const uint MAX_TIMINGS = 85;

/* Quick helper function for single byte transfers */
void i2c_write_byte(uint8_t val) {
    i2c_write_blocking(I2C_PORT, addr, &val, 1, false);
}

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 void inline 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() {

    stdio_init_all();
    adc_init();
    // Select ADC input 0 (GPIO26)
    gpio_set_dir(LED_PIN, GPIO_OUT);

    // This example will use I2C0 on GPIO4 (SDA) and GPIO5 (SCL)
    i2c_init(I2C_PORT, 100 * 1000);
    gpio_set_function(4, GPIO_FUNC_I2C);
    gpio_set_function(5, GPIO_FUNC_I2C);
    gpio_pull_up(4);
    gpio_pull_up(5);
    // Make the I2C pins available to picotool
    bi_decl( bi_2pins_with_func(4, 5, GPIO_FUNC_I2C));

    lcd_init();


    while (1) {

        const float conversion_factor = 3.3f / (1 << 12);
        adc_select_input(4);
        uint16_t result = adc_read();
        printf("Raw value: 0x%03x, voltage: %f V\n", result, result * conversion_factor);
        float reading = result * conversion_factor;
        float tempF = 27 - (reading - 0.706)/0.001721;
        float tempC = (tempF - 32) * 5/9;
        char *message[16]; 
        lcd_set_cursor(0, 0);
        lcd_string("  - RPi Pico -  ");
        lcd_set_cursor(1, 0);
        sprintf(message, "  Temp: %.1fc  ",tempC);
        lcd_string(message);
        sleep_ms(2000);
    }



    return 0;
}