rpi4b-temp-humidity/src/lcd.c

/*
 * lcd.c - Subroutines for communicating with HD44780U based LCD panels
 * Copyright (C) 2024  Alexander Rosenberg
 *
 * This program is free software: you can redistribute it and/or modify it under
 * the terms of the GNU General Public License as published by the Free Software
 * Foundation, either version 3 of the License, or (at your option) any later
 * version. See the LICENSE file for more information.
 *
 * This file was created with help from the document located here:
 * https://www.sparkfun.com/datasheets/LCD/HD44780.pdf
 */
#include "lcd.h"
#include "util.h"

#include <unistd.h>

static void lcd_set_read(LCD *lcd, bool is_read, bool force) {
    if (force || lcd->is_read != is_read) {
        gpio_config_t cfg = {.g_flags = is_read ? GPIO_PIN_INPUT
                                        : GPIO_PIN_OUTPUT};
        cfg.g_pin = lcd->d0;
        gpio_pin_set_flags(lcd->handle, &cfg);
        cfg.g_pin = lcd->d1;
        gpio_pin_set_flags(lcd->handle, &cfg);
        cfg.g_pin = lcd->d2;
        gpio_pin_set_flags(lcd->handle, &cfg);
        cfg.g_pin = lcd->d3;
        gpio_pin_set_flags(lcd->handle, &cfg);
        cfg.g_pin = lcd->d4;
        gpio_pin_set_flags(lcd->handle, &cfg);
        cfg.g_pin = lcd->d5;
        gpio_pin_set_flags(lcd->handle, &cfg);
        cfg.g_pin = lcd->d6;
        gpio_pin_set_flags(lcd->handle, &cfg);
        cfg.g_pin = lcd->d7;
        gpio_pin_set_flags(lcd->handle, &cfg);
        lcd->is_read = is_read;
    }
}

static void lcd_pulse_enable(LCD *lcd) {
    gpio_pin_high(lcd->handle, lcd->en);
    usleep(1); // min of 1000ns
    gpio_pin_low(lcd->handle, lcd->en);
}

LCD *lcd_open(gpio_handle_t handle, gpio_pin_t rs, gpio_pin_t rw, gpio_pin_t en,
              gpio_pin_t d0, gpio_pin_t d1, gpio_pin_t d2, gpio_pin_t d3,
              gpio_pin_t d4, gpio_pin_t d5, gpio_pin_t d6, gpio_pin_t d7) {
    LCD *lcd = malloc_checked(sizeof(LCD));
    lcd->handle = handle;
    lcd->rs = rs;
    lcd->rw = rw;
    lcd->en = en;
    lcd->d0 = d0;
    lcd->d1 = d1;
    lcd->d2 = d2;
    lcd->d3 = d3;
    lcd->d4 = d4;
    lcd->d5 = d5;
    lcd->d6 = d6;
    lcd->d7 = d7;
    gpio_pin_output(lcd->handle, lcd->rw);
    gpio_pin_output(lcd->handle, lcd->en);
    gpio_pin_output(lcd->handle, lcd->rs);
    lcd_clear(lcd);
    lcd_call(lcd, 0, 0, 0, 0, 1, 1, 1, 0, 0); // 5x8 font, 2 lines, 8bit
    lcd_entry_mode(lcd, LCD_INCREMENT, LCD_CURSOR_MOVE);
    lcd_display_control(lcd, LCD_CURSOR_NO_BLINK, LCD_CURSOR_OFF, LCD_DISPLAY_ON);
    LOG_VERBOSE("Initializing LCD: rs=%d, rw=%d, en=%d, d={%d, %d, %d, %d, %d, "
                "%d, %d, %d}\n", rs, rw, en, d0, d1, d2, d3, d4, d5, d6, d7);
    return lcd;
}

void lcd_close(LCD *lcd) {
    LOG_VERBOSE("Closing LCD\n");
    free(lcd);
}

void lcd_call(LCD *lcd, gpio_value_t rs, gpio_value_t d0, gpio_value_t d1,
              gpio_value_t d2, gpio_value_t d3, gpio_value_t d4,
              gpio_value_t d5, gpio_value_t d6, gpio_value_t d7) {
    while(lcd_is_busy(lcd)) {
        usleep(5);
    }
    lcd_set_read(lcd, false, false);
    gpio_pin_low(lcd->handle, lcd->en);
    gpio_pin_low(lcd->handle, lcd->rw);
    gpio_pin_set(lcd->handle, lcd->rs, rs);
    gpio_pin_set(lcd->handle, lcd->d0, d0);
    gpio_pin_set(lcd->handle, lcd->d1, d1);
    gpio_pin_set(lcd->handle, lcd->d2, d2);
    gpio_pin_set(lcd->handle, lcd->d3, d3);
    gpio_pin_set(lcd->handle, lcd->d4, d4);
    gpio_pin_set(lcd->handle, lcd->d5, d5);
    gpio_pin_set(lcd->handle, lcd->d6, d6);
    gpio_pin_set(lcd->handle, lcd->d7, d7);
    lcd_pulse_enable(lcd);
}

void lcd_write_char(LCD *lcd, char c) {
    lcd_call(lcd, 1, c & 1, (c >> 1) & 1, (c >> 2) & 1, (c >> 3) & 1, (c >> 4) & 1,
             (c >> 5) & 1, (c >> 6) & 1, (c >> 7) & 1);
}

size_t lcd_write_string(LCD *lcd, const char *str) {
    size_t count;
    for (count = 0; *str; ++str, ++count) {
        lcd_write_char(lcd, *str);
    }
    return count;
}

void lcd_move_to(LCD *lcd, gpio_value_t line, gpio_value_t col) {
    lcd_call(lcd, 0, col & 1, (col >> 1) & 1, (col >> 2) & 1,
             (col >> 3) & 1, (col >> 4) & 1, (col >> 5) & 1, line, 1);
}

void lcd_clear(LCD *lcd) {
    lcd_call(lcd, 0, 1, 0, 0, 0, 0, 0, 0, 0);
}

void lcd_display_control(LCD *lcd, gpio_value_t b, gpio_value_t c, gpio_value_t d) {
    lcd_call(lcd, 0, b, c, d, 1, 0, 0, 0, 0);
}

void lcd_entry_mode(LCD *lcd, gpio_value_t id, gpio_value_t s) {
    lcd_call(lcd, 0, s, id, 1, 0, 0, 0, 0, 0);
}

void lcd_cursor_shift(LCD *lcd, gpio_value_t sc, gpio_value_t rl) {
    lcd_call(lcd, 0, 0, 0, rl, sc, 1, 0, 0, 0);
}

bool lcd_is_busy(LCD *lcd) {
    lcd_set_read(lcd, true, false);
    gpio_pin_low(lcd->handle, lcd->rs);
    gpio_pin_high(lcd->handle, lcd->rw);
    gpio_pin_high(lcd->handle, lcd->en);
    usleep(1);
    gpio_value_t busy = gpio_pin_get(lcd->handle, lcd->d7);
    gpio_pin_low(lcd->handle, lcd->en);
    usleep(1);
    return busy;
    
}