Embedded-Hacking/drivers/0x08_lcd1602_cbm/Src/main.c

/**
 * @file main.c
 * @brief LCD1602 demonstration: static title and live counter display.
 * @author Kevin Thomas
 * @date 2026
 *
 * Drives a 16x2 HD44780 LCD via a PCF8574 I2C backpack. Line 0
 * shows a static title ("Reverse Eng.") and line 1 displays a
 * counter that increments every second. The counter value is
 * also printed over UART for debugging.
 *
 * Wiring:
 *  GPIO0  -> UART TX (USB-to-UART adapter RX)
 *  GPIO1  -> UART RX (USB-to-UART adapter TX)
 *  GPIO2  -> PCF8574 backpack SDA (4.7 kohm pull-up to 3.3 V)
 *  GPIO3  -> PCF8574 backpack SCL (4.7 kohm pull-up to 3.3 V)
 *  3.3V   -> PCF8574 backpack VCC
 *  GND    -> PCF8574 backpack GND
 *
 * MIT License
 *
 * Copyright (c) 2026 Kevin Thomas
 *
 * Permission is hereby granted, free of charge, to any person obtaining a copy
 * of this software and associated documentation files (the "Software"), to deal
 * in the Software without restriction, including without limitation the rights
 * to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
 * copies of the Software, and to permit persons to whom the Software is
 * furnished to do so, subject to the following conditions:
 *
 * The above copyright notice and this permission notice shall be included in all
 * copies or substantial portions of the Software.
 *
 * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
 * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
 * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
 * AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
 * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
 * OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
 * SOFTWARE.
 */
#include "rp2350_i2c.h"
#include "rp2350_lcd1602.h"
#include "rp2350_uart.h"
#include "rp2350_xosc.h"
#include "rp2350_delay.h"

/** @brief Delay between LCD counter updates in milliseconds */
#define COUNT_DELAY_MS 1000

/**
  * @brief  Copy reversed digits from tmp into buf in correct order.
  * @param  tmp reversed digit buffer
  * @param  len number of digits
  * @param  buf output buffer
  * @retval None
  */
static void reverse_copy(const char *tmp, int len, char *buf)
{
  for (int j = 0; j < len; j++)
    buf[j] = tmp[len - 1 - j];
  buf[len] = '\0';
}

/**
  * @brief  Convert an unsigned 32-bit integer to a decimal string.
  *
  *         Writes at most 10 decimal digits plus a null terminator
  *         into the provided buffer. The buffer must be at least
  *         11 bytes.
  *
  * @param  val value to convert
  * @param  buf destination buffer (minimum 11 bytes)
  * @retval None
  */
static void uint_to_str(uint32_t val, char *buf)
{
  char tmp[11];
  int i = 0;
  if (val == 0) { buf[0] = '0'; buf[1] = '\0'; return; }
  while (val > 0) 
  {
    tmp[i++] = (char)('0' + (val % 10));
    val /= 10;
  }
  reverse_copy(tmp, i, buf);
}

/**
  * @brief  Copy a null-terminated string into buf at a given offset.
  * @param  dst destination buffer
  * @param  off starting offset in destination
  * @param  src source string
  * @retval int new offset past the copied characters
  */
static int copy_str(char *dst, int off, const char *src)
{
  while (*src)
    dst[off++] = *src++;
  return off;
}

/**
  * @brief  Format "Count: " followed by a right-justified counter value.
  *
  *         Writes the formatted string into a 17-byte buffer and pads
  *         with spaces to fill the 16-column display width.
  *
  * @param  count current counter value
  * @param  buf   destination buffer (minimum 17 bytes)
  * @retval None
  */
static void format_counter(uint32_t count, char *buf)
{
  char num[11];
  uint_to_str(count, num);
  int i = copy_str(buf, 0, "Count: ");
  i = copy_str(buf, i, num);
  while (i < 16) buf[i++] = ' ';
  buf[i] = '\0';
}

/**
  * @brief  Initialize clocks, I2C, LCD, UART, and display the static title.
  * @retval None
  */
static void lcd_setup(void)
{
  xosc_set_clk_ref();
  i2c_release_reset();
  i2c_init();
  lcd_init();
  uart_puts("LCD 1602 driver initialized at I2C addr 0x27\r\n");
  lcd_set_cursor(0, 0);
  lcd_puts("Reverse Eng.");
}

/**
  * @brief  Format, display, and print the current counter value.
  * @param  count current counter value
  * @retval None
  */
static void display_count(uint32_t count)
{
  char buf[17];
  format_counter(count, buf);
  lcd_set_cursor(1, 0);
  lcd_puts(buf);
  uart_puts(buf);
  uart_puts("\r\n");
}

int main(void)
{
  uint32_t count = 0;
  lcd_setup();
  while (1) 
  {
    display_count(count);
    count++;
    delay_ms(COUNT_DELAY_MS);
  }
}