/**
 * @file main.c
 * @author Amar Kulovac
 * @copyright SPDX-License-Identifier: MIT
 * @brief Main module for the Raspberry Pi Pico noise-maker interface.
 * This module interfaces with a noise-maker chip via ADC and reports the
 * calculated voltage. It also outputs string data to an SPI display chip,
 * using newline characters as delimiters.
 */

#include "hardware/adc.h"
#include "hardware/spi.h"
#include "pico/stdlib.h"
#include <stdio.h>
#include <string.h>

/** @name ADC Configuration */
/**@{*/
#define ADC_PIN 28 /**< GPIO pin used for ADC input */
#define ADC_PORT 2 /**< ADC MUX input index corresponding to GPIO 28 */
/**@}*/

/** @name SPI Configuration */
/**@{*/
#define TFT_SPI spi0     /**< Hardware SPI instance used for the display */
#define CS_PIN 27        /**< Chip Select (nCS) GPIO pin */
#define SCK_PIN 18       /**< SPI Serial Clock GPIO pin */
#define MOSI_PIN 19      /**< SPI Main-Out-Sub-In GPIO pin */
#define SCK_FREQ 1000000 /**< SPI Clock Frequency (1MHz) */
/**@}*/

/** @brief Main loop delay in milliseconds */
#define SLEEP 1000

/**
 * @brief ADC scaling factor.
 * @note Testing indicates the Wokwi simulation environment uses a 5.0V
 * reference for its analog engine, resulting in values bounded between 0 and 1.
 * On physical hardware, this would typically be 3.3f.
 */
const float conversion_factor = 5.0f / ((1 << 12) - 1);

/**
 * @brief Converts raw ADC integer values to a floating-point voltage.
 * @param raw The 12-bit digital value read from the ADC (0-4095).
 * @return float The calculated voltage based on the conversion_factor.
 */
float raw_to_voltage(uint16_t raw) { return (float)raw * conversion_factor; }

/**
 * @brief Application entry point.
 * * Initializes standard I/O, configures the ADC for noise-maker input,
 * and sets up the SPI peripheral for the TFT display. The main loop
 * continuously reads the ADC and transmits the formatted string via SPI.
 */
int main() {
  stdio_init_all();

  /* ADC Initialization */
  adc_init();
  adc_gpio_init(ADC_PIN);
  adc_select_input(ADC_PORT);

  /* SPI Initialization */
  spi_init(TFT_SPI, SCK_FREQ);
  gpio_set_function(SCK_PIN, GPIO_FUNC_SPI);
  gpio_set_function(MOSI_PIN, GPIO_FUNC_SPI);

  /* Chip Select (nCS) Setup */
  gpio_init(CS_PIN);
  gpio_set_dir(CS_PIN, GPIO_OUT);
  gpio_put(CS_PIN, 1);

  printf("pico initialized\n");

  while (true) {
    uint16_t raw_value = adc_read();
    float voltage = raw_to_voltage(raw_value);

    printf("Raw: %d, Voltage: %f V\n", raw_value, voltage);

    char buffer[16];
    snprintf(buffer, sizeof(buffer), "%.3f", voltage);

    /* Assert nCS Low to start communication */
    gpio_put(CS_PIN, 0);
    spi_write_blocking(TFT_SPI, "Voltage: ", 9);
    spi_write_blocking(TFT_SPI, buffer, strlen(buffer));
    spi_write_blocking(TFT_SPI, "V\n", 2);
    /* Assert nCS High to end communication */
    gpio_put(CS_PIN, 1);

    /* Data sent while CS is High will be ignored by the peripheral */
    spi_write_blocking(TFT_SPI, "wont appear\n", 12);

    sleep_ms(SLEEP);
  }
}