/**
 * ECE 315 Computer Interfacing
 * Assignment 3
 *
 * @file    main.c
 * @details Samples a pseudo-random analogue voltage from the `noise-maker`
 *          custom chip once per second using the Pico's built-in ADC (GPIO26 /
 *          ADC0). The 12-bit ADC result is formatted as a decimal string and
 *          transmitted byte-by-byte over SPI to the `my-output-display` custom
 *          chip, terminated with a newline so the display chip knows when to
 *          flush its buffer. The same value is also printed locally via
 *          printf() so that the Wokwi serial console shows progress.
 *
 *          Hardware connections
 *          --------------------
 *          noise-maker  OUT  --> GPIO26 (ADC0)
 *          my-output-display:
 *            SCK  --> GPIO18  (SPI0 SCK)
 *            SDI  --> GPIO19  (SPI0 TX / MOSI)
 *            nCS  --> GPIO17  (SPI0 CS, driven manually)
 *
 * @author  Komaldeep Taggar, CCID ktaggar
 * @date    2025
 * @copyright 2025, University of Alberta
 * @version 1.0
 * @licence MIT
 */

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

// Pin / peripheral configuration
#define ADC_PIN         26
#define ADC_CHANNEL     0
#define SPI_PORT        spi0
#define SPI_BAUDRATE    1000000

// GPIO numbers for the SPI bus
#define PIN_SCK         18
#define PIN_MOSI        19 
#define PIN_CS          17

// Sample period in milliseconds (1000 ms = 1 second)
#define SAMPLE_PERIOD_MS  1000

// The following function sends a null-terminated string via SPI
static void spi_send_string(const char *str) {
    gpio_put(PIN_CS, 0);

    size_t len = strlen(str);
    for (size_t i = 0; i < len; i++) {
        uint8_t byte = (uint8_t)str[i];
        spi_write_blocking(SPI_PORT, &byte, 1);
    }

    gpio_put(PIN_CS, 1);
}

int main(void) {
    stdio_init_all();

    // Setup the ADC
    adc_init();
    adc_gpio_init(ADC_PIN);          
    adc_select_input(ADC_CHANNEL);  

    // Setup SPI
    spi_init(SPI_PORT, SPI_BAUDRATE);

    // Assign SPI functions to GPIO pins
    gpio_set_function(PIN_SCK,  GPIO_FUNC_SPI);
    gpio_set_function(PIN_MOSI, GPIO_FUNC_SPI);

    // Chip-select is driven as a plain GPIO
    gpio_init(PIN_CS);
    gpio_set_dir(PIN_CS, GPIO_OUT);
    gpio_put(PIN_CS, 1);

    printf("ECE 315 Assignment 3 - noise sampler ready\n");

    // Main sampling loop
    while (true) {

        // Read 12-bit ADC value (0 – 4095)
        uint16_t raw = adc_read();
 
        /*
         * Convert to voltage. The Pico ADC reference is 3.3 V over 12 bits,
         * so each count = 3.3 / 4096 V. The noise-maker outputs 0–1 V,
         * which maps to the lower portion of that range.
         */
        float voltage = raw * (3.3f / 4096.0f);

        // Print to the serial monito
        printf("main.c  ADC raw=%-5u  voltage=%.4f V\n", raw, voltage);

        // Build the message string to forward to the display
        char msg[64];
        snprintf(msg, sizeof(msg), "ADC raw=%-5u  voltage=%.4f V\n", raw, voltage);

        // Send over SPI to my-output-display
        spi_send_string(msg);

        // Wait one second before the next sample
        sleep_ms(SAMPLE_PERIOD_MS);
    }

    return 0;
}