/**
 * @file    sketch.ino
 * @brief   ECE 315 Assignment 3 - Pico ADC + SPI Custom Chip Interface
 *
 * This program runs on a Raspberry Pi Pico in the Wokwi simulator
 * using the Arduino-Pico framework.
 *
 * It performs the following:
 *   1. Reads the built-in ADC on GPIO26 (A0) to sample an analogue
 *      voltage from a custom "noise-maker" chip once per second.
 *   2. Transmits the formatted reading over SPI to a custom
 *      "my-output-display" SPI peripheral chip.
 *   3. Prints the reading to the Pico's serial console.
 *
 * Hardware connections (defined in diagram.json):
 *   noise-maker OUT  -> GP26 (A0 / ADC0)
 *   my-output-display SCK  -> GP18 (SPI0 SCK)
 *   my-output-display SDI  -> GP19 (SPI0 TX / MOSI)
 *   my-output-display nCS  -> GP17 (active-low chip select)
 *
 * @author  Yousef Moussa ymoussa
 * @date    2026
 * @course  ECE 315
 */

#include <SPI.h>

/* ---------- Pin Definitions ---------- */
#define ADC_PIN         26      /* GPIO26 = A0, ADC input channel 0          */
#define PIN_SPI_CS      17      /* Manual chip-select -> GP17 (active low)   */

/* ---------- Constants ---------- */
#define ADC_MAX_VALUE   1023.0f /* Arduino analogRead returns 10-bit (0-1023)*/
#define ADC_REF_VOLTAGE 3.3f   /* ADC reference voltage in volts            */
#define SAMPLE_PERIOD_MS 1000  /* Sampling period in milliseconds (1 sec)   */
#define MSG_BUF_SIZE    64     /* Size of the SPI message buffer             */

/**
 * @brief   Transmit a string over SPI to the output-display chip.
 *
 * Asserts the chip-select line (active low), sends the data bytes
 * using SPI.transfer(), then deasserts chip-select.
 *
 * @param   data    Pointer to the null-terminated string to transmit.
 * @param   len     Number of bytes to transmit.
 */
static void spi_send_string(const char *data, size_t len) {
    digitalWrite(PIN_SPI_CS, LOW);
    for (size_t i = 0; i < len; i++) {
        SPI.transfer(data[i]);
    }
    digitalWrite(PIN_SPI_CS, HIGH);
}

/**
 * @brief   Arduino setup - runs once at startup.
 *
 * Initialises the serial console, ADC input pin, SPI master,
 * and chip-select GPIO.
 */
void setup() {
    Serial.begin(115200);
    delay(1000);
    Serial.println("ECE 315 Assignment 3 - ADC + SPI Demo Started");

    pinMode(ADC_PIN, INPUT);

    pinMode(PIN_SPI_CS, OUTPUT);
    digitalWrite(PIN_SPI_CS, HIGH);

    SPI.begin();
}

/**
 * @brief   Arduino loop - runs repeatedly.
 *
 * Samples the ADC once per second, converts the raw reading to a
 * voltage, prints it to the serial console, and sends the formatted
 * string over SPI to the output-display chip.
 */
void loop() {
    uint16_t raw_adc = analogRead(ADC_PIN);
    float voltage = (float)raw_adc * (ADC_REF_VOLTAGE / ADC_MAX_VALUE);

    char msg[MSG_BUF_SIZE];
    snprintf(msg, sizeof(msg), "ADC: raw=%u, voltage=%.4f V\n",
             raw_adc, voltage);

    Serial.printf("[Pico] %s", msg);

    spi_send_string(msg, strlen(msg));

    delay(SAMPLE_PERIOD_MS);
}