/**
 * @file    main.c
 * @brief   UART console, interrupt-driven 4×4 keypad input, and Morse LED blink on MSP430FR2355.
 *
 * Initializes peripheral modules and enters low-power mode, waking on keypress
 * interrupts to blink Morse code on LED and echo keys over UART.
 *
 * @date    2025-07-02
 */

#include <msp430.h>
#include <driverlib.h>
#include <stdint.h>
#include <stdio.h>
#include <stdbool.h>
#include "keypad.h"
#include "morse.h"

/** UART port/pin definitions */
#define UART_TX_PORT    GPIO_PORT_P1 /** UART TX port */
#define UART_TX_PIN     GPIO_PIN2    /** UART TX pin */
#define UART_RX_PORT    GPIO_PORT_P1 /** UART RX port */
#define UART_RX_PIN     GPIO_PIN3    /**< UART RX pin */

/** UART baudrate configuration for 9600 @ 1MHz SMCLK */
#define BAUDRATE_PRESCL  6U   /**< UCBR */
#define BAUDRATE_FIRSTM  8U   /**< UCBRF */
#define BAUDRATE_SECONDM 0U   /**< UCBRS */

/** On-board LED port and pin (used by Morse module) */
#define LED_PORT        GPIO_PORT_P1    /**< On-board LED port */
#define LED_PIN         GPIO_PIN0       /**< On-board LED pin */

/** Shared buffer for last key press and ready flag (set in ISR) */
volatile char  g_lastKey  = 0;      /**< Last key pressed */
volatile bool  g_keyReady = false;  /**< Flag indicating key available */

/**
 * @brief Initialize UART module for console output at 9600 baud.
 */
static void initSerial(void)
{
    EUSCI_A_UART_initParam uartCfg;
    
    /* Configure TX/RX pins for UART function */
    GPIO_setAsPeripheralModuleFunctionInputPin(
        UART_TX_PORT | UART_RX_PORT,
        UART_TX_PIN  | UART_RX_PIN,
        GPIO_PRIMARY_MODULE_FUNCTION
    );

    /* Populate UART configuration structure */
    uartCfg.selectClockSource    = EUSCI_A_UART_CLOCKSOURCE_SMCLK;
    uartCfg.clockPrescalar       = BAUDRATE_PRESCL;
    uartCfg.firstModReg          = BAUDRATE_FIRSTM;
    uartCfg.secondModReg         = BAUDRATE_SECONDM;
    uartCfg.parity               = EUSCI_A_UART_NO_PARITY;
    uartCfg.msborLsbFirst        = EUSCI_A_UART_LSB_FIRST;
    uartCfg.numberofStopBits     = EUSCI_A_UART_ONE_STOP_BIT;
    uartCfg.uartMode             = EUSCI_A_UART_MODE;
    uartCfg.overSampling         = EUSCI_A_UART_OVERSAMPLING_BAUDRATE_GENERATION;

    /* Apply configuration and enable UART */
    EUSCI_A_UART_init(EUSCI_A0_BASE, &uartCfg);
    EUSCI_A_UART_enable(EUSCI_A0_BASE);
}

/**
 * @brief Transmit a null-terminated string over UART.
 * @param s  Pointer to string to send
 */
static void serialPrint(const char *s)
{
    const char *ptr = s;
    while (*ptr) {
        /* Send next character */
        EUSCI_A_UART_transmitData(EUSCI_A0_BASE, *ptr++);
        /* Wait until transmission completes */
        while (EUSCI_A_UART_queryStatusFlags(
               EUSCI_A0_BASE, EUSCI_A_UART_BUSY));
    }
}

/**
 * @brief Keypad callback invoked on key press interrupt.
 * @param key  ASCII character of pressed key
 *
 * Stores key, sets ready flag, and blinks Morse code on LED.
 */
static void myKeyHandler(char key)
{
    g_lastKey  = key;
    g_keyReady = true;
    blinkMorseChar(key);
}

/**
 * @brief Main application entry point.
 *
 * Sets up GPIO, UART, keypad interrupts, and enters low-power loop.
 * On keypress, echoes key over UART.
 *
 * @return Never returns
 */
int main(void)
{
    char buf[32];
    int len;

    /* Stop watchdog and unlock GPIO pins */
    WDT_A_hold(WDT_A_BASE);
    PMM_unlockLPM5();

    /* Initialize on-board LED (used by Morse blinking) */
    GPIO_setAsOutputPin(LED_PORT, LED_PIN);
    GPIO_setOutputLowOnPin(LED_PORT, LED_PIN);

    /* Initialize UART console */
    initSerial();
    serialPrint("Keypad + LED test starting...\r\n");

    /* Initialize keypad interrupt driver */
    initKeypadInterrupts(myKeyHandler);

    /* Enter low-power mode and wait for key interrupts */
    for (;;) {
        __bis_SR_register(LPM0_bits | GIE);  /* Enter LPM0 with interrupts enabled */
        __no_operation();

        if (g_keyReady) {
            /* Echo key over UART */
            len = sprintf(buf, "Key pressed: %c\r\n", g_lastKey);
            (void)len;
            serialPrint(buf);
            g_keyReady = false;
        }
    }

    /* Should never reach here */
    return 0;
}