#include <stdint.h>
#include <msp430.h>

#define interrupt(x) void __attribute__((interrupt (x)))

uint8_t rxbyte;
uint16_t rxbuf; // byte currently being received
uint8_t rxbit; // current bit
uint8_t rxdone; // done receiving byte

void delay_ms(uint16_t ms) {
    while (ms--)
        __delay_cycles(1000);
}

void wait_for_button() {
    while (!(P1IN & 0x08)) ;
    delay_ms(20);
    while (P1IN & 0x08) ;
    delay_ms(20);
}

uint16_t add = 0;

uint8_t debug[8];
uint8_t buf[32];
uint16_t bufp = 0;

int main() {
    WDTCTL = WDTPW | WDTHOLD;

    BCSCTL1 = CALBC1_1MHZ;
    DCOCTL = CALDCO_1MHZ;

    __delay_cycles(16000);

    // Button
    P1REN |= 0x08;
    P1OUT |= 0x08;

    // Led
    P1DIR |= 0x01;

    UCA0CTL1 |= UCSSEL_2; // SMCLK clock

    // http://mspgcc.sourceforge.net/cgi-bin/msp-uart.pl?clock=1000000&baud=9600&submit=calculate
    //UCA0BR0 = 0x68;
    //UCA0BR1 = 0x00;
    //UCA0MCTL = 0x04;

    // http://mspgcc.sourceforge.net/cgi-bin/msp-uart.pl?clock=8000000&baud=57600&submit=calculate
    UCA0BR0 = 0x8A;
    UCA0BR1 = 0x00;
    UCA0MCTL = 0xEF;

    // UART
    P1SEL |= 0x02 | 0x04;
    P1SEL2 |= 0x02 | 0x04; // RXD on P1.1, TXD on P1.2

    UCA0CTL1 &= ~UCSWRST; // Start UART

    IE2 |= UCA0RXIE;

    __enable_interrupt();

    while (1) {
        wait_for_button();
        P1OUT ^= 0x01;
        add++;
    }

    return 0;
}

interrupt(USCIAB0RX_VECTOR) uart_rx_isr() { 
    debug[0]++;
    while (!(IFG2 & UCA0TXIFG)) ;

    uint8_t rec = UCA0RXBUF;

    buf[bufp] = rec;
    bufp = (bufp + 1) % 32;

    UCA0TXBUF = rec + add;
}