/* UART2 echo
 *
 * Pin header J34 is connected to UART2.
 * Pin 2 - Tx (P3.3)
 * Pin 3 - Rx (P3.2)
 * The UART2 is configure for 115200 Baud 8-N-1.
 * Connect a USB to 3.3V serial converter to a PC and launch a
 * terminal emulator on the PC. The keyboard input will be sent
 * by the terminal emulator to USB-serial converter. Connect the
 * Tx pin of the converter to the Rx (pin 3 of J34). This program
 * echoes back the characters to the Tx (pin 2 of J34). Connect Tx
 * of J34 to Rx of the USB-Serial converter and the character will
 * appear on the terminal emulator window.
 *
 * Built and tested with MSP432P401R Rev. C, Keil MDK-ARM v5.24a and MSP432P4xx_DFP v3.1.0
 */

#include "msp.h"

void UART2init(void);
void UART2Tx(char c);
unsigned char UART2Rx(void);
void delayMs(int n);

int main(void) {
    char c;
    
    UART2init();
    delayMs(1);             /* wait for output line to stabilize */

    UART2Tx('>');           /* send prompt */
    
    for(;;) {
        c = UART2Rx();
        if (c == '\r')
            UART2Tx('\n'); 
        UART2Tx(c); 
    }
}

void UART2init(void) {
    EUSCI_A2->CTLW0 |= 1;       /* put in reset mode for config */
    EUSCI_A2->MCTLW = 0;        /* disable oversampling */
    EUSCI_A2->CTLW0 = 0x0081;   /* 1 stop bit, no parity, SMCLK, 8-bit data */
    EUSCI_A2->BRW = 26;         /* 3000000 / 115200 = 26 */
    P3->SEL0 |= 0x0C;           /* P1.3, P1.2 for UART */
    P3->SEL1 &= ~0x0C;
    EUSCI_A2->CTLW0 &= ~1;      /* take UART out of reset mode */
}

void UART2Tx(char c) {
    while(!(EUSCI_A2->IFG & 0x02)) { }  /* wait for transmit buffer empty */
    EUSCI_A2->TXBUF = c;                /* send a char */
}

unsigned char UART2Rx(void){
    char c;
    
    while(!(EUSCI_A2->IFG & 0x01)) { }    /* wait until receive buffer is full */
    c = EUSCI_A2->RXBUF;                  /* read the receive char */
    return c;
}

/* system clock at 3 MHz */
void delayMs(int n) {
    int i, j;

    for (j = 0; j < n; j++)
        for (i = 750; i > 0; i--);      /* Delay */
}