/* www.MicroDigitalEd.com
 * p4_1.c UART0 transmit
 *
 * Sending string "YES" to UART0 on MSP432 LaunchPad. 
 * The UART0 is connected to XDS110 on the LaunchPad and it has
 * a virtual connection to the host PC COM port.
 * Use TeraTerm to see the message "YES" on a PC.
 *
 * By default the subsystem master clock is 3 MHz.
 * Setting EUSCI_A0->BRW=26 with oversampling disabled yields 115200 Baud.
 *
 * Tested with Keil 5.20 and MSP432 Device Family Pack V2.2.0.
 */

#include "msp.h"

void UART0_init(void);
void delayMs(int n);

int main(void) {
    UART0_init();
    while (1) {
        while(!(EUSCI_A0->IFG & 0x02)) { }  /* wait for transmit buffer empty */
        EUSCI_A0->TXBUF = 'Y';              /* send a char */
        while(!(EUSCI_A0->IFG & 0x02)) { }
        EUSCI_A0->TXBUF = 'e';              /* send a char */
        while(!(EUSCI_A0->IFG & 0x02)) { }
        EUSCI_A0->TXBUF = 's';              /* send a char */
        delayMs(2);                         /* leave a gap between messages */
    }
}

void UART0_init(void)
{
    EUSCI_A0->CTLW0 |= 1;       /* put in reset mode for config */
    EUSCI_A0->MCTLW = 0;        /* disable oversampling */
    EUSCI_A0->CTLW0 = 0x0081;   /* 1 stop bit, no parity, SMCLK, 8-bit data */
    EUSCI_A0->BRW = 26;         /* 3,000,000 / 115200 = 26 */
    P1->SEL0 |= 0x0C;           /* P1.3, P1.2 for UART */
    P1->SEL1 &= ~0x0C;
    EUSCI_A0->CTLW0 &= ~1;      /* take UART out of reset mode */
}

/* delay milliseconds when system clock is at 3 MHz */
void delayMs(int n) {
    int i, j;
    
    for (j = 0; j < n; j++)
        for (i = 250; i > 0; i--);      /* Delay */
}