/* UART0-UART1 pass-through for ESP8266 Console
 *
 * ESP8266 socket header is connected to UART1.
 * Pin 2 - Tx (P3.3)
 * Pin 3 - Rx (P3.2)
 * UART0 is connected to the virtual COM port.
 * Both UART0 and UART2 are configured for 115200 Baud 8-N-1.
 * Use a terminal emulator to talk to UART0 through the virtual COM port.
 * If everything works out, type "AT<cr>" at the terminal emulator
 * should get "OK" back from ESP8266.
 *
 * The ESP8266 module must have the "AT" firmware. ESP8266 may have
 * different Baud rate than 115200 used in this program. 
 *
 * 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 UART0init(void);
void UART0Tx(char c);
unsigned char UART0Rx(void);
void delayMs(int n);

int main(void) {
    char c;
    
    UART2init();
    UART0init();
    delayMs(1);             /* wait for output line to stabilize */

    UART0Tx('>');           /* send prompt */
    
    for(;;) {
        c = UART0Rx();
        if (c != 0)
            UART2Tx(c); 

        c = UART2Rx();
        if (c != 0)
            UART0Tx(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;           /* P3.3, P3.2 for UART2 */
    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;
    
    if ((EUSCI_A2->IFG & 0x01) == 0)    /* if Rx buffer is empty */
        return 0;
    c = EUSCI_A2->RXBUF;                /* read the receive char */
    return c;
}

void UART0init(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;         /* 3000000 / 115200 = 26 */
    P1->SEL0 |= 0x0C;           /* P1.3, P1.2 for UART0 */
    P1->SEL1 &= ~0x0C;
    EUSCI_A0->CTLW0 &= ~1;      /* take UART out of reset mode */
}

void UART0Tx(char c) {
    while(!(EUSCI_A0->IFG & 0x02)) { }  /* wait for transmit buffer empty */
    EUSCI_A0->TXBUF = c;                /* send a char */
}

unsigned char UART0Rx(void){
    char c;
    
    if ((EUSCI_A0->IFG & 0x01) == 0)    /* if Rx buffer is empty */
        return 0;
    c = EUSCI_A0->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 */
}