MSP432P401R 執行 timerled 範例時出錯

HI~各位

請問 當我執行simplelink_msp432_sdk_1_40_01_00 裡面的範例

C:\ti\simplelink_msp432_sdk_1_40_01_00\examples\rtos\MSP_EXP432P401R\drivers\timerled

當 timerCallback 只有執行  GPIO_toggle(Board_GPIO_LED0); 不會有錯誤。

但是當我將timerCallback內容修改為    UART_write(uart, echoPrompt, sizeof(echoPrompt)); 則會出現不正常錯誤

下面是我修改過的code

不知哪邊出了問題?

/*
 *  ======== timerled.c ========
 */

#include <stddef.h>

/* Driver Header files */
#include <ti/drivers/GPIO.h>
#include <ti/drivers/Timer.h>
#include <ti/drivers/UART.h>

/* Board Header file */
#include "Board.h"


/* Callback used for toggling the LED. */
void timerCallback(Timer_Handle myHandle);

/*
 *  ======== mainThread ========
 */

UART_Handle uart;
const char  echoPrompt[] = "Echoing characters:\r\n";

void *mainThread(void *arg0)
{


    UART_Params uartParams;

    /* Period and duty in microseconds */
    Timer_Handle timer0;
    Timer_Params params;

    /* Call driver init functions */
    GPIO_init();
    Timer_init();
    UART_init();
    /* Turn off user LED */
   // GPIO_write(Board_GPIO_LED0, Board_GPIO_LED_OFF);
    /* Create a UART with data processing off. */
     UART_Params_init(&uartParams);
     uartParams.writeDataMode = UART_DATA_BINARY;
     uartParams.readDataMode = UART_DATA_BINARY;
     uartParams.readReturnMode = UART_RETURN_FULL;
     uartParams.readEcho = UART_ECHO_OFF;
     uartParams.baudRate = 115200;

     uart = UART_open(Board_UART0, &uartParams);

    /* Setting up the timer in continuous callback mode that calls the callback
     * function every 1,000,000 microseconds, or 1 second.
     */
    Timer_Params_init(&params);
    params.period = 1000000;
    params.periodUnits = Timer_PERIOD_US;
    params.timerMode = Timer_CONTINUOUS_CALLBACK;
    params.timerCallback = timerCallback;


    timer0 = Timer_open(Board_TIMER0, &params);

    if (timer0 == NULL) {
        /* Failed to initialized timer */
        while (1);
    }

    if (Timer_start(timer0) == Timer_STATUS_ERROR) {
        /* Failed to start timer */
        while (1);
    }

    return (NULL);
}

/*
 * This callback is called every 1,000,000 microseconds, or 1 second. Because
 * the LED is toggled each time this function is called, the LED will blink at
 * a rate of once every 2 seconds.
 * */
void timerCallback(Timer_Handle myHandle)
{
    GPIO_toggle(Board_GPIO_LED0);
    UART_write(uart, echoPrompt, sizeof(echoPrompt));
}