CCS/MSP-EXP432P401R: Busfault when calling `Display_printf` in interrupt callback in TIRTOS application

Part Number: MSP-EXP432P401R
Other Parts Discussed in Thread: SYSBIOS

Tool/software: Code Composer Studio

Hello everyone

I am writing an application for the MSP432 development board using TIRTOS. The structure of the application skeleton is the following (see also code below):

• There are two GPIO interrupts set up for two buttons. When a button is pressed, the associated interrupt handler sends a message over the UART to the connected PC using the `Display_printf` library function.
• In addition there is a timer set up which causes periodic interrupts every 1ms.

If I run the application and click the buttons sequentially a few times, the system always freezes in an exception handler. The decoded exception says `Hard Fault: FORCED: BUSFAULT: PRECISERR.Data Access Error. Address = 0x40000c04` and the exception call stack says `ti_sysbios_knl_Task_unblockI__E`. 

I'm not quite sure why this error occurs. Is there anything I need to consider or I'm not aware of when I want to call `Display_printf`?

The application code:

/* POSIX Header files */
#include <pthread.h>

/* Driver Header files */
#include <ti/drivers/ADC.h>
#include <ti/display/Display.h>
#include <ti/drivers/PWM.h>
#include <ti/drivers/Timer.h>
#include <ti/drivers/GPIO.h>

/* Driver configuration */
#include "ti_drivers_config.h"
#include "coil_control.h"


/* State machine related variables */
enum driver_state state = INIT;

/* current timer value */
/* Open the timer */
Timer_Handle timer0;
Timer_Params t_params;

uint32_t counter_value=0;

static Display_Handle display;

/*
 *  ======== controller / duty cycle thread ========
 *  measure the voltage produced by current sensor amplifier
 */
void current_controller(Timer_Handle myHandle){
    //counter_value+=1;
}

/*
 *  ======== sw1 callback ========
 *  advance state machine forward
 */
void sw1_callback(uint_least8_t ind){
    counter_value+=1;
    Display_printf(display, 0, 0, "SW1 pressed\n");
}

/*
 *  ======== cw2 callback ========
 *  advance state machine backwards
 */
void sw2_callback(uint_least8_t ind){
    counter_value+=1;
    Display_printf(display, 0, 0, "SW2 pressed\n");
}

/*
 *  ======== mainThread ========
 *  the main thread sets up a timer for
 *  - periodic currentsens_voltage_measurement (current sens thread)
 *  - periodic adjustment of duty cycle (current control thread)
 *  - periodic communication with PC (communication thread)
 */
 void *mainThread(void *arg0)
{
    //------------------------------------------------
    // GPIO 0 Setup
    //------------------------------------------------
    GPIO_setConfig(CONFIG_GPIO_S1, GPIO_CFG_IN_PU | GPIO_CFG_IN_INT_FALLING);
    GPIO_setConfig(CONFIG_GPIO_S2, GPIO_CFG_IN_PU | GPIO_CFG_IN_INT_FALLING);
    GPIO_setCallback(CONFIG_GPIO_S1, sw1_callback);
    GPIO_setCallback(CONFIG_GPIO_S2, sw2_callback);
    GPIO_enableInt(CONFIG_GPIO_S1);
    GPIO_enableInt(CONFIG_GPIO_S2);

    //------------------------------------------------
    // Timer 32 Setup
    //------------------------------------------------
    Timer_init();
    Timer_Params_init(&t_params);
    t_params.period = 1000;
    t_params.periodUnits = Timer_PERIOD_US;
    t_params.timerMode = Timer_CONTINUOUS_CALLBACK;
    t_params.timerCallback = current_controller;
    timer0 = Timer_open(CONFIG_TIMER_0, &t_params);
    if (timer0 == NULL) {
        /* Failed to initialized timer */
        while (1) {}
    }
    if (Timer_start(timer0) == Timer_STATUS_ERROR) {
        /* Failed to start timer */
        while (1) {}
    }

    /* Open the display for output */
    display = Display_open(Display_Type_UART, NULL);
    if (display == NULL) {
        /* Failed to open display driver */
        while (1);
    }

    Display_printf(display, 0, 0, "Starting the acdcsinglechannel example\n");

    return (NULL);
}