CCS/TM4C1294NCPDT: GPIOPinWrite() with global vs local variables

Hello Engiz

When the Bus Fault occurs, what is the content of the NVIC_VAULT_STAT and NVIC_FAULT_ADDR registers?

Thanks Amit,

The registers are as follows (when the debugger is in FaultISR):

NVIC_FAULT_STAT: 0x00000000

NVIC_FAULT_ADDR: 0xE000EDF8

Hello Engiz,

If the FAULT Status register does not show any bit set then it means that there is no Bus Fault being generated. Could you please snapshot your CCS project and/or attach the same?

Another thing is the use of the API to configure the SSI controller is not correct

SSIConfigSetExpClk(SSI2_BASE, ui32SysClkFreq/100, SSI_FRF_MOTO_MODE_0,
SSI_MODE_MASTER, 10000, 8);

Must be

SSIConfigSetExpClk(SSI2_BASE, ui32SysClkFreq, SSI_FRF_MOTO_MODE_0,
SSI_MODE_MASTER, 10000, 8);

Hi Amit,

I misread the API manual, and thought that uiSSIClk was the SPI clock's frequency, and dividing ui32SysClkFreq by 100 would give me 1.2 MHz SPI clock frequency.

Anyway, I changed the initialization of the dummy variable from being a pointer to a variable, and the code works fine.

This is the fixed code:

#include <stdint.h>
#include <stdbool.h>
#include "inc/hw_memmap.h"
#include "inc/hw_ssi.h"
#include "inc/hw_types.h"
#include "driverlib/ssi.h"
#include "driverlib/gpio.h"
#include "driverlib/pin_map.h"
#include "driverlib/sysctl.h"
#include "driverlib/uart.h"
#include "utils/uartstdio.h"

uint32_t ui32SysClkFreq;


int main(void) {


	uint8_t cs_pins;
    uint32_t accel_data = 0, gyro_data = 0;
    uint32_t dummy = 0;

    cs_pins  =  GPIO_PIN_2 | GPIO_PIN_3;

    ui32SysClkFreq = SysCtlClockFreqSet((SYSCTL_XTAL_25MHZ |
    SYSCTL_OSC_MAIN | SYSCTL_USE_PLL | SYSCTL_CFG_VCO_480),
    120000000);


    SysCtlPeripheralEnable(SYSCTL_PERIPH_GPIOB);
    SysCtlPeripheralEnable(SYSCTL_PERIPH_GPIOD);
    SysCtlPeripheralEnable(SYSCTL_PERIPH_SSI2);


    GPIOPinConfigure(GPIO_PD3_SSI2CLK);
    GPIOPinConfigure(GPIO_PD0_SSI2XDAT1);
    GPIOPinConfigure(GPIO_PD1_SSI2XDAT0);
    GPIOPinTypeSSI(GPIO_PORTD_BASE,
                    GPIO_PIN_0|GPIO_PIN_1|GPIO_PIN_3);

    GPIOPinTypeGPIOOutput(GPIO_PORTB_BASE, GPIO_PIN_2 | GPIO_PIN_3);



    SSIConfigSetExpClk(SSI2_BASE, ui32SysClkFreq, SSI_FRF_MOTO_MODE_0,
                                                        SSI_MODE_MASTER, 10000, 8);

    SSIEnable(SSI2_BASE);
    // SSIAdvModeSet(SSI2_BASE,SSI_ADV_MODE_LEGACY);

    while(1)
    {


        GPIOPinWrite(GPIO_PORTB_BASE, cs_pins, GPIO_PIN_2 + GPIO_PIN_3);

        GPIOPinWrite(GPIO_PORTB_BASE, cs_pins, GPIO_PIN_3);

        SSIDataPut(SSI2_BASE, 0b10001111);
        while(SSIBusy(SSI2_BASE));
        SSIDataGet(SSI2_BASE, &dummy);   //dummy thing to clear FIFO
        while(SSIBusy(SSI2_BASE));
        SSIDataPut(SSI2_BASE, 0b0); //dummy thing to clear FIFO
        while(SSIBusy(SSI2_BASE));
        SSIDataGet(SSI2_BASE, &accel_data);
        while(SSIBusy(SSI2_BASE));

        GPIOPinWrite(GPIO_PORTB_BASE, cs_pins, GPIO_PIN_2);

        SSIDataPut(SSI2_BASE, 0b10001111);
        while(SSIBusy(SSI2_BASE));
        SSIDataGet(SSI2_BASE, &dummy);   //dummy thing to clear FIFO
        while(SSIBusy(SSI2_BASE));
        SSIDataPut(SSI2_BASE, 0b0); //dummy thing to clear FIFO
        while(SSIBusy(SSI2_BASE));
        SSIDataGet(SSI2_BASE, &gyro_data);
        while(SSIBusy(SSI2_BASE));

        GPIOPinWrite(GPIO_PORTB_BASE, cs_pins, GPIO_PIN_2 + GPIO_PIN_3);

        SysCtlDelay(SysCtlClockGet()/3);

    }
    return 0;
}

Whereas this one is the faulty:

#include <stdint.h>
#include <stdbool.h>
#include "inc/hw_memmap.h"
#include "inc/hw_ssi.h"
#include "inc/hw_types.h"
#include "driverlib/ssi.h"
#include "driverlib/gpio.h"
#include "driverlib/pin_map.h"
#include "driverlib/sysctl.h"
#include "driverlib/uart.h"
#include "utils/uartstdio.h"

uint32_t ui32SysClkFreq;


int main(void) {


	uint8_t cs_pins;
    uint32_t accel_data = 0, gyro_data = 0;
    uint32_t *dummy;

    cs_pins  =  GPIO_PIN_2 | GPIO_PIN_3;

    ui32SysClkFreq = SysCtlClockFreqSet((SYSCTL_XTAL_25MHZ |
    SYSCTL_OSC_MAIN | SYSCTL_USE_PLL | SYSCTL_CFG_VCO_480),
    120000000);


    SysCtlPeripheralEnable(SYSCTL_PERIPH_GPIOB);
    SysCtlPeripheralEnable(SYSCTL_PERIPH_GPIOD);
    SysCtlPeripheralEnable(SYSCTL_PERIPH_SSI2);


    GPIOPinConfigure(GPIO_PD3_SSI2CLK);
    GPIOPinConfigure(GPIO_PD0_SSI2XDAT1);
    GPIOPinConfigure(GPIO_PD1_SSI2XDAT0);
    GPIOPinTypeSSI(GPIO_PORTD_BASE,
                    GPIO_PIN_0|GPIO_PIN_1|GPIO_PIN_3);

    GPIOPinTypeGPIOOutput(GPIO_PORTB_BASE, GPIO_PIN_2 | GPIO_PIN_3);



    SSIConfigSetExpClk(SSI2_BASE, ui32SysClkFreq, SSI_FRF_MOTO_MODE_0,
                                                        SSI_MODE_MASTER, 10000, 8);

    SSIEnable(SSI2_BASE);
    // SSIAdvModeSet(SSI2_BASE,SSI_ADV_MODE_LEGACY);

    while(1)
    {


        GPIOPinWrite(GPIO_PORTB_BASE, cs_pins, GPIO_PIN_2 + GPIO_PIN_3);

        GPIOPinWrite(GPIO_PORTB_BASE, cs_pins, GPIO_PIN_3);

        SSIDataPut(SSI2_BASE, 0b10001111);
        while(SSIBusy(SSI2_BASE));
        SSIDataGet(SSI2_BASE, dummy);   //dummy thing to clear FIFO
        while(SSIBusy(SSI2_BASE));
        SSIDataPut(SSI2_BASE, 0b0); //dummy thing to clear FIFO
        while(SSIBusy(SSI2_BASE));
        SSIDataGet(SSI2_BASE, &accel_data);
        while(SSIBusy(SSI2_BASE));

        GPIOPinWrite(GPIO_PORTB_BASE, cs_pins, GPIO_PIN_2);

        SSIDataPut(SSI2_BASE, 0b10001111);
        while(SSIBusy(SSI2_BASE));
        SSIDataGet(SSI2_BASE, dummy);   //dummy thing to clear FIFO
        while(SSIBusy(SSI2_BASE));
        SSIDataPut(SSI2_BASE, 0b0); //dummy thing to clear FIFO
        while(SSIBusy(SSI2_BASE));
        SSIDataGet(SSI2_BASE, &gyro_data);
        while(SSIBusy(SSI2_BASE));

        GPIOPinWrite(GPIO_PORTB_BASE, cs_pins, GPIO_PIN_2 + GPIO_PIN_3);

        SysCtlDelay(SysCtlClockGet()/3);

    }
    return 0;
}

Hello Engiz

Glad that the code is now working for you.