TM4C1294NCPDT: ADC issues. Going into FaultISR after trying to reading a value.

Sam Panasyuk

Hello everyone, I've got a custom board I made to be used as a test fixture and i need to read values onto the ADC for various voltage things around the board. I've been having this issue for a while now and just finally going head first to figure it out, but what keeps on happening is after I (seemingly) configured everything, the MCU goes into fault ISR after trying to read back a value from the ADCs.

Here is my startup code.

  SysCtlPeripheralReset(SYSCTL_PERIPH_GPIOE);
    SysCtlPeripheralEnable(SYSCTL_PERIPH_GPIOE);
    while (!SysCtlPeripheralReady(SYSCTL_PERIPH_GPIOE)){}
    SysCtlPeripheralReset(SYSCTL_PERIPH_ADC1);
    SysCtlPeripheralEnable(SYSCTL_PERIPH_ADC1);
    while (!SysCtlPeripheralReady(SYSCTL_PERIPH_ADC1)){}
        SysCtlDelay(1000);
    GPIOPinTypeADC(GPIO_PORTK_BASE, GPIO_PIN_1);
        SysCtlDelay(1000);
    ADCClockConfigSet(ADC1_BASE, ADC_CLOCK_SRC_PLL | ADC_CLOCK_RATE_EIGHTH, 30);
        SysCtlDelay(1000);
    ADCSequenceDisable(ADC1_BASE, SEQ0);
        SysCtlDelay(1000);
    ADCSequenceConfigure(ADC1_BASE, SEQ0, ADC_TRIGGER_PROCESSOR, 0);
        SysCtlDelay(1000);
    ADCSequenceStepConfigure(ADC1_BASE, SEQ0, 0, (ADC_CTL_IE | ADC_CTL_END | ADC_CTL_CH17 | ADC_CTL_SHOLD_256)); 
        SysCtlDelay(1000);
    ADCSequenceEnable(ADC1_BASE, SEQ0);
        SysCtlDelay(1000);
    ADCIntEnable(ADC1_BASE, SEQ0);
        SysCtlDelay(1000);
    ADCIntClear(ADC1_BASE, SEQ0);
        SysCtlDelay(1000);

Here is the code that is run inside my while(1) loop (I'm trying to use the adc processor trigger mode to read values)

uint32_t *data;

            ADCProcessorTrigger(ADC1_BASE, SEQ0);
                SysCtlDelay(1000);
            while (!ADCIntStatus(ADC1_BASE, SEQ0, false)){}
                SysCtlDelay(1000);
            ADCIntClear(ADC1_BASE, SEQ0);
                SysCtlDelay(1000);
            if (!ADCSequenceOverflow(ADC1_BASE, SEQ0))
            {ADCSequenceOverflowClear(ADC1_BASE, SEQ0);}
            if (!ADCSequenceUnderflow(ADC1_BASE, SEQ0))
            {ADCSequenceUnderflowClear(ADC1_BASE, SEQ0);}
                SysCtlDelay(1000);
            ADCSequenceDataGet(ADC1_BASE, SEQ0, data);
                SysCtlDelay(1000);
            UARTprintf("AIN0 = %x\n", data[0]);

I thought there might be a problem with my clocking (seems to usually be the problem with these things), heres my main clock config.

g_ui32SysClock = SysCtlClockFreqSet((SYSCTL_OSC_MAIN | SYSCTL_XTAL_25MHZ | SYSCTL_USE_PLL | SYSCTL_CFG_VCO_240), 120000000);

And when I print g_ui32SysClock in my serial monitor I do get the value 120000000 so it seems to work properly (and I have other peripherals working on systems like I2C, SPI, and UART).

I appreciate your time and any help anyone would be willing to offer. Thanks, -Sam

over 4 years ago

0 Ralph Jacobi over 4 years ago

TI__Guru*** 135355 points

Hello Sam,

You have the following line of code:

GPIOPinTypeADC(GPIO_PORTK_BASE, GPIO_PIN_1);

But I don't see GPIO_PORTK_BASE being enabled. I think that is the cause of your FaultISR.

Best Regards,

Ralph Jacobi

0 Sam Panasyuk over 4 years ago in reply to Ralph Jacobi

Prodigy 20 points

Hello, I have enabled this port in a previous place. I have tried this with various ADC pins and their appropriate channels and the fault still occurs.

0 Ralph Jacobi over 4 years ago in reply to Sam Panasyuk

TI__Guru*** 135355 points

Hello Sam,

Okay, thanks for the clarifying. In that case please refer to this document to debug the Fault further in terms of narrowing down the root cause and report back your findings so I can further guide you on how to resolve the issue: https://www.ti.com/lit/pdf/spma043

Best Regards,

Ralph Jacobi

0 Sam Panasyuk over 4 years ago in reply to Ralph Jacobi

Prodigy 20 points

Hello, I've learned to be able to look at the NVIC_FAULT_STAT register and found that it has a value of 0x00000400 and that seems to look like the Imprecise data bit being flagged. Perhaps you can tell me what this means

0 Ralph Jacobi over 4 years ago in reply to Sam Panasyuk

TI__Guru*** 135355 points

Hello Sam,

What is the information at NVIC_MM_ADDR and NVIC_FAULT_ADDR? Sometimes those can lead to a clue even for imprecise data bus.

Sometimes an imprecise data error can result from Stack Overflow - can you check if you have enough stack assigned and that you don't have any buffers that might be overflowing?

Best Regards,

Ralph Jacobi

0 Sam Panasyuk over 4 years ago in reply to Ralph Jacobi

Prodigy 20 points

NVIC_MM_ADDR = 0xE00EDF8 and NVIC_FAULT_ADDR = 0xE00EDF8. I have some char buffer in my program that might kinda use some resources. And i believe i have increased the buffer size already to 2048 in the Properties> Arm Linker options under "Set C system stack size"

0 Bruce McKenney over 4 years ago

Guru 102725 points

Is this second block your actual code? If so, I don't see where you assign anything to "data". (Did the compiler give any Warnings?)

0 Sam Panasyuk over 4 years ago in reply to Bruce McKenney

Prodigy 20 points

Yes, on line 14 of this code ADCSequenceDataGet(ADC1_BASE, SEQ0, data); in my understanding assign the data to the uint32_t pointer "*data".

+1 Bruce McKenney over 4 years ago in reply to Sam Panasyuk

Guru 102725 points

ADCSequenceDataGet assigns "*data", but you still need to assign the variable "data". (Else there's a pretty good probability of a bus fault.)

Does it act differently if you declare data as:

> uint32_t data[8]; // "8" is maximum Sequencer size

0 Sam Panasyuk over 4 years ago in reply to Bruce McKenney

Prodigy 20 points

I think you might be some kind of embedded wizard. I knew I misunderstood something simple, just needed somebody to nudge me in the right direction. Doing that totally fixed my problem, now I can read values from the ADC correctly. Thank you.

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TM4C1294NCPDT: ADC issues. Going into FaultISR after trying to reading a value.