TEMPMON drowns i.MXRT1064 in interrupts

[StanAk]

Hello,

We're trying to deploy temperature monitor in our project that uses i.MXRT1064. We initialize TEMPMON using SDK example; everything goes well until the very first High Temp interrupt. Then the processor basically goes into interrupt spree, calling TEMP_LOW_HIGH_IRQHandler over and over again. Inspired by this post in the NXP Community we've reduced the ISR to the following, what are we missing?

void TEMP_LOW_HIGH_IRQHandler(void)
{
    uint32_t const cleanS0 = TEMPMON->TEMPSENSE0 & ~TEMPMON_TEMPSENSE0_ALARM_VALUE_MASK;
    uint32_t const cleanS2 = TEMPMON->TEMPSENSE2 & ~TEMPMON_TEMPSENSE2_LOW_ALARM_VALUE_MASK;

    // Clear alarm values
    TEMPMON->TEMPSENSE0 = cleanS0;
    TEMPMON->TEMPSENSE0 = cleanS0 | TEMPMON_TEMPSENSE0_ALARM_VALUE(1U);         // Low count (high temperature)
    TEMPMON->TEMPSENSE2 = cleanS2;
    TEMPMON->TEMPSENSE2 = cleanS2 | TEMPMON_TEMPSENSE2_LOW_ALARM_VALUE(0xFFEU); // High count (small temperature)

    SDK_ISR_EXIT_BARRIER;
}

Also is our assumption that ISR will execute at the TEMPMON measure frequency incorrect? We're setting the divider/frequency value to 49152 for 32KHz RTC Clock, which should correspond to 1500ms measure rate. Yet the interrupts seem to fire faster than every 1 ms.

[StanAk]

I am attaching a full example to this Reply:

#include "fsl_debug_console.h"
#include "fsl_tempmon.h"
#include "fsl_clock.h"

extern void BOARD_ConfigMPU(void);
extern void BOARD_InitPins(void);
extern void BOARD_BootClockRUN(void);
extern void BOARD_InitDebugConsole(void);

volatile bool isrTripped = false;

void TEMP_LOW_HIGH_IRQHandler(void)
{
    isrTripped = true;
    TEMPMON_SetTempAlarm(TEMPMON, 120U, kTEMPMON_HighAlarmMode);  // Expand threshold to 120 deg C to stop tripping
    SDK_ISR_EXIT_BARRIER;
}

int main(void)
{
    uint32_t rtcClockFreq_hz;
    float measFreq_hz;
    float clockDividerValue;
    tempmon_config_t config;
    float tempDegC;

    /* Board pin, clock, debug console init */
    BOARD_ConfigMPU();
    BOARD_InitPins();
    BOARD_BootClockRUN();
    BOARD_InitDebugConsole();

    // Tempmon Init
    rtcClockFreq_hz = CLOCK_GetFreq(kCLOCK_RtcClk);
    measFreq_hz = 1 / 1.5F; // Measure every 1.5 seconds
    clockDividerValue = rtcClockFreq_hz / measFreq_hz;

    TEMPMON_GetDefaultConfig(&config);
    config.frequency = (uint16_t)clockDividerValue; // Per UM .frequency is the RTC Clock divider
    config.panicAlarmTemp  = 85U;
    config.highAlarmTemp = 80U;
    config.lowAlarmTemp  = 5U;
    PRINTF("Configuring TEMPMON for %X freq, [%d, %d] deg C \r\n", config.frequency, config.lowAlarmTemp, config.highAlarmTemp);

    TEMPMON_Init(TEMPMON, &config);
    TEMPMON_StartMeasure(TEMPMON);
    EnableIRQ(TEMP_LOW_HIGH_IRQn);
    NVIC_SetPriority(TEMP_LOW_HIGH_IRQn, 31U);

    // Lower the high temperature threshold to kick off the ISR
    SDK_DelayAtLeastUs(3000000U, CLOCK_GetCpuClkFreq());
    tempDegC = TEMPMON_GetCurrentTemperature(TEMPMON);
    config.highAlarmTemp = (uint32_t)tempDegC - 1U;
    PRINTF("Current temperature at %d degC, dropping thresholds to [%d, %d]\r\n", (int16_t)tempDegC, config.lowAlarmTemp, config.highAlarmTemp);
    TEMPMON_SetTempAlarm(TEMPMON, config.highAlarmTemp, kTEMPMON_HighAlarmMode);

    for (;;)
    {
        static uint32_t tripCounter = 0U;
        if (isrTripped)
        {
            isrTripped = false;
            tempDegC = TEMPMON_GetCurrentTemperature(TEMPMON);
            PRINTF("{%d degC, SENSE0=%X}\r\n", (int16_t)tempDegC, TEMPMON->TEMPSENSE0);

            if (++tripCounter > 2U)
            {
                DisableIRQ(TEMP_LOW_HIGH_IRQn);
                PRINTF("Interrupt manually disabled. Re-enabling in 3s...\r\n");
                tripCounter = 0U;
                SDK_DelayAtLeastUs(3000000U, CLOCK_GetCpuClkFreq());
                EnableIRQ(TEMP_LOW_HIGH_IRQn);
            }
        }
    }
}

I expect interrupts to stop when threshold is expanded in line 15. However, the following anomalies are observed:

• Interrupts keep coming
• Interrupts are triggering at a (much) faster rate than 1.5 seconds
• When interrupts are manually disabled and then re-enabled later they get triggered again despite conditions not met

Output:

Configuring TEMPMON for C000 freq, [5, 80] deg C
Current temperature at 41 degC, dropping thresholds to [5, 40]
{40 degC, SENSE0=F004EA02}
{40 degC, SENSE0=F004EA02}
{40 degC, SENSE0=F004EA02}
Interrupt manually disabled. Re-enabling in 3s...
{40 degC, SENSE0=F004EA02}

[CarlosGarabito]

Check this post, is talking about the same

https://community.nxp.com/t5/i-MX-RT/RT1050-Temperature-Monitor-Panic-Temperature/m-p/844404

Best Regards

[StanAk]

@CarlosGarabito thank you for your response. I went over the post in the link that you've provided and I don't believe the two issues are related. Dev on the other end had a user error in their code (specified wrong address). I've also double checked the memory map as suggested in that post and confirmed that it is valid.

[CarlosGarabito]

Well on SDK, we have an example, which you can use, did you try it?, you can find it, on the import SDK example and driver_examples, temperaturemonitor.