TMS320F28P650SK: GPIO status measurement after device power on

Hi expert,

Any chance to have some input here.

Thanks,

Johnny

Hello,

The GPIO/muxed pins default to GPIO‐input (high‐impedance) on reset / power‐on. High impedance means the pin is not actively driven (source or sink) by the MCU, so in principle it should float. Thus, the behavior you observe is not inherently impossible per the device‐spec; but getting ~3.3 V high enough to drive something suggests either there is an external circuit pulling it up, or direct internal clamping is involved. Is VDDIO / I/O supply coming up before or with the main chip? If some supplies are present, some internal circuits may be powered earlier, enabling bias or ESD clamp to act.

Also, in some boot code or debug ROMs / startup sequences, pins might be configured or special code run before your GPIO init. Using a debug GPIO marker is good, but ensure no other early initialization touches it.

Best Regards,

Masoud

Hi Masoud,

Masoud Farhadi said:

The GPIO/muxed pins default to GPIO‐input (high‐impedance) on reset / power‐on. High impedance means the pin is not actively driven (source or sink) by the MCU, so in principle it should float.

I totally agree with you.

However, I duplicate customer's issue with internal App's team 100-pin VDB (socket board).

Indeed see the GPIO92 has a clear 3.3V during power on to user code dependent. 

(1). Would you kindly test it with our 100-pin VDB as well ?

(2). We trial and error, removing two pins' initialization in board_init(), and put those pins initialization code back in few lines later (attached code), then the 3.3V on GPIO92 was gone tested on 100-pin VDB.

EPWM3 A (GPIO 4 / Pin 93)

EPWM14 A (GPIO 203 / Pin 11)

Board_init();
    GPIO_writePin(DEBUG_GPIO, 1);
    I2CFIFO_Init();
    LCD_Init();
    EALLOW;
    GPIO_setPinConfig(DD_EPWM_EPWMA_PIN_CONFIG);
    GPIO_setPadConfig(DD_EPWM_EPWMA_GPIO, GPIO_PIN_TYPE_STD);
    GPIO_setQualificationMode(DD_EPWM_EPWMA_GPIO, GPIO_QUAL_SYNC);

    GPIO_setPinConfig(DD_EPWM_EPWMB_PIN_CONFIG);
    GPIO_setPadConfig(DD_EPWM_EPWMB_GPIO, GPIO_PIN_TYPE_STD);
    GPIO_setQualificationMode(DD_EPWM_EPWMB_GPIO, GPIO_QUAL_SYNC);
    EPWM_setEmulationMode(DD_EPWM_BASE, EPWM_EMULATION_FREE_RUN);
    EPWM_setClockPrescaler(DD_EPWM_BASE, EPWM_CLOCK_DIVIDER_1, EPWM_HSCLOCK_DIVIDER_1);
    EPWM_setTimeBasePeriod(DD_EPWM_BASE, 999);
    EPWM_setTimeBaseCounter(DD_EPWM_BASE, 0);
    EPWM_setTimeBaseCounterMode(DD_EPWM_BASE, EPWM_COUNTER_MODE_UP);
    EPWM_disablePhaseShiftLoad(DD_EPWM_BASE);
    EPWM_setPhaseShift(DD_EPWM_BASE, 0);
    EPWM_setSyncInPulseSource(DD_EPWM_BASE, EPWM_SYNC_IN_PULSE_SRC_DISABLE);
    EPWM_setSyncPulseSource(DD_EPWM_BASE, HRPWM_PWMSYNC_SOURCE_ZERO);
    EPWM_setCounterCompareValue(DD_EPWM_BASE, EPWM_COUNTER_COMPARE_A, 0);
    EPWM_setCounterCompareShadowLoadMode(DD_EPWM_BASE, EPWM_COUNTER_COMPARE_A, EPWM_COMP_LOAD_ON_CNTR_ZERO);
    EPWM_setCounterCompareValue(DD_EPWM_BASE, EPWM_COUNTER_COMPARE_B, 0);
    EPWM_setCounterCompareShadowLoadMode(DD_EPWM_BASE, EPWM_COUNTER_COMPARE_B, EPWM_COMP_LOAD_ON_CNTR_ZERO);
    EPWM_setActionQualifierAction(DD_EPWM_BASE, EPWM_AQ_OUTPUT_A, EPWM_AQ_OUTPUT_HIGH, EPWM_AQ_OUTPUT_ON_TIMEBASE_ZERO);
    EPWM_setActionQualifierAction(DD_EPWM_BASE, EPWM_AQ_OUTPUT_A, EPWM_AQ_OUTPUT_NO_CHANGE, EPWM_AQ_OUTPUT_ON_TIMEBASE_PERIOD);
    EPWM_setActionQualifierAction(DD_EPWM_BASE, EPWM_AQ_OUTPUT_A, EPWM_AQ_OUTPUT_LOW, EPWM_AQ_OUTPUT_ON_TIMEBASE_UP_CMPA);
    EPWM_setActionQualifierAction(DD_EPWM_BASE, EPWM_AQ_OUTPUT_A, EPWM_AQ_OUTPUT_NO_CHANGE, EPWM_AQ_OUTPUT_ON_TIMEBASE_DOWN_CMPA);
    EPWM_setActionQualifierAction(DD_EPWM_BASE, EPWM_AQ_OUTPUT_A, EPWM_AQ_OUTPUT_NO_CHANGE, EPWM_AQ_OUTPUT_ON_TIMEBASE_UP_CMPB);
    EPWM_setActionQualifierAction(DD_EPWM_BASE, EPWM_AQ_OUTPUT_A, EPWM_AQ_OUTPUT_NO_CHANGE, EPWM_AQ_OUTPUT_ON_TIMEBASE_DOWN_CMPB);
    EPWM_setActionQualifierAction(DD_EPWM_BASE, EPWM_AQ_OUTPUT_B, EPWM_AQ_OUTPUT_HIGH, EPWM_AQ_OUTPUT_ON_TIMEBASE_ZERO);
    EPWM_setActionQualifierAction(DD_EPWM_BASE, EPWM_AQ_OUTPUT_B, EPWM_AQ_OUTPUT_NO_CHANGE, EPWM_AQ_OUTPUT_ON_TIMEBASE_PERIOD);
    EPWM_setActionQualifierAction(DD_EPWM_BASE, EPWM_AQ_OUTPUT_B, EPWM_AQ_OUTPUT_NO_CHANGE, EPWM_AQ_OUTPUT_ON_TIMEBASE_UP_CMPA);
    EPWM_setActionQualifierAction(DD_EPWM_BASE, EPWM_AQ_OUTPUT_B, EPWM_AQ_OUTPUT_NO_CHANGE, EPWM_AQ_OUTPUT_ON_TIMEBASE_DOWN_CMPA);
    EPWM_setActionQualifierAction(DD_EPWM_BASE, EPWM_AQ_OUTPUT_B, EPWM_AQ_OUTPUT_LOW, EPWM_AQ_OUTPUT_ON_TIMEBASE_UP_CMPB);
    EPWM_setActionQualifierAction(DD_EPWM_BASE, EPWM_AQ_OUTPUT_B, EPWM_AQ_OUTPUT_NO_CHANGE, EPWM_AQ_OUTPUT_ON_TIMEBASE_DOWN_CMPB);
    EPWM_setRisingEdgeDelayCountShadowLoadMode(DD_EPWM_BASE, EPWM_RED_LOAD_ON_CNTR_ZERO);
    EPWM_disableRisingEdgeDelayCountShadowLoadMode(DD_EPWM_BASE);
    EPWM_setFallingEdgeDelayCountShadowLoadMode(DD_EPWM_BASE, EPWM_FED_LOAD_ON_CNTR_ZERO);
    EPWM_disableFallingEdgeDelayCountShadowLoadMode(DD_EPWM_BASE);
    EPWM_setTripZoneAction(DD_EPWM_BASE, EPWM_TZ_ACTION_EVENT_TZA, EPWM_TZ_ACTION_LOW);
    EPWM_setTripZoneAction(DD_EPWM_BASE, EPWM_TZ_ACTION_EVENT_TZB, EPWM_TZ_ACTION_LOW);
    EPWM_enableADCTrigger(DD_EPWM_BASE, EPWM_SOC_A);
    EPWM_setADCTriggerSource(DD_EPWM_BASE, EPWM_SOC_A, EPWM_SOC_TBCTR_ZERO);
    EPWM_setADCTriggerEventPrescale(DD_EPWM_BASE, EPWM_SOC_A, 1);
    EDIS;

Thanks, 

Johnny

Johhny,

I tried this on a controlCARD, with different package, but still looking at GPIO92(pin 99 on 100 pin device).  In Wait Boot or even flash boot with no code loaded I don't see any glitching on that pin.

I think it must be SW setup related; is it possible to attached the entire project to this post(or send it to me via email) so I can try to duplicate it?  I'm not sure how changing the order of operations for other GPIOs should influence GPIO92.  

Is the PWM setup before the mux is configured for ePWM output?  Perhaps as we are setting up the PWM, if GPIO92 is already connected to the PWM logic we will see some state change until we are complete.

Best,

Matthew