TMS320F28P550SJ: The ADC result register value suddenly changes to a very small value

Hi Zhang,

Did you scope the input signal on ADC and verified its always present?

Are you using internal or external VREFHI (voltage reference)? Please double check configuration of this.

Thanks,

Susmitha

Hi Susmitha, 

Customer side use external reference voltage, We scope the input signal on ADC pin but didn't find noise from the waveform. External reference voltage is also stable. Regarding the ADC configuration, it is migrated from their last-gen F280049.

We don't have clue to figure out the root cause now. Could you please share some suggestions to help us? Thanks!

BR,

Fengyu

Hi Fengyu,

Can you please share your part of code, where ADC Is configured?

Thanks,
Susmitha

HI Susmitha,

28p55 150M, the ADC configuration as follows, sample frequency is 80K, 12.5us.

    EALLOW;
    ADC_setOffsetTrim(ADCA_BASE);
    ADC_setOffsetTrim(ADCB_BASE);
    ADC_setOffsetTrim(ADCC_BASE);
    ADC_setOffsetTrim(ADCD_BASE);
    ADC_setOffsetTrim(ADCE_BASE);
    EDIS;

    EALLOW;
    ADC_setVREF(ADCA_BASE, ADC_REFERENCE_EXTERNAL, ADC_REFERENCE_2_5V);
    ADC_setVREF(ADCB_BASE, ADC_REFERENCE_EXTERNAL, ADC_REFERENCE_2_5V);
    ADC_setVREF(ADCC_BASE, ADC_REFERENCE_EXTERNAL, ADC_REFERENCE_2_5V);
    ADC_setVREF(ADCD_BASE, ADC_REFERENCE_EXTERNAL, ADC_REFERENCE_2_5V);
    ADC_setVREF(ADCE_BASE, ADC_REFERENCE_EXTERNAL, ADC_REFERENCE_2_5V);
    EDIS;

    EALLOW;
    //
    //
    AdcaRegs.ADCCTL2.bit.PRESCALE = 8;
    AdcbRegs.ADCCTL2.bit.PRESCALE = 8;
    AdccRegs.ADCCTL2.bit.PRESCALE = 8;
    AdcdRegs.ADCCTL2.bit.PRESCALE = 8;
    AdceRegs.ADCCTL2.bit.PRESCALE = 8;
    //
    //
    AdcaRegs.ADCCTL1.bit.INTPULSEPOS = 1;
    AdcbRegs.ADCCTL1.bit.INTPULSEPOS = 1;
    AdccRegs.ADCCTL1.bit.INTPULSEPOS = 1;
    AdcdRegs.ADCCTL1.bit.INTPULSEPOS = 1;
    AdceRegs.ADCCTL1.bit.INTPULSEPOS = 1;

    //
    //
    AdcaRegs.ADCCTL1.bit.ADCPWDNZ = 1;
    AdcbRegs.ADCCTL1.bit.ADCPWDNZ = 1;
    AdccRegs.ADCCTL1.bit.ADCPWDNZ = 1;
    AdcdRegs.ADCCTL1.bit.ADCPWDNZ = 1;
    AdceRegs.ADCCTL1.bit.ADCPWDNZ = 1;
    EDIS;
    
    
    AdcbRegs.ADCSOC0CTL.bit.TRIGSEL = 0x11;
    AdcbRegs.ADCSOC0CTL.bit.ACQPS = 0x28;          
    AdcbRegs.ADCSOC0CTL.bit.CHSEL = ADCIv; //b1
    
    AdccRegs.ADCSOC2CTL.bit.TRIGSEL = 0x11;    
    AdccRegs.ADCSOC2CTL.bit.ACQPS = 0x28;         
    AdccRegs.ADCSOC2CTL.bit.CHSEL = ADCIw; //c4             

    AdccRegs.ADCSOC5CTL.bit.TRIGSEL = 0x11;    
    AdccRegs.ADCSOC5CTL.bit.ACQPS = 0x28;         
    AdccRegs.ADCSOC5CTL.bit.CHSEL = ADCIu; //c14             
    
    AdcaRegs.ADCSOCPRICTL.bit.RRPOINTER = 0x0f;
    AdcbRegs.ADCSOCPRICTL.bit.RRPOINTER = 0x0f;
    AdccRegs.ADCSOCPRICTL.bit.RRPOINTER = 0x0f;
    AdcdRegs.ADCSOCPRICTL.bit.RRPOINTER = 0x0f;
    AdceRegs.ADCSOCPRICTL.bit.RRPOINTER = 0x0f;

    AdcaRegs.ADCSOCPRICTL.bit.SOCPRIORITY = 0x10;
    AdcbRegs.ADCSOCPRICTL.bit.SOCPRIORITY = 0x10;
    AdccRegs.ADCSOCPRICTL.bit.SOCPRIORITY = 0x10;
    AdcdRegs.ADCSOCPRICTL.bit.SOCPRIORITY = 0x10;
    AdceRegs.ADCSOCPRICTL.bit.SOCPRIORITY = 0x10;
    
    
   EPwm7Regs.ETSEL.bit.SOCAEN = 1;              //
   EPwm7Regs.ETSEL.bit.SOCASEL = ET_CTR_ZERO;   //80K=12.5us
   EPwm7Regs.ETPS.bit.SOCAPRD = ET_1ST;         //

Hi Zhang,

Can you please refer to this thread

TMS320F28P559SJ-Q1: P55x external voltage reference for ADC setting - C2000 microcontrollers forum - C2000︎ microcontrollers - TI E2E support forums

Can you check Rev of board by confirming the value at address 0x5D00C? 

Thanks,
Susmitha

Hi Susmitha,

The REV of the board is 1, shown at  address 0x5D00C. Is the version normal?

BR,

Fengyu

Hi Zhang,

(+) TMS320F28P559SJ-Q1: P55x external voltage reference for ADC setting - C2000 microcontrollers forum - C2000︎ microcontrollers - TI E2E support forums

Please refer to this thread on how to configure ADC when using external reference in above conditions.

Thanks,

Susmitha

Hi Susmitha,

They are not the same question. We have already configured 2.5V reference. You can refer to the code Zhang shared before. Do you have other suggestions?

BR,

Fengyu

Hi Fengyu,

When using external reference and REV of the board is 1.There need to be made some modifications. Can you confirm if your code has same?

Please make below changes:

• If the revision ID (value at address 0x5D00C) is "1" then define the REV_ID as a predefined symbol in the projectspec and (Add "--define=REV_ID=1" in the compiler flags, which correspond to REV0
• Also,Inside sysctrl.h we defined the location of Device_cal 

           #define Device_cal ((void (void))((uintptr_t)0x003fb1e7)) . please make sure, you have same value.

On F28P55x, when the external reference mode is selected, the ANAREFx1P65SEL bit should be set to 0 for FSR = VREFHI.

Setting the ANAREFx1P65SEL bit to 1 will cause FSR=2xVREFHI if we are applying externally 1.65V. But since you already applied 2.5V externally, the bit should be set to 0. 

 Can you incorporate these changes and try running the same?

Thanks,
Susmitha