F28035 ADC Zero Offset Calibration

Josip Babic

Other Parts Discussed in Thread: TMS320F28035

Hi all,

I'm having trouble converting VREFLO on B5 analog input of TMS320F28035. I’m running the “Example_2803xAdcSoc” example where I added “AdcOffsetSelfCal()” call after “Device_cal()” in “InitAdc()” function.

B5 in AdcOffsetSelfCal() converts to 0FFFh all 16 times (I checked ADCRESULTx registers). This leads to ADCOFFTRIM register value of 81, which is wrong. If I tie A0 input to VREFLO and replace “AdcChanSelect(13)” in the self calibration function with “AdcChanSelect(0)”, everything seems fine and there is no offset in later conversions.

I tried running the code on TI’s controlCard and on two of our boards containing F28035, with the same results.

Am I doing something wrong?

Regards,

Josip

over 13 years ago

0 Devin Cottier over 13 years ago

TI__Guru 60865 points

Most likely the ADC is not powered up. Please ensure that the ADC power bits are set to 1 in the ADCCTL1 register and that you wait the specified 1ms power up time before you perform the self cal.

0 Josip Babic over 13 years ago in reply to Devin Cottier

Intellectual 700 points

Devin,

sorry for the long delay, I was tied up in another project. You are right, I foolishly added “AdcOffsetSelfCal()” call before the ADC power-up code in “InitAdc()” function.

Thank you,

Josip

0 Devin Cottier over 13 years ago in reply to Josip Babic

TI__Guru 60865 points

Glad to hear you were able to resolve the issue.

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F28035 ADC Zero Offset Calibration