F28031,the ADC conversion result is not correct

blank flank

I‘m using a TI DSP320F28031 chip, ADC acquisition voltage value and the actual value of the multimeter measurement deviation is very big,

change another slice of chip is also so.

ps: the program is the Example_2803xADCSOC routines. What could be the problem?

-flank

over 12 years ago

0 tlee over 12 years ago

TI__Guru 62975 points

flank,

Can you give us a rough estimate of how far the pin voltage deviates from the ADC conversion? Are you able to use an oscilloscope on the pin during ADC conversion to see if the signal might be drooping while the ADC is sampling?

-Tommy

0 blank flank over 12 years ago in reply to tlee

Prodigy 30 points

Tommy:

i think i got the problem : i used an low impedance oscilloscope to sample one pin voltage , and the AD pin perpheral impedance should be 50K ohm or more.

this should influence the measurement result.

The other reason should be:

the SOC S/H Window which i set was not suitable. It should be:

AdcRegs.ADCSOC0CTL.bit.ACQPS = 32;

AdcRegs.ADCSOC1CTL.bit.ACQPS = 32;

it seems that the F28031 chip should better setting like this?

now use an oscilloscope on the pin during ADC conversion,

the signal value is stable.

In Addition,

offset voltage between the pin voltage sampled from the oscilloscope and the ADC conversion is about 10mV.

Thanks.

--flank

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F28031,the ADC conversion result is not correct