[ts-7000] Bad distortions on MAX197 readings (via adc_logger)

["j.chitte" <>]

Hi,

On my 7250 I have an R2R network DAC running of 4 bits of portA . 
This is far more linear than I expected from such a simple circuit. 
An on screen plot looks as straight as a die.

However , I am monitoring it with one channel of the MAX ADC
and there is some very bad distortion of the values it returns.

http://piments.com/holding/badDAC.svg

I have verified the voltage my circuit is presenting at the header 
pin going to the 7250 and it is as expected for all values. 

I am reading it with a modified adc_logger so the guts of the IO is 
pretty simple and close to ts7200io.c 

Is this the question of calibration that was mentioned earlier in 
relation to these boards?

TIA. 






 
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