AnsweredAssumed Answered

AD7190 re-calibration issue

Question asked by bhawk. on Mar 28, 2012
Latest reply on Apr 3, 2012 by MaryMc

We are developing a product which uses nine AD7190's. After

the board starts, for all devices we:

 

1) issue a soft RESET (40 1's),

2) send CONFIG=000217,

3) read the ADC pre-calibration OFFSET values (we know they're going

to be 0x800000 but we like to see it anyway),

4) send the OFFSET calibration command

5) read post-calibration OFFSET values (some differences from the

post-reset values in the last two digits)

6) read pre-calibration FULLSCALE values (always reads the same)

7) send the FULLSCALE calibration command

8) read post-calibration FULLSCALE values (different from

pre-calibration values, varying from one time to the next)

9) send MODE=0x040060

10) issue a SYNC- pulse to all devices simultaneously

 

at this point, we wait for a user command and then start capturing the

conversions.

 

The problem occurs if we re-run the above sequence.  What we see is

that the pre-calibration OFFSET and FULLSCALE values return to their

reset values (as they should) after the soft RESET, but those RESET

values do _not_ change from their reset values after the second calibration. 

We have attempted various things, such as sending multiple soft RESETs

and sending multiple calibration commands, but we don't see the devices

recalibrating.

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