CN0510 calibration reporting integers

Question

Hi there, 
 
 I am not getting repeatable values from the BAT_IMPEDANCE example. this is the result after trying 12 consecutive runs. All over the place:

This is my test set-up:

The calibration results are giving integers and appear to be nonsense

Freq 
 Vexcite 
 Vcal

10.00 
 3.000 
 0.000

16.68 
 3.000 
 0.000

27.83 
 3.000 
 -1.000

46.42 
 -4.000 
 -7.000

77.43 
 0.000 
 -1.000

129.15 
 -1.000 
 -1.000

215.44 
 -1.000 
 0.000

359.38 
 2.000 
 1.000

599.48 
 -2.000 
 13.000

1000.00 
 2.000 
 13.000

What I've tried: 
 - the basic sample here: 
 https://github.com/analogdevicesinc/ad5940-examples/tree/master/examples/AD5940_BATImpedance 
 
 - adding the extra params to the struct mentioned in fig here: 
 https://wiki.analog.com/_detail/resources/eval/user-guides/circuits-from-the-lab/cn0510/serial-terminal.png?id=resources%3Aeval%3Auser-guides%3Acircuits-from-the-lab%3Acn0510 
 
 - pasting in the code here: 
 https://ez.analog.com/reference-designs/f/q-a/558951/cn0510-batz-frequency-inconsistency/465899?queryID=6cdfcae6848782175348960c6a40f782 
 
 I guess something is wrong with my ADC. What options do I have to troubleshoot? 
 
 Thank you, take care,

graial · Accepted Answer

Good evening Akila, 
 
 Good news! I'm now getting repeatable measurements which seem at least plausible considering the circuits involved. 
 Impedance of the calibration circuit now has a magnitude of: 
 with NiMH cell - 410-bits (-1.208V) 
 open-circuit - 23-bits (-1.222V) *if my conversion is correct* 
 and the curves behave reasonably. 
 ------- 
 Now both of my calibration responses are much larger than what you showed in your screenshot from Mar 6. I plotted them in one of the tabs for comparison. 
 Does the calibration data now being reported look reasonable to you? 
 Here's the data: 
 XLSX 
 
 I honestly don't know what happened. It was just working when I tried to run my first tests on arriving in the lab this morning. The device was with me the whole time. Nobody else touched it. 
 -------------- 
 Akila said: This is the default link for current github lib files: https://github.com/analogdevicesinc/ad5940lib (1) 
 What I shared above is different from this lib file. (2) 
 You are using a lib file in Github branch which is different from both (1) and (2) files. 
 I see now that i didn't notice the changes in git diff because the lib is a submodule. 
 However, both code samples are now measuring correctly. Not at all similar to what I posted on Mar 13 
 ---------- 
 You will notice if you check the 'sensor pal' tab though, that sensor pal is still reporting gibberish on this device. But I'm not going to chase that for now. 
 ----------- 
 I spent some time trying to re-trace my steps and reproduce the earlier erroneous results. After everything I tried today, I was still getting repeatable, reasonable results 
 Maybe it was a corrupted build artifact or something. At any rate, I'm very glad to see this now working. 
 Thank you for all of your assistance. I'm going to open a PR suggesting a slightly different serial output that might help someone new to the device have a better clue as to what is going on. 
 
 Take care, 
 Allan)

Electronic Design Services - PartnerZone

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CN0510 calibration reporting integers

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