SAADC: TASKS_CALIBRATEOFFSET shall only be used before TASKS_START or after EVENTS_END nRF52833

[maya_sa]

Hi. I was wandering if there is a difference if I put the TASKS_CALIBRATEOFFSET before TASKS_START , and vise versa.
However, I saw in this link: infocenter.nordicsemi.com/index.jsp that the TASKS_CALIBRATEOFFSET must come before the TASKS_START , and I am wondering why. (all I found out was that this is an anomaly inherited from the previous IC revision.
Thank you

[Karl Ylvisaker]

Hello,

I was wandering if there is a difference if I put the TASKS_CALIBRATEOFFSET before TASKS_START , and vise versa.

I am not sure I understand the question here - there is a difference if TASKS_CALIBRATEOFFSET is triggered after TASKS_START, as mentioned in the Errata description.

TASKS_CALIBRATEOFFSET must come before the TASKS_START , and I am wondering why. (all I found out was that this is an anomaly inherited from the previous IC revision.

Yes, as written in the Errata 237 that you reference; if you trigger TASKS_CALIBRATEOFFSET between TASKS_START and TASKS_END, then you will see unexpected samples written to your RAM. This is the reason why you will need to avoid triggering TASKS_CALIBRATEOFFSET between TASKS_START and TASKS_END.
The workaround for this errata - to avoid seeing unexpected samples written to RAM - is to only ever trigger TASKS_CALIBRATEOFFSET either before TASKS_START or after TASKS_END, i.e when the SAADC is not actively in use.

Please let me know if I misunderstood any part of your question.

Best regards,
Karl

[maya_sa]

Thank you for the answer Karl.

I am wondering why this is happening - why  if you trigger TASKS_CALIBRATEOFFSET between TASKS_START and TASKS_END, then you will see unexpected samples written to your RAM. 

Thank you 

Maya

[Karl Ylvisaker]

maya_sa said:

Thank you for the answer Karl.

No problem at all, Maya, I am happy to help!

maya_sa said:

why  if you trigger TASKS_CALIBRATEOFFSET between TASKS_START and TASKS_END, then you will see unexpected samples written to your RAM. 

I am not certain of the intrinsic details here unfortunately, but my guess would be that the sample(s) generated during calibration is not discarded properly since the TASKS_START task has already been triggered and the SAADC is currently working / sampling, or something similar. This is however just my personal initial guess at what is happening, and I am in no way certain that this is what is actually causing this.

Is there a specific need or requirement that causes you to wonder about this? If so, please elaborate so I may understand the issue better, and better help you resolve it.

Best regards,
Karl

[maya_sa]

Thank you very much Karl!

[Karl Ylvisaker]

No problem at all, Maya!

Please do not hesitate to open another ticket if you should encounter any other issues or questions in the future.

Good luck with your development!

Best regards,
Karl