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Part Number: MSP430FR2633
I am trying to figure out what formula does the MSP430FR2633 controller follow to convert capacitance into counts. I read at another post that this controller is particularly good at sensing change in capacitance. So, how can I calculate analytically the conversion of delta in capacitance to delta in counts? What I am trying to do is create a script that will automate the calculation of the conversion count and conversion gain, providing as input the relative change in capacitance before and after touch, and the targeted sensitivity. I do take into consideration parasitic capacitance from traces as well.
Thank you in advance,
In reply to Dennis Lehman:
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Hello Dennis,Thank you, your answer was very enlightening.I will try to duplicate what you describe. I have a question: The known capacitors that you used (1pF and 1.5pF) , are the reference capacitors of the CapTIvate peripheral ?Konstantinos
In reply to Konstantinos Bazirgiannis:
I attached my code. Should give you some idea how to setup and use the internal ref caps.
I was curious if you are making progress.
Hi Dennis,Thanks for your quick response.I will do the experiment on Monday and I'll get back to you as soon as I am done.Konstantinos
I haven’t heard from you for a couple of days now, so I’m assuming you were able to get everything working the way you wanted.If this isn’t the case, please click the "This did NOT resolve my issue" button and reply to this thread with more information.If this thread locks, please click the "Ask a related question" button and in the new thread describe the current status of your issue and any additional details you may have to assist us in helping to solve your issues.
Hello Dennis,I am sorry for the delay, but in the last week I didn't have much time to replicate your suggestions. I am on it this week and I'll post my findings as soon as I am done.Konstantinos
I’ve tested the procedure you recommended and everything is working as expected. e.g. for conv_count = 500 and conv_gain = 100 I measure 493 for the LTA and when I connect the 1pF ref cap the counts drop at 274 resulting in 16.2% change and 6.2 pF baseline capacitance. Likewise, for the sets of values 500-200, 600-100 and 600-200 I get essentially the same percentage change. Thanks a lot for your guidance.
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