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MSP430FR2672: Linearization of touch slider

Part Number: MSP430FR2672


Our design is using a touch slider that is directly mapped back to a visual UI element. When we try to integrate the slide with the UI element we are not seeing a 1:1 mapping. We have 30 discrete LED positions laid out with our touch slider parallel to the LEDs. We are seeing significant non-linearity with the reported touch positions.

The below plot shows the ideal mapping of the reported touch position in blue (a straight line) and the mapping with our touch slider trim set to 0 & 29 and 2 & 27.

How can we go about linearlizing the slider algorithm so that we get a linear readout?

We have gone through the tuning process detailed in app note SLAA842B, and have excellent SNR numbers, and are getting the desired deltas for a slider or wheel implementation. But I cannot find anything on this topic specifically.

Attached is an excel file with some test data that includes the reported slider position as well as the raw data for each slider element. I have also included the SNR report for the touch implementation which provides a glimpse into the signal level differences of each element.




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