drivers: max31865: fix under zero temperature calculation #71733
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Fixes the sign on the third- and fourth-order coefficients used to calculate temperatures under zero. Verified on PT100 RTD in environmental chamber down to -55degC. Signed-off-by: Andrew Basta <[email protected]>
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did #68711 not already address this issue? this looks like this is now a double subtraction? |
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Fixes the signs on the third- and fourth-order coefficients used to calculate temperatures under zero.
Verified on PT100 RTD in environmental chamber down to -55degC.
References:
https://www.analog.com/media/en/technical-documentation/application-notes/AN709_0.pdf [See section on 'Direct Mathematical Method', relevant screenshot included here]
https://github.com/adafruit/Adafruit_MAX31865/blob/02dd3393d9750ca6e227be84b0e3b795a6941c36/Adafruit_MAX31865.cpp#L281 [Equivalent OSS implementation with correctly signed coefficients]