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Sensirion / arduino-i2c-scd4x

Arduino library for Sensirion SCD4x sensors
BSD 3-Clause "New" or "Revised" License
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What does it mean for an error code returned? #32

Closed lemorage closed 4 months ago

lemorage commented 4 months ago

I connect the SCD41 sensor and Arduino Uno board with the breadboard and run the example program from this library. The program fails. After some time of debugging, I think the problem is my scd4x.getDataReadyFlag(isDataReady) always returns 267, which is a very odd number. I haven't found any useful information explaining the error codes, and the comments for this function just say "return 0 on success, an error code otherwise".

I wonder if the returned error code has some special meaning depending on the number, just like HTTP response status codes. Or the error code itself doesn't make any sense, which just simply means there is an error somewhere.

sdmueller commented 4 months ago

Hi @lemorage

The error codes are platform dependent. I2C in general only knows success or fail. However, our Arduino drivers use the arduino-core library which has its own error codes defined in SensirionErrors.h.

If you use the example program as is, the error code will be translated via the errorToString function and you should see the resulting error also as text.

Where the error seems to come from in your case: scd4x.getDataReadyFlag uses SensirionI2CCommunication::sendFrame from arduino-core, which has some error handling. 267 is the bitwise OR combination of the high level error WriteError and the low level error I2cAddressNack. This means that there was no response on the I2C address you used. But errorToString should translate that already for you.

Hope this helps!

lemorage commented 4 months ago

Ohh, thank you for your detailed explanation! I suspected there should be something wrong with the I2C devices, but I couldn't find the exact reason. The program just didn't print anything when errorToString(error, errormsg, 256); was there, and I had to manually print the return value of scd4x.getDataReadyFlag to see if it was 0. So I really thought hard to figure out what is the sense of this error number.