Improve error reporting and handling

[matthijskooijman]

Currently, this library returns very limited error status, only STATUS_OK or STATUS_FAIL. It would be convenient if some additional codes would be returned (i.e. STATUS_NO_ACK, or STATUS_CRC_FAIL or STATUS_SHORT_READ etc.).

I considered having a go at implementing this, but since this touches on code that comes from the non-arduino-specific embedded-sps repo, which again has code from the embedded-common repo, I'm not going to figure out how all this plays together and where to contribute each part for now.

A related suggestion, is that the I2c implementation should probably check the return value of Wire.requestFrom, which returns the number of bytes actually read. I was using this library on an STM32 platform, which also has a 32-byte buffer. Currently, this makes sensirion_i2c_read silently only return 32 meaningful bytes, with the rest filled with garbage, which will then (usually) be detected by the CRC-checks, but it would be nicer if the short read was detected by itself (and with the above suggestion of different status codes, actually returned as such).

[winkj]

Agreed, that would make debugging easier. As you saw a lot of that will have to implemented in a project this one integrated, but having the issue here should help keep track.

Totally agree on checking Wire.request from, which is again in a file integrated from embedded-common.

Finally, all recent SPS versions support readout modes that fit in the 32 byte buffer, so I created issue #24 to add that in the (hopefully near) future.

[abrauchli]

Hi @matthijskooijman, you're speaking from my heart.. a better error handling would improve the developer experience. We have an issue open in our internal issue tracker. As you correctly noted, this is mostly flowing ouf of embedded-common, so if you want a placeholder to post some ideas, it'd be best to open another issue there https://github.com/Sensirion/embedded-common/issues

@rnestler FYI

[rnestler]

There was actually some work in this direction in Sensirion/embedded-common#45.