Add calibration via a known gas concentration. This is the recommended way
of calibrating the sensor according to the datasheet.
Signed-off-by: Jeppe Odgaard <jeppe.odgaard@prevas.dk>
The sensor does not always finish responding within 200 ms.
This is the sometimes the case when using the sensor calibrate command `X`.
Response delay up to 212 ms has been measured with a logic analyzer.
Increase the max response delay to 300 ms to fix the issue.
Signed-off-by: Jeppe Odgaard <jeppe.odgaard@prevas.dk>
During calibration feature development the following loop was used for
testing:
```shell
CMD="sensor attr_set explorir_m co2 calibration 1234"
while : ; do echo "$CMD" > /dev/ttyACM0; sleep .8; done
```
At some point calibration would fail and all following calibration commands
would fail.
Reset buffer and semaphore just before terminating the command to better
mitigate disturbance from previous failed command.
Signed-off-by: Jeppe Odgaard <jeppe.odgaard@prevas.dk>
`explorir_m_uart_flush_until_end` terminates immediately if the read
variable is initially equal to `EXPLORIR_M_MAX_RESPONSE_DELAY` and
`uart_poll_in` does not read anything.
Fix this by only checking the read variable if `uart_poll_in` reads a char.
Signed-off-by: Jeppe Odgaard <jeppe.odgaard@prevas.dk>
