Evaluating the CO2-Sensor S8 from SenseAir. https://senseair.com/products/size-counts/s8-5/
Code for Arduino (.ino) with some routines to read all register and another code for esp-idf in C. (.c)
There is no standard library aviable now - since the functionality / documentation is poor.
Send a request like {0xFE, 0X04, 0X00, 0X03, 0X00, 0X01, 0XD5, 0XC5} and
wait for the response like {0xFE, 0X04, 0X02, 0X03, 0X88, 0XD5, 0XC5}.
Where:
| byte | example | description on request |
|---|---|---|
| 0 | 0xFE | any Address |
| 1 | 0x04 | function code (03 read hold reg / 04 read inp. register / 06 write) |
| 2, 3 | 0x00 0x03 | starting Address |
| 4, 5 | 0x00 0x01 | lenght of requested register |
| 6, 7 | 0xD5 0xC5 | CRC low / high |
In the response the frist two byte are the same as in the request 0xFE and 0x04.
The requested value is in byte 3 and 4 (0x03) and (0x88) with low-byte first. so 88 * 265 + 03.
.. followed by two byte for CRC.