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 available 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:

In the response the first 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 * 256 + 03. .. followed by two byte for CRC.