zenria / mh-z19-rs Goto Github PK

This library converts a u16 to bytes as follows:

(value & 0xff00 >> 8) as u8,
(value & 0xff) as u8,

However, because of operator precedence, this is actually just (value & 0xff) as u8 twice. Attempting to set detection range to 2000 (0x07D0) instead creates the number 53456 (0xD0D0).

And in set_detection_range this library tries to set the range by writing bytes 3 and 4, but the actual bytes are 6 and 7.

(Supposedly MH-Z19B actually respects bytes 4,5,6,7 as range, in which case trying to set detection range to 0-2000 is actually setting it to 0-3489660928.)

According to datasheet, another sensor from Zhengzhou Winsen Electronics Technology, MH-Z14 has the same protocol as MH-Z19. At least I can't find any differences.

I tried this crate with MH-Z14 and it reads gas concentration successfully. This is my example repo.

I didn't yet checked if Zhengzhou Winsen Electronics Technology has any other sensors with the same protocol. This is webpage that lists CO2 sensors manufactured by this company.