Incorrect humidity value for Govee H5072/75 when temperature below 0 degree celsius

[radioyear]

Hi,

I noticed that the reading for the humidity value for a Govee H5075 jumps to a wrong value when temperature falls below 0 degree celsius. The humidity value in the Govee app meanwhile remains correct.

I think this happens because in case of negative temperature values you have to substract 8388608 (0x800000) from the basenumber to get the right temperature value. The humidity value then also has to be derived from this corrected basenumber. But in H5072_json.h the original basenumber is used for humidity and we get a wrong value.

With this change in H5072_json.h I get correct humidity readings:

const char* _H5072_json = [...], \"hum\":{\"condition\":[\"manufacturerdata\",6,\"bit\",3,0],\"decoder\":[\"value_from_hex_data\",\"manufacturerdata\",6,6,false,false],\"post_proc\":[\"%\",1000,\"/\",10]},\"_hum\":{\"condition\":[\"manufacturerdata\",6,\"bit\",3,1],\"decoder\":[\"value_from_hex_data\",\"manufacturerdata\",6,6,false,false],\"post_proc\":[\"-\",8388608,\"%\",1000,\"/\",10]},....

  "hum":{
     "condition":["manufacturerdata", 6, "bit", 3, 0],
     "decoder":["value_from_hex_data", "manufacturerdata", 6, 6, false, false],
     "post_proc":["%", 1000, "/", 10]
  },
  "_hum":{
     "condition":["manufacturerdata", 6, "bit", 3, 1],
     "decoder":["value_from_hex_data", "manufacturerdata", 6, 6, false, false],
     "post_proc":["-", 8388608, "%", 1000, "/", 10]
  },

But maybe there is a more elegant way to fix this.

Harald

[DigiH]

Hi @radioyear

Thanks for this info. I'm only on my phone until tomorrow evening, but could you try the following for the single existing humidity property

"hum":{
     "decoder":["value_from_hex_data", "manufacturerdata", 6, 6, false, false],
     "post_proc":["&", 8388607, "%", 1000, "/", 10]
  }, 

Which should mask the highest bit of the first byte to allow for the correct humidity with positive and negative temperatures.

Note to myself: The same fix needs to be applied to H5102

[radioyear]

Hi @DigiH,

I tried your solution and it's working. Humidity values are correct now with positiv and negative temperatures. Nice, thank you :)

Harald

[DigiH]

Thanks for the confirmation @radioyear !

I'll merge the fix(es) tomorrow night.

[DigiH]

Closing as the fix has been merged into development.

https://github.com/theengs/decoder/commit/0284e91bb8be4968cf3055810a055e76b9406de2