These units do work with negative (freezing) temps, correct decoding algorithm

[eharris]

I tested with a unit and have verified that these do work and read negative temps. According to their marketing materials, they only claim the device supports 0-50 degrees C, but the mobile app shows the range as -20C to 60C. I have personally verified that my unit reads sub-freezing temps (although I didn't have a way to test all the way down to -20C).

The decoding algorithm description could use updating to be less complicated and more accurate. Converting to a binary string isn't needed. The algorithm I used is (pseudocode):

Join the 3 data bytes together and convert to an integer, then:

if (val & 0x800000) {
    is_negative = true;
    val = val ^ 0x800000;
}
humidity = (val % 1000) / 10;
temp = int(val / 1000) / 10;
if (is_negative) {
    temp = 0 - temp;
}
# If desire Farenheit
temp = temp * 9 / 5 + 32;

[Thrilleratplay]

The official operating temperature range, according to Govee, for the H5075 is 0°C - 50°C (32°F - 122°F). It may display and send negative temperatures but I would be suspicious of those values. Also standard LCDs do not do well in freezing temperatures.

[JZ-SmartThings]

I see that there has bee some discussion about negative temperature... the below seems to work for me and reports pretty accurately in tests with my fridge & freezer...

    - lambda: |-
        for (auto data : x.get_manufacturer_datas()) {
            if(data.data.size()==6) {
              const int basenum = (int16_t(data.data[1]) << 16) + (int16_t(data.data[2]) << 8) + int16_t(data.data[3]);
              float temperature = (basenum / 10000.0f);
              ESP_LOGD("custom", "Govee Two Reported Temp: %f", temperature);
              if(temperature>=839.0) {
                temperature = temperature-839;
                temperature = -temperature * 9.0/5.0 + 32.0;
              } else {
                temperature = temperature * 9.0/5.0 + 32.0;
              }
           }