xiaomi-thb.ino and temperature below 0

[fulvioalessio]

Hi, I've tested 1.2 Fw on my devices. Seems that esp32 code doesn't manage negative temperature.

Here .ino debug:

`[D][BLEAdvertisedDevice.cpp:247] parseAdvertisement(): Type: 0x16 (), length: 17, data: 1a181477c638c1a4fcffda1cd10a3f9d0d

[D][BLEAdvertisedDevice.cpp:247] parseAdvertisement(): Type: 0x09 (), length: 10, data: 4154435f433637373134

[D][BLEAdvertisedDevice.cpp:407] setName(): - setName(): name: ATC_C67714

Found service '181a' data len: 19, 12161a181477c638c1a4fcffda1cd10a3f9d0d

MAC: 5 Temp: 655.32°, Humidity: 73.86%, Vbatt: 2769, Battery: 63%, flg: 0x0d, cout: 157 FEED: MAC a4c138c67714 temp 655.320007 humidity 73.860001 bat 2769.000000

Found service '181a' data len: 19, 12161a181477c638c1a4f4ff041dcb0a3eaf0d

MAC: 5 Temp: 655.24°, Humidity: 74.28%, Vbatt: 2763, Battery: 62%, flg: 0x0d, cout: 175 FEED: MAC a4c138c67714 temp 655.239990 humidity 74.279999 bat 2763.000000 `

[tomcat-xx]

LYWSD03MMC is specified for temperatures above 0 only (0-60). So maybe it's not an issue of reading software. I have this for 3 different ways of accessing LYWSD03MMC data. On the other hand I often read about some python script as base of coding. So if there's an error maybe it is inherited to all other implementations.

[fulvioalessio]

Hi,

LYWSD03MMC can read temperature below 0. I think there is only a little issue in .ino source code. With atc1441 firmware I was able to display correct temperature. With new firmware I used .ino example to understand new data format and you can view the result.

[pvvx]

      float temp = *(int16_t*)(serviceData + 10) / 100.0;

https://github.com/pvvx/ATC_MiThermometer/commit/bb5c031d2816bca1818c2b01a63e1c472368e546

Sensor SHTV3/SHTC3: -40°C to 125°C.

20:20:39.725 -> Found service '181a' data len: 19, 12161a18a1cb7f38c1a4dbfdb00e8f0a37d80d
20:20:39.725 -> MAC: a4c1387fcba1
20:20:39.725 -> Temp: -5.49°, Humidity: 37.60%, Vbatt: 2703, Battery: 55%, flg: 0x0d, cout: 216

[tomcat-xx]

Great to hear (both answers above ;-)

[pvvx]

Advertising in 4 formats: https://github.com/pvvx/ATC_MiThermometer/blob/master/src/ble.h#L31-L88

// GATT Service 0x181A Environmental Sensing
// All data little-endian
typedef struct __attribute__((packed)) _adv_custom_t {
    uint8_t     size;   // = 19
    uint8_t     uid;    // = 0x16, 16-bit UUID
    uint16_t    UUID;   // = 0x181A, GATT Service 0x181A Environmental Sensing
    uint8_t     MAC[6]; // [0] - lo, .. [6] - hi digits
    int16_t     temperature; // x 0.1 degree
    uint16_t    humidity; // x 0.01 %
    uint16_t    battery_mv; // mV
    uint8_t     battery_level; // 0..100 %
    uint8_t     counter; // measurement count
    uint8_t     flags; 
} adv_custom_t, * padv_custom_t;

// GATT Service 0x181A Environmental Sensing
// mixture of little-endian and big-endian!
typedef struct __attribute__((packed)) _adv_atc1441_t {
    uint8_t     size;   // = 16
    uint8_t     uid;    // = 0x16, 16-bit UUID
    uint16_t    UUID;   // = 0x181A, GATT Service 0x181A Environmental Sensing (little-endian)
    uint8_t     MAC[6]; // [0] - hi, .. [6] - lo digits (big-endian!)
    uint8_t     temperature[2]; // x 0.1 degree (big-endian!)
    uint8_t     humidity; // x 1 %
    uint8_t     battery_level; // 0..100 %
    uint8_t     battery_mv[2]; // mV (big-endian!)
    uint8_t     counter; // measurement count
} adv_atc1441_t, * padv_atc1441_t;

// UUID for Members 0xFE95 Xiaomi Inc. https://btprodspecificationrefs.blob.core.windows.net/assigned-values/16-bit%20UUID%20Numbers%20Document.pdf
// All data little-endian, + https://github.com/Magalex2x14/LYWSD03MMC-info
typedef struct __attribute__((packed)) _adv_mi_t {
    uint8_t     size;   // = 21
    uint8_t     uid;    // = 0x16, 16-bit UUID https://www.bluetooth.com/specifications/assigned-numbers/generic-access-profile/
    uint16_t    UUID;   // = 0xFE95, 16-bit UUID for Members 0xFE95 Xiaomi Inc.
    uint16_t    ctrl;   // = 0x3050 Frame ctrl
    uint16_t    dev_id; // = 0x055B Device type
    uint8_t     counter; // 0..0xff..0 measurement count
    uint8_t     MAC[6]; // [0] - lo, .. [6] - hi digits
    // +15: 0x0A, 0x10, 0x01, t_lv, 0x02, b_lo, b_hi
    // +15: 0x0D, 0x10, 0x04, t_lo, t_hi, h_lo, h_hi
    uint8_t     data_id;    // = 0x0A or 0x0D
    uint8_t     nx10;       // = 0x10
    union {
        struct {
            uint8_t     len1; // = 0x01
            uint8_t     battery_level; // 0..100 %
            uint8_t     len2; // = 0x02
            uint16_t    battery_mv;
        }t0a;
        struct {
            uint8_t     len; // = 0x04
            int16_t     temperature; // x0.1 C
            uint16_t    humidity; // x0.1 %
        }t0d;
    };
} adv_mi_t, * padv_mi_t;

[pvvx]