BLE api 将负温度转换为正温度

Question

我想使用 ESP32 芯片从 BLE 信标中提取温度。我使用以下代码来执行此操作：

class MyAdvertisedDeviceCallbacks: public BLEAdvertisedDeviceCallbacks {

void onResult(BLEAdvertisedDevice advertisedDevice) {
  std::string strServiceData = advertisedDevice.getServiceData();
  uint8_t cServiceData[100];
  strServiceData.copy((char *)cServiceData, strServiceData.length(), 0);

  if (advertisedDevice.getServiceDataUUID().equals(BLEUUID(beconUUID))==true) // found Eddystone UUID
  {  
    Serial.printf("Advertised Device: %s \n", advertisedDevice.toString().c_str());advertisedDevice.getServiceDataUUID().bitSize(), advertisedDevice.getServiceDataUUID().toString().c_str(),strServiceData.length());

    if (cServiceData[0]==0x20) 
    {
       BLEEddystoneTLM oBeacon = BLEEddystoneTLM();
       oBeacon.setData(strServiceData);
       Serial.printf("Eddystone Frame Type (Unencrypted Eddystone-TLM) \n");
       Serial.printf(oBeacon.toString().c_str());
    } 
    else 
    {
      
    }
   } 
  }
};

void setup() {
 Serial.begin(115200);

 BLEDevice::init("");
 pBLEScan = BLEDevice::getScan(); //create new scan
 pBLEScan->setAdvertisedDeviceCallbacks(new MyAdvertisedDeviceCallbacks());
 pBLEScan->setActiveScan(true); //active scan uses more power, but get results faster
}

void loop() {
 BLEScanResults foundDevices = pBLEScan->start(scanTime);
 delay(5000);
}

正值的温度输出很好，但是当温度变为负值时，我仍然得到一个异常的正数。

串行监视器输出：

Advertised Device: Name: , Address: ac:23:3f:85:2e:f3, serviceUUID: 0000feaa-0000-1000-8000-00805f9b34fb 
Eddystone Frame Type (Unencrypted Eddystone-TLM) 
Version 
art_cpu0_default mV
Temperature 241.0 °C
Adv. Count 3782
Time 0000.00:30:34

从上面的调试消息中，这个特定的信标应该读取 -18 C 而不是 235.0 C。我知道这是因为 BLE 标签附带的 android 应用程序显示温度为 -18 C然后我将标签放入设置为 -18 C 的冰箱中。

任何人都可以帮助我，为什么我得到的浮点值应该是负的？

可以找到我正在使用的库here

根据用户的建议，我注意到我的问题不在于我的代码，而在于库。代码太长 post 但是上面提供了 link。问题似乎与 m_eddystoneData.temp 的声明和将 temp 转换为无符号值有关。因此输出将始终为正。

void BLEEddystoneTLM::setTemp(float temp) {
  m_eddystoneData.temp = (uint16_t)temp;
} // setTemp

Answer 1

我查看了您链接到的库，其中包含以下温度信息：

void BLEEddystoneTLM::setTemp(float temp) {
    m_eddystoneData.temp = (uint16_t)temp;
} // setTemp

和

BLEEddystoneTLM::BLEEddystoneTLM() {
    beaconUUID = 0xFEAA;
    m_eddystoneData.frameType = EDDYSTONE_TLM_FRAME_TYPE;
    m_eddystoneData.version = 0;
    m_eddystoneData.volt = 3300; // 3300mV = 3.3V
    m_eddystoneData.temp = (uint16_t) ((float) 23.00);
    m_eddystoneData.advCount = 0;
    m_eddystoneData.tmil = 0;
} // BLEEddystoneTLM

两者似乎都将温度定义为 16 位的无符号短整数。我认为他们应该签名，因此 int16_t

BLE api 将负温度转换为正温度

BLE api converts negative temperature to positive

c++

floating-point

arduino

bluetooth-lowenergy