【FireBeetle 2 ESP32 C6开发板】-3- C6获取小米温湿度计2数据

慕容雪花 发表于 2024-5-1 11:12

本帖最后由慕容雪花于 2024-5-2 12:36 编辑

小米温湿度计2 是从设备，同时也是BLE SERVER，部署了多个sevice，其中serviceUUID("ebe0ccb0-7a0a-4b0c-8a1a-6ff2997da3a6")里面的charUUID("ebe0ccc1-7a0a-4b0c-8a1a-6ff2997da3a6")就是温湿度数据。

 

esp32c6是主设备，同时也是BLE CLIENT，通过BLE的协议来访问Server上的Characteristic，从而获取到温湿度数据。

C6启动后，会开始扫描周围的BLE设备，此时进行一个判断，设备名称是否为XiaomiDeviceName = "LYWSD03MMC"

<pre>
<code> /**
* Called for each advertising BLE server.
*/
void onResult(BLEAdvertisedDevice advertisedDevice) {
Serial.println("*-------------------------------------------------------------------*");
Serial.print("BLE Advertised Device found: ");
Serial.println(advertisedDevice.toString().c_str());

// We have found a device, let us now see if it contains the service we are looking for.

Serial.println(advertisedDevice.getServiceUUID().toString().c_str());
Serial.println(advertisedDevice.getName().c_str());

if(0 == advertisedDevice.getName().compareTo(XiaomiDeviceName)){
 Serial.println("Great, Found " + advertisedDevice.getName());

 Serial.println("advertisedDevice.getServiceUUIDCount() = " + String(advertisedDevice.getServiceUUIDCount()));

 BLEDevice::getScan()->stop();
 myDevice = new BLEAdvertisedDevice(advertisedDevice);
 doConnect = true;
 doScan = true;
}
} // onResult</code></pre>

找到小米设备后，进行连接：

<pre>
<code>bool connectToServer() {
Serial.print("Forming a connection to ");
Serial.println(myDevice->getAddress().toString().c_str());

BLEClient*pClient= BLEDevice::createClient();
Serial.println(" - Created client");

pClient->setClientCallbacks(new MyClientCallback());

// Connect to the remove BLE Server.
pClient->connect(myDevice);// if you pass BLEAdvertisedDevice instead of address, it will be recognized type of peer device address (public or private)
Serial.println(" - Connected to server");
pClient->setMTU(517); //set client to request maximum MTU from server (default is 23 otherwise)

// Obtain a reference to the service we are after in the remote BLE server.
BLERemoteService* pRemoteService = pClient->getService(serviceUUID);
if (pRemoteService == nullptr) {
 Serial.print("Failed to find our service UUID: ");
 Serial.println(serviceUUID.toString().c_str());
 pClient->disconnect();
 return false;
}
Serial.println(" - Found our service");

// Obtain a reference to the characteristic in the service of the remote BLE server.
pRemoteCharacteristic = pRemoteService->getCharacteristic(charUUID);
if (pRemoteCharacteristic == nullptr) {
 Serial.print("Failed to find our characteristic UUID: ");
 Serial.println(charUUID.toString().c_str());
 pClient->disconnect();
 return false;
}
Serial.println(" - Found our characteristic");

// Read the value of the characteristic.
if(pRemoteCharacteristic->canRead()) {
 String value = pRemoteCharacteristic->readValue();
 Serial.print("The characteristic value was: ");
 Serial.println(value.c_str());
}

if(pRemoteCharacteristic->canNotify())
 pRemoteCharacteristic->registerForNotify(notifyCallback);

connected = true;
return true;
}</code></pre>

从小米设备获取到数据，共有5个字节。

<pre>
<code>static void notifyCallback(
BLERemoteCharacteristic* pBLERemoteCharacteristic,
uint8_t* pData,
size_t length,
bool isNotify) {
Serial.print("Notify callback for characteristic ");
Serial.print(pBLERemoteCharacteristic->getUUID().toString().c_str());
Serial.print(" of data length ");
Serial.println(length);

uint16_t TempVal = pData*256 + pData;
Serial.println("Temperature is: "+ String(TempVal/100) + "." + String(TempVal%100) + " degree");

uint8_t HumidityVal = pData;
Serial.println("Humidity is: " + String(pData) + "% ");

uint16_t BatteryVal = pData*256 + pData;
Serial.println("Battery Voltage is: "+ String(BatteryVal/100) + "." + String(BatteryVal%100) + " mV");

Serial.println();
}</code></pre>

注意数据为小端模式存储。

 

  

-------------------------------------------------------------------------------------------------------------------

5.2日更新：

上文中BLE SERVER notify上来的数据是没有问题的，温湿度值跟实际设备对比也是OK的，但是仔细观察设备启动，首次连接小米设备成功后，直接读取Characteristic的值，竟然是4？？

  

这个肯定是读取的姿势不对，我接下来一番笨丁解牛。

小米温湿度数据格式为：F2 07 4A C3 0A。也就是5个十六进制数据。仔细看当前的直接读取Characteristic值代码：

<pre>
<code> // Read the value of the characteristic.
if(pRemoteCharacteristic->canRead()) {
 String value = pRemoteCharacteristic->readValue();
 Serial.print("The characteristic value was: ");
 Serial.println(value.c_str());
}</code></pre>

readValue()方法返回的是String类型变量，更合适的应该是：

<pre>
<code>uint8_t* test = pRemoteCharacteristic->readRawData();</code></pre>

  

计算一下使用直接读取数据所对应的温湿度：

  

 

代码：

<pre>
<code>uint8_t* test = pRemoteCharacteristic->readRawData();
 uint8_t i;
 uint8_ttest_temp_val={0};

 for(i = 0; i < 5; i++){
 if(test != nullptr){
 Serial.print("The characteristic value using readRawData was: ");
 Serial.println(*test);
 test_temp_val = *test;
 }else{
 Serial.println("pRemoteCharacteristic->readRawData() returns NULL PTR");
 }
 test++;
 }

static uint16_t Test_TempVal = test_temp_val*256 + test_temp_val;
Serial.println("Test Temperature is: "+ String(Test_TempVal/100) + "." + String(Test_TempVal%100) + " degree");

static uint8_t Test_HumidityVal = test_temp_val;
Serial.println("Test Humidity is: " + String(test_temp_val) + "% ");

static uint16_t Test_BatteryVal = test_temp_val*256 + test_temp_val;
Serial.println("Test Battery Voltage is: "+ String(Test_BatteryVal/100) + "." + String(Test_BatteryVal%100) + " mV");
</code></pre>

参考：

读取小米蓝牙温湿度计2数据 <a href="https://www.cnblogs.com/qsbye/p/15913753.html" target="_blank">https://www.cnblogs.com/qsbye/p/15913753.html</a>

chejm 发表于 2024-5-1 17:49

感谢楼主分享的技术内容，有机会一定买块板子动手测试一下这些例子

lugl4313820 发表于 2024-5-1 22:49

C6启动后，会开始扫描周围的BLE设备，此时进行一个判断，设备名称是否为XiaomiDeviceName = "LYWSD03MMC"

不会吧，直接可以读出小米的东西吗？

慕容雪花 发表于 2024-5-2 08:52

lugl4313820 发表于 2024-5-1 22:49
C6启动后，会开始扫描周围的BLE设备，此时进行一个判断，设备名称是否为XiaomiDeviceName = "LYWSD03MMC ...

可以的大佬，是我太菜了。我尝试扫描周围设备，想直接根据SERVICE UUID来锁定小米温湿度度计2，但可能小米设备的广播报文里面并没有包含serviceUUID("ebe0ccb0-7a0a-4b0c-8a1a-6ff2997da3a6")。所以才直接根据设备名称来锁定小米设备。

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【FireBeetle 2 ESP32 C6开发板】-3- C6获取小米温湿度计2数据