[Linkit7697] BLE SimplePeripheral 範例研究

最近剛出爐的7697，具有BLE功能，SimplePeripheral範例中使用BLE點亮LED，在範例目錄…\Arduino15\packages\LinkIt\hardware\linkit_rtos\0.7.11\libraries\LBLE\examples\SimplePeripheral之下有個aia檔，它用了實驗性的Bluetooth LE extension，匯入AppInventor後的畫面如下：

SimplePeripheral只用到INT類型的characteristic來控制LED，寫入1時點亮，寫入0時熄滅，在Android系統可以使用BLE Scanner或BLE UUID Explorer等App軟體來測試。其實閱讀…l\Arduino15\packages\LinkIt\hardware\linkit_rtos\0.7.11\libraries\LBLE\src之程式碼可以發現，7697還有支援字串類型的characteristic，不過因為BLE的封包很短，扣除掉一些header後，在android系統每個封包最多只能傳送20 bytes。如果想用字串來傳遞WiFi AP的ssid與password，除非自行切割長字串，不然也只能使用20 bytes的ssid與密碼。下面這個程式加入了字串類型的characteristic，當使用App對characteristic進行寫入之後，7697的LBLEPeriphral.cpp會自動保存其寫入的資料，之後可用Characteristic.isWritten()判斷而將寫入的資料取出。使用BLE UUID Explorer的操作畫面，掃描裝置結果如下圖：

 點選裝置後，點開Unknown service後可看到3個characteristic，畫面如下圖：

第一個Unknown characteristic是INT類型，點選進入讀寫畫面，寫入1後，7697上的LED就會點亮，這跟用AppInventor程式的效果相同，畫面如下圖：

第2個或第3個Unknown characteristic是String類型，寫入字串後再按Read讀回，證明7697的確有將資料保存起來的，畫面如下圖：

 此時在Arduino終端機上可以見到輸入的字串，畫面如下圖：

程式碼如下

#include <LBLE.h> #include <LBLEPeriphral.h> // Define a simple GATT service with only 1 characteristic LBLEService nodeService("19B10010-E8F2-537E-4F6C-D104768A1214"); LBLECharacteristicInt switchCharacteristic("19B10011-E8F2-537E-4F6C-D104768A1214", LBLE_READ | LBLE_WRITE); LBLECharacteristicString ssidCharacteristic("19B10012-E8F2-537E-4F6C-D104768A1214", LBLE_READ | LBLE_WRITE); LBLECharacteristicString passCharacteristic("19B10013-E8F2-537E-4F6C-D104768A1214", LBLE_READ | LBLE_WRITE); String ssid="ssid"; String pass="pass"; void setup() {   // Initialize LED pin   pinMode(LED_BUILTIN, OUTPUT);   digitalWrite(LED_BUILTIN, LOW);   //Initialize serial and wait for port to open:   Serial.begin(9600);   Serial.println("node begin");   // Initialize BLE subsystem   LBLE.begin();   while (!LBLE.ready()) {     delay(100);     Serial.print(".");   }    Serial.println("BLE ready");   Serial.print("Device Address = [");   Serial.print(LBLE.getDeviceAddress());   Serial.println("]");   // configure our advertisement data.   // In this case, we simply create an advertisement that represents an   // connectable device with a device name   LBLEAdvertisementData advertisement;   advertisement.configAsConnectableDevice("BLE LED");   // Configure our device's Generic Access Profile's device name   // Ususally this is the same as the name in the advertisement data.   LBLEPeripheral.setName("BLE LED");   // Add characteristics into ledService   nodeService.addAttribute(switchCharacteristic);   nodeService.addAttribute(ssidCharacteristic);   nodeService.addAttribute(passCharacteristic);   // Add service to GATT server (peripheral)   LBLEPeripheral.addService(nodeService);   // start the GATT server - it is now   // available to connect   LBLEPeripheral.begin();   // start advertisment   LBLEPeripheral.advertise(advertisement); } void loop() {   delay(100);   if (switchCharacteristic.isWritten()) {     const char value = switchCharacteristic.getValue();     switch (value) {       case 1:         digitalWrite(LED_BUILTIN, HIGH);         break;       case 0:         digitalWrite(LED_BUILTIN, LOW);         break;       default:         Serial.println("Unknown value written");         break;     }   }   if (ssidCharacteristic.isWritten()) {         ssid = ssidCharacteristic.getValue();         Serial.print("ssid="); Serial.println(ssid);   }   if (passCharacteristic.isWritten()) {         pass = ssidCharacteristic.getValue();         Serial.print("pass="); Serial.println(pass);   } }