send last 2 bytes of mac as device id

CHANGELOG.md

@@ -10,6 +10,9 @@ and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0
 ### Added
 - Allow to request only the last X samples when doing a data download (implement Requested Samples Characterisitc on Download Service)
 
+### Fixed
+- use the last 2 Bytes of Mac Address as Device ID in BLE Advertisment (fixes mismatch of logged id and id appearing in MyAmbience as mentiond in https://github.com/Sensirion/arduino-ble-gadget/issues/44)
+
 ## [1.3.2] - 2024-06-19
 
 ### Fixed

src/AdvertisementHeader.cpp

@@ -12,6 +12,7 @@ void AdvertisementHeader::writeSampleType(uint8_t sampleType) {
     _writeByte(sampleType, 3);
 }
 
-void AdvertisementHeader::writeDeviceId(uint16_t deviceID) {
-    _write16BitBigEndian(deviceID, 4);
+void AdvertisementHeader::writeDeviceId(uint8_t deviceIDHigh, uint8_t deviceIDLow) {
+    _writeByte(deviceIDHigh, 4);
+    _writeByte(deviceIDLow, 5);
 }

src/AdvertisementHeader.h

@@ -40,7 +40,7 @@ class AdvertisementHeader: public ByteArray<ADVERTISEMENT_HEADER_SIZE_BYTES> {
     void writeCompanyId(uint16_t companyID);
     void writeSensirionAdvertisementType(uint8_t advType);
     void writeSampleType(uint8_t sampleType);
-    void writeDeviceId(uint16_t deviceID);
+    void writeDeviceId(uint8_t deviceIDHigh, uint8_t deviceIDLow);
 };
 
 #endif /* _ADVERTISEMENT_HEADER_H_ */

src/DataProvider.cpp

@@ -13,7 +13,9 @@ void DataProvider::begin() {
     // Use part of MAC address as device id
     std::string macAddress = _BLELibrary.getDeviceAddress();
     _advertisementHeader.writeDeviceId(
-        strtol(macAddress.substr(12, 17).c_str(), NULL, 16));
+        static_cast<uint8_t>(strtol(macAddress.substr(12, 14).c_str(), NULL, 16)),
+        static_cast<uint8_t>(strtol(macAddress.substr(15, 17).c_str(), NULL, 16))
+    );
 
     _BLELibrary.setAdvertisingData(_buildAdvertisementData());
     _BLELibrary.startAdvertising();