From e0993f18a144db63e7a1b7c5d4c537f6d82957ec Mon Sep 17 00:00:00 2001
From: lfierz <leonie.fierz@sensirion.com>
Date: Tue, 22 Oct 2024 15:28:42 +0200
Subject: [PATCH] send last 2 bytes of mac as device id

instead of only sending the last byte
this fixes mismatch of logged device id on Serial output
of the ESP and device id which appears in MyAmbience (as mentioned in issue #44
---
 CHANGELOG.md                | 3 +++
 src/AdvertisementHeader.cpp | 5 +++--
 src/AdvertisementHeader.h   | 2 +-
 src/DataProvider.cpp        | 4 +++-
 4 files changed, 10 insertions(+), 4 deletions(-)

diff --git a/CHANGELOG.md b/CHANGELOG.md
index 891f1bd..4e7a024 100644
--- a/CHANGELOG.md
+++ b/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
diff --git a/src/AdvertisementHeader.cpp b/src/AdvertisementHeader.cpp
index 7d83faf..793280e 100644
--- a/src/AdvertisementHeader.cpp
+++ b/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);
 }
diff --git a/src/AdvertisementHeader.h b/src/AdvertisementHeader.h
index 97f0380..217c859 100644
--- a/src/AdvertisementHeader.h
+++ b/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_ */
\ No newline at end of file
diff --git a/src/DataProvider.cpp b/src/DataProvider.cpp
index c8eef9d..382361e 100644
--- a/src/DataProvider.cpp
+++ b/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();