Improve UI event protocol

The original protocol stores an entire array of UI event state of each control. This can easily exceed the 23 byte MTU limitation of GATT. To accomodate more controls, we:

 - add an GATT attribute for protocol version check
 - set protocol version to 2
 - replace the "event array" into a single event structure
 - the event structure contains "control index" and event info. This means we can only process 1 control event at a time

middleware/third_party/arduino/hardware/arduino/mt7697/libraries/LRemote/src/LRemote.cpp

@@ -28,7 +28,7 @@ static LBLECharacteristicString
                                                      // separated by the \n
                                                      // ASCII character
 static LBLECharacteristicBuffer
-    rcEventArray("b5d2ff7b-6eff-4fb5-9b72-6b9cff5181e7"); // Array of UINT8[4],
+    rcEvent("b5d2ff7b-6eff-4fb5-9b72-6b9cff5181e7"); // Array of UINT8[4],
                                                           // (sequence, event,
                                                           //  event data_byte1,
                                                           //  event data_byte2,
@@ -39,6 +39,8 @@ static LBLECharacteristicBuffer
 static LBLECharacteristicInt rcOrientation(
     "203fbbcd-9967-4eba-b0ff-0f72e5a634eb"); // 0: portrait, 1: landscape
 
+static LBLECharacteristicInt rcProtocolVersion("ae73266e-65d4-4023-8868-88b070d5d576"); // Incremental
+
 void LRemoteClass::begin() {
   // Initialize BLE subsystem if necessary
   initBLEOnce();
@@ -61,6 +63,7 @@ void LRemoteClass::begin() {
 
   // Set default values
   const size_t count = m_controls.size();
+  rcProtocolVersion.setValue(PROTOCOL_VERSION);
   rcControlCount.setValue(count);
   rcCol.setValue(m_canvasColumn);
   rcRow.setValue(m_canvasRow);
@@ -75,8 +78,12 @@ void LRemoteClass::begin() {
   LBLEValueBuffer frameArray;
   frameArray.resize(count * 4); // (x, y, r, c) are 4 uint8_t
 
-  LBLEValueBuffer eventArray;
-  eventArray.resize(count * 4);
+  RCEventInfo eventInfo;
+  eventInfo.seq = 0;
+  eventInfo.controlIndex = 0;
+  eventInfo.event = 0;
+  eventInfo.processedSeq = 0;
+  eventInfo.data = 0;
 
   String nameList;
 
@@ -96,12 +103,6 @@ void LRemoteClass::begin() {
     nameList += m_controls[i]->m_text;
     nameList += '\n';
 
-    // convert default values of each control to BLE attribute
-    const RCEventInfo &info = m_controls[i]->m_lastEvent;
-    eventArray[i * 4 + 0] = 0;                         // initial sequence = 0
-    eventArray[i * 4 + 1] = 0;                         // initial event = 0
-    *((uint16_t *)&eventArray[i * 4 + 2]) = info.data; // initial data
-
     Serial.println("config data fill");
     // fill the additional config data
     RCConfigData configData;
@@ -113,7 +114,7 @@ void LRemoteClass::begin() {
   rcColors.setValueBuffer(&colorArray[0], colorArray.size());
   rcFrames.setValueBuffer(&frameArray[0], frameArray.size());
   rcNames.setValue(nameList);
-  rcEventArray.setValueBuffer(&eventArray[0], eventArray.size());
+  rcEvent.setValueBuffer((uint8_t*)&eventInfo, sizeof(eventInfo));
   rcConfigDataArray.setValueBuffer(&configDataArray[0], configDataArray.size());
 
   initPeripheralOnce();
@@ -136,14 +137,15 @@ void LRemoteClass::initBLEOnce() {
   }
 
   // Add characteristics into rcService
+  rcService.addAttribute(rcProtocolVersion);
   rcService.addAttribute(rcCol);
   rcService.addAttribute(rcRow);
   rcService.addAttribute(rcControlCount);
   rcService.addAttribute(rcControlTypes);
   rcService.addAttribute(rcColors);
   rcService.addAttribute(rcFrames);
   rcService.addAttribute(rcNames);
-  rcService.addAttribute(rcEventArray);
+  rcService.addAttribute(rcEvent);
   rcService.addAttribute(rcConfigDataArray);
   rcService.addAttribute(rcOrientation);
 
@@ -167,18 +169,25 @@ bool LRemoteClass::connected() { return LBLEPeripheral.connected(); }
 
 void LRemoteClass::process() {
   // check if new event coming in
-  if (rcEventArray.isWritten()) {
-    const LBLECharacteristicWrittenInfo &written =
-        rcEventArray.getLastWrittenInfo();
+  if (rcEvent.isWritten()) {
+    const LBLECharacteristicWrittenInfo &written = rcEvent.getLastWrittenInfo();
+
+    RCEventInfo event = {0};
 
-    // scan and compare for event serial numbers
-    for (size_t i = 0; i < m_controls.size(); i++) {
+    // retrieve the control's event info
+    rcEvent.getValue((uint8_t *)&event, sizeof(event), 0);
 
+    // scan and update event info
+    // make sure that the "sequence number" is incremented
+    // (and thus different from the control's record)
+    const size_t i = event.controlIndex;
       LRemoteUIControl &control = *m_controls[i];
+    const uint8_t oldSeq = control.m_lastEvent.seq;
+    control.m_lastEvent = event;
+    control.m_lastEvent.seq = oldSeq + 1;
 
-      // retrieve the control's event info
-      rcEventArray.getValue((uint8_t *)&control.m_lastEvent, 4, i * 4);
-    }
+    event.processedSeq = event.seq;
+    rcEvent.setValueBuffer((uint8_t *)&event, sizeof(event));
   }
 }
 

middleware/third_party/arduino/hardware/arduino/mt7697/libraries/LRemote/src/LRemote.h

@@ -4,6 +4,8 @@
 #include <LBLEPeriphral.h>
 #include <vector>
 
+#define PROTOCOL_VERSION (2)
+
 // Background / primary color of the UI control
 enum RCColorType {
   RC_ORANGE = 1,
@@ -35,9 +37,11 @@ enum RCControlType {
 
 // Internal data structure for BLE events
 struct RCEventInfo {
-  uint8_t seq;
-  uint8_t event;
-  uint16_t data;
+  uint8_t seq;            // from Mobile, increment sequence serial number
+  uint8_t controlIndex;   // from Mobile, index into the control array of the event origin
+  uint8_t event;          // from Mobile, event type
+  uint8_t processedSeq;   // from Arduino, last processed serial number.
+  uint16_t data;          // from Mobile, data of the event
 };
 
 // Internal structure for storing config data.