Add BLE utils for conditional notifications

Introduced ble_utils.h/cpp with setAndNotifyOnChange to update BLE characteristics and notify only on value changes. Updated bms_service.cpp to use this utility for failure level and MOS state characteristics, reducing unnecessary BLE notifications. Also added notification properties and descriptors to relevant characteristics.

Author: zjwhitehead

inc/sp140/ble/ble_utils.h

@@ -0,0 +1,47 @@
+#ifndef INC_SP140_BLE_BLE_UTILS_H_
+#define INC_SP140_BLE_BLE_UTILS_H_
+
+#include <BLECharacteristic.h>
+
+// Forward declare deviceConnected from ble.h
+extern bool deviceConnected;
+
+/**
+ * Sets a BLE characteristic value and conditionally notifies only when the value changes.
+ * Returns true if the value changed and a notification was sent, false otherwise.
+ *
+ * @param characteristic The BLE characteristic to update
+ * @param newValue The new value to set
+ * @param lastValue Reference to the variable tracking the previous value
+ * @return true if value changed and notification sent, false if no change
+ */
+template<typename T>
+bool setAndNotifyOnChange(BLECharacteristic* characteristic, T newValue, T& lastValue) {
+  if (characteristic == nullptr) {
+    return false;
+  }
+
+  characteristic->setValue(newValue);
+
+  if (newValue != lastValue) {
+    lastValue = newValue;
+    if (deviceConnected) {
+      characteristic->notify();
+    }
+    return true;  // Value changed
+  }
+  return false;  // No change
+}
+
+/**
+ * Specialization for uint8_t that uses pointer-based setValue (for binary data).
+ * Returns true if the value changed and a notification was sent, false otherwise.
+ *
+ * @param characteristic The BLE characteristic to update
+ * @param newValue The new uint8_t value to set
+ * @param lastValue Reference to the variable tracking the previous value
+ * @return true if value changed and notification sent, false if no change
+ */
+bool setAndNotifyOnChange(BLECharacteristic* characteristic, uint8_t newValue, uint8_t& lastValue);
+
+#endif  // INC_SP140_BLE_BLE_UTILS_H_

src/sp140/ble/ble_utils.cpp

@@ -0,0 +1,21 @@
+#include "sp140/ble/ble_utils.h"
+
+/**
+ * Specialization for uint8_t that uses pointer-based setValue (for binary data).
+ */
+bool setAndNotifyOnChange(BLECharacteristic* characteristic, uint8_t newValue, uint8_t& lastValue) {
+  if (characteristic == nullptr) {
+    return false;
+  }
+
+  characteristic->setValue(&newValue, sizeof(newValue));
+
+  if (newValue != lastValue) {
+    lastValue = newValue;
+    if (deviceConnected) {
+      characteristic->notify();
+    }
+    return true;  // Value changed
+  }
+  return false;  // No change
+}

src/sp140/ble/bms_service.cpp

@@ -4,6 +4,7 @@
 
 #include "sp140/ble.h"
 #include "sp140/ble/ble_ids.h"
+#include "sp140/ble/ble_utils.h"
 
 namespace {
 
@@ -22,6 +23,11 @@ BLECharacteristic* pBMSCellVoltages = nullptr;
 BLECharacteristic* pBMSChargeMos = nullptr;
 BLECharacteristic* pBMSDischargeMos = nullptr;
 
+// Track previous values to only notify on change
+uint8_t lastFailureLevel = 0;
+uint8_t lastChargeMos = 0;
+uint8_t lastDischargeMos = 0;
+
 }  // namespace
 
 void initBmsBleService(BLEServer* server) {
@@ -57,7 +63,8 @@ void initBmsBleService(BLEServer* server) {
       BLEUUID(BMS_LOW_TEMP_UUID), BLECharacteristic::PROPERTY_READ);
 
   pBMSFailureLevel = pBmsService->createCharacteristic(
-      BLEUUID(BMS_FAILURE_LEVEL_UUID), BLECharacteristic::PROPERTY_READ);
+      BLEUUID(BMS_FAILURE_LEVEL_UUID), BLECharacteristic::PROPERTY_READ | BLECharacteristic::PROPERTY_NOTIFY);
+  pBMSFailureLevel->addDescriptor(new BLE2902());
 
   pBMSVoltageDiff = pBmsService->createCharacteristic(
       BLEUUID(BMS_VOLTAGE_DIFF_UUID), BLECharacteristic::PROPERTY_READ);
@@ -66,10 +73,12 @@ void initBmsBleService(BLEServer* server) {
       BLEUUID(BMS_CELL_VOLTAGES_UUID), BLECharacteristic::PROPERTY_READ);
 
   pBMSChargeMos = pBmsService->createCharacteristic(
-      BLEUUID(BMS_CHARGE_MOS_UUID), BLECharacteristic::PROPERTY_READ);
+      BLEUUID(BMS_CHARGE_MOS_UUID), BLECharacteristic::PROPERTY_READ | BLECharacteristic::PROPERTY_NOTIFY);
+  pBMSChargeMos->addDescriptor(new BLE2902());
 
   pBMSDischargeMos = pBmsService->createCharacteristic(
-      BLEUUID(BMS_DISCHARGE_MOS_UUID), BLECharacteristic::PROPERTY_READ);
+      BLEUUID(BMS_DISCHARGE_MOS_UUID), BLECharacteristic::PROPERTY_READ | BLECharacteristic::PROPERTY_NOTIFY);
+  pBMSDischargeMos->addDescriptor(new BLE2902());
 
   // Ensure characteristics have deterministic startup values.
   uint16_t initial_cell_values[BMS_CELLS_NUM] = {0};
@@ -107,22 +116,8 @@ void updateBMSTelemetry(const STR_BMS_TELEMETRY_140& telemetry) {
   if (pBMSLowCell) pBMSLowCell->setValue(lowCell);
   if (pBMSHighTemp) pBMSHighTemp->setValue(highTemp);
   if (pBMSLowTemp) pBMSLowTemp->setValue(lowTemp);
-  if (pBMSFailureLevel) {
-    uint8_t failureLevel = telemetry.battery_failure_level;
-    pBMSFailureLevel->setValue(&failureLevel, sizeof(failureLevel));
-  }
   if (pBMSVoltageDiff) pBMSVoltageDiff->setValue(voltageDiff);
 
-  if (pBMSChargeMos) {
-    uint8_t chargeMos = telemetry.is_charge_mos ? 1 : 0;
-    pBMSChargeMos->setValue(&chargeMos, sizeof(chargeMos));
-  }
-
-  if (pBMSDischargeMos) {
-    uint8_t dischargeMos = telemetry.is_discharge_mos ? 1 : 0;
-    pBMSDischargeMos->setValue(&dischargeMos, sizeof(dischargeMos));
-  }
-
   if (pBMSCellVoltages) {
     uint16_t cell_millivolts[BMS_CELLS_NUM];
     for (uint8_t i = 0; i < BMS_CELLS_NUM; i++) {
@@ -133,6 +128,11 @@ void updateBMSTelemetry(const STR_BMS_TELEMETRY_140& telemetry) {
         BMS_CELLS_NUM * sizeof(uint16_t));
   }
 
+  // Handle state-change characteristics - only notify on change
+  setAndNotifyOnChange(pBMSFailureLevel, telemetry.battery_failure_level, lastFailureLevel);
+  setAndNotifyOnChange(pBMSChargeMos, static_cast<uint8_t>(telemetry.is_charge_mos ? 1 : 0), lastChargeMos);
+  setAndNotifyOnChange(pBMSDischargeMos, static_cast<uint8_t>(telemetry.is_discharge_mos ? 1 : 0), lastDischargeMos);
+
   if (!deviceConnected) {
     return;  // No notifications needed without a subscriber.
   }
@@ -145,8 +145,6 @@ void updateBMSTelemetry(const STR_BMS_TELEMETRY_140& telemetry) {
   if (pBMSLowCell) pBMSLowCell->notify();
   if (pBMSHighTemp) pBMSHighTemp->notify();
   if (pBMSLowTemp) pBMSLowTemp->notify();
-  if (pBMSFailureLevel) pBMSFailureLevel->notify();
   if (pBMSVoltageDiff) pBMSVoltageDiff->notify();
-  if (pBMSChargeMos) pBMSChargeMos->notify();
-  if (pBMSDischargeMos) pBMSDischargeMos->notify();
+  // Note: pBMSFailureLevel, pBMSChargeMos, pBMSDischargeMos notify separately above, only on change
 }

src/sp140/ble/config_service.cpp

@@ -12,6 +12,7 @@
 
 #include "sp140/ble.h"
 #include "sp140/ble/ble_ids.h"
+#include "sp140/ble/ble_utils.h"
 #include "sp140/device_state.h"
 #include "sp140/globals.h"
 #include "sp140/throttle.h"