Adding basic BLE Notify example for sending GPS data

bolt-ons/gps-bolt-on/GPS_BLE_Notify.ino

@@ -0,0 +1,294 @@
+#include <TinyGPSPlus.h>
+
+/*
+  Heavily based on the example BLE notify code provided with ESP32 on Arduino IDE. 
+  Great video that goes over BLE concepts with ESP32: https://youtu.be/0Yvd_k0hbVs?si=qxlBrfBaO1deO5Bh 
+
+  This basic example will create a BLE notify server and send updates everytime the GPS module updates.
+  A 32 byte payload is created and transfered on each GPS update
+    - bytes 0-7 latitude
+    - bytes 8-15 longitude
+    - bytes 16-23 speed m/s 
+    - bytes 24-25 year
+    - bytes 26 month
+    - bytes 27 day 
+    - bytes 28 hours
+    - bytes 29 minute
+    - bytes 30 second
+    - bytes 31 centisecond
+
+    **Pin Configuration:**  
+    - Rx to GPS module (tx from ESP32) - pin 17 of SV1 - GPIO40 of ESP32
+    - Tx from GPS module (rx to ESP32) - pin 18 of SV1 - GPIO41 of ESP32
+    - P1PPS from GPS module            - pin 16 of SV1 - GPIO39 of ESP32
+    - PSE_SEL from GPS moduel          - pin 11 of SV1 - GPIO45 of ESP32
+*/
+#include <BLEDevice.h>
+#include <BLEServer.h>
+#include <BLEUtils.h>
+#include <BLE2902.h>
+#include <BLE2901.h>
+#include <TinyGPS++.h>
+
+// Change to give device custom name that displays during GPS search
+String deviceName = "ASL ESP32 + GPS";
+
+// Change to whatever you'd like, good generator here: https://www.uuidgenerator.net 
+// UUIDs are required 
+#define SERVICE_UUID        "ECBB8159-FBA9-4123-AEF0-CA06E1D390D9"
+#define CHARACTERISTIC_UUID "beb5483e-36e1-4688-b7f5-ea07361b26a8"
+
+// GPS Settings 
+
+// Desired update rate in Hz (1,5, 10, 25, 50)
+static const uint8_t updateRateHz = 10;
+// Baud-rate code for 115200 is 5
+static const uint8_t baudCode115k = 5;
+
+
+BLEServer *pServer = NULL;
+BLECharacteristic *pCharacteristic = NULL;
+BLE2901 *descriptor_2901 = NULL;
+
+bool deviceConnected = false;
+bool oldDeviceConnected = false;
+
+// GPS parsing 
+TinyGPSPlus gps; 
+
+// type defs for packing gps data into bytes for ble
+union latBytes {
+  double lat;
+  uint8_t bytes[8];
+} latUnion; 
+
+union longBytes {
+  double lng;
+  uint8_t bytes[8];
+} longUnion; 
+
+union speedBytes {
+  double speed;
+  uint8_t bytes[8];
+} speedUnion; 
+
+union yearBytes {
+  int year;
+  uint8_t bytes[2];
+} yearUnion; 
+
+union monthBytes {
+  int month;
+  uint8_t bytes[1];
+} monthUnion; 
+
+union dayBytes {
+  int day;
+  uint8_t bytes[1];
+} dayUnion; 
+
+union hourBytes {
+  int hour;
+  uint8_t bytes[1];
+} hourUnion; 
+
+union minBytes {
+  int min;
+  uint8_t bytes[1];
+} minUnion; 
+
+union secBytes {
+  int sec;
+  uint8_t bytes[1];
+} secUnion; 
+
+union centBytes {
+  int cent;
+  uint8_t bytes[1];
+} centUnion; 
+
+void configureSkytraqUpdateRate(uint8_t rateHz) {
+  // Payload bytes: { MsgID=0x0E, Rate, Attributes=0 }
+  const uint8_t payloadLen = 3;
+  uint8_t payload[payloadLen] = { 0x0E, rateHz, 0x00 };
+
+  // XOR‐checksum over the payload bytes
+  uint8_t checksum = 0;
+  for (uint8_t i = 0; i < payloadLen; i++) {
+    checksum ^= payload[i];
+  }
+
+  // Build the full packet:
+  //  A0 A1 00 03 [payload…] [checksum] 0D 0A
+  uint8_t pkt[2 + 2 + payloadLen + 1 + 2] = {
+    0xA0, 0xA1,             // header
+    0x00, payloadLen,       // payload length MSB=0, LSB=3
+    payload[0], payload[1], payload[2], // payload
+    checksum,               // XOR of payload[]
+    0x0D, 0x0A              // terminator
+  };
+
+  Serial1.write(pkt, sizeof(pkt));
+}
+
+
+void configureSkytraqBaudRate(uint8_t baudCode) {
+  // Payload bytes: { MsgID=0x05, COM_port=0, BaudCode, Attributes=0 }
+  const uint8_t payloadLen = 4;
+  uint8_t payload[payloadLen] = { 0x05, 0x00, baudCode, 0x00 };
+
+  // XOR-checksum over the payload bytes
+  uint8_t checksum = 0;
+  for (uint8_t i = 0; i < payloadLen; i++) {
+    checksum ^= payload[i];
+  }
+
+  // Build the full packet:
+  //  A0 A1 00 04 [payload…] [checksum] 0D 0A
+  uint8_t pkt[2 + 2 + payloadLen + 1 + 2] = {
+    0xA0, 0xA1,             // header
+    0x00, payloadLen,       // payload length MSB=0, LSB=4
+    payload[0], payload[1], payload[2], payload[3], // payload
+    checksum,               // XOR of payload[]
+    0x0D, 0x0A              // terminator
+  };
+
+  Serial1.write(pkt, sizeof(pkt));
+}
+
+class MyServerCallbacks : public BLEServerCallbacks {
+  void onConnect(BLEServer *pServer) {
+    deviceConnected = true;
+  };
+
+  void onDisconnect(BLEServer *pServer) {
+    deviceConnected = false;
+  }
+};
+
+
+void setup() {
+  Serial.begin(9600);
+
+  // start reading from the gps module
+  Serial1.begin(9600, SERIAL_8N1, 41, 40); // Initialize serial communication with the GPS module
+  // Note: Replace 41 and 40 with actual RX and TX pins if required by your hardware.
+  configureSkytraqBaudRate(baudCode115k);
+  // give module a moment to switch
+  delay(1000);
+  Serial1.begin(115200);    
+  configureSkytraqUpdateRate(updateRateHz);
+  Serial.println("GPS Module Initialized");
+
+
+  BLEDevice::init(deviceName);
+
+  // Create the BLE Server
+  pServer = BLEDevice::createServer();
+  pServer->setCallbacks(new MyServerCallbacks());
+
+  // Create the BLE Service
+  BLEService *pService = pServer->createService(SERVICE_UUID);
+
+  // Create a BLE Characteristic
+  pCharacteristic = pService->createCharacteristic(
+    CHARACTERISTIC_UUID,
+    BLECharacteristic::PROPERTY_NOTIFY
+  );
+
+  // Creates BLE Descriptor 0x2902: Client Characteristic Configuration Descriptor (CCCD)
+  pCharacteristic->addDescriptor(new BLE2902());
+  // Adds also the Characteristic User Description - 0x2901 descriptor
+  descriptor_2901 = new BLE2901();
+  descriptor_2901->setDescription("GPS Data");
+  descriptor_2901->setAccessPermissions(ESP_GATT_PERM_READ);  // enforce read only - default is Read|Write
+  pCharacteristic->addDescriptor(descriptor_2901);
+
+  // Start the service
+  pService->start();
+
+  // Start advertising
+  BLEAdvertising *pAdvertising = BLEDevice::getAdvertising();
+  pAdvertising->addServiceUUID(SERVICE_UUID);
+  pAdvertising->setScanResponse(true);
+  pAdvertising->setMinPreferred(0x0);  // set value to 0x00 to not advertise this parameter
+  BLEDevice::startAdvertising();
+  Serial.println("Waiting a client connection to notify...");
+
+}
+
+
+void loop() {
+  while (Serial1.available()) {
+      gps.encode(Serial1.read());
+  }
+
+  if (deviceConnected && gps.location.isUpdated()) {
+    // parse GPS data
+    latUnion.lat = gps.location.lat();
+    longUnion.lng = gps.location.lng();
+    speedUnion.speed = gps.speed.mps();
+    yearUnion.year = gps.date.year();
+    monthUnion.month = gps.date.month();
+    dayUnion.day = gps.date.day();
+    hourUnion.hour = gps.time.hour();
+    minUnion.min = gps.time.minute();
+    secUnion.sec = gps.time.second();
+    centUnion.cent = gps.time.centisecond();
+
+    // create data packet for BLE transfer
+    uint8_t dataPacket[32];
+    dataPacket[0] = latUnion.bytes[0];
+    dataPacket[1] = latUnion.bytes[1];
+    dataPacket[2] = latUnion.bytes[2];
+    dataPacket[3] = latUnion.bytes[3];
+    dataPacket[4] = latUnion.bytes[4];
+    dataPacket[5] = latUnion.bytes[5];
+    dataPacket[6] = latUnion.bytes[6];
+    dataPacket[7] = latUnion.bytes[7];
+    dataPacket[8] = longUnion.bytes[0];
+    dataPacket[9] = longUnion.bytes[1];
+    dataPacket[10] = longUnion.bytes[2];
+    dataPacket[11] = longUnion.bytes[3];
+    dataPacket[12] = longUnion.bytes[4];
+    dataPacket[13] = longUnion.bytes[5];
+    dataPacket[14] = longUnion.bytes[6];
+    dataPacket[15] = longUnion.bytes[7];
+    dataPacket[16] = speedUnion.bytes[0];
+    dataPacket[17] = speedUnion.bytes[1];
+    dataPacket[18] = speedUnion.bytes[2];
+    dataPacket[19] = speedUnion.bytes[3];
+    dataPacket[20] = speedUnion.bytes[4];
+    dataPacket[21] = speedUnion.bytes[5];
+    dataPacket[22] = speedUnion.bytes[6];
+    dataPacket[23] = speedUnion.bytes[7];
+    dataPacket[24] = yearUnion.bytes[0];
+    dataPacket[25] = yearUnion.bytes[1];
+    dataPacket[26] = monthUnion.bytes[0];
+    dataPacket[27] = dayUnion.bytes[0];
+    dataPacket[28] = hourUnion.bytes[0];
+    dataPacket[29] = minUnion.bytes[0];
+    dataPacket[30] = secUnion.bytes[0];
+    dataPacket[31] = centUnion.bytes[0];
+
+    // notify changed value
+    if (deviceConnected) {
+      pCharacteristic->setValue((uint8_t *)&dataPacket, 32);
+      pCharacteristic->notify();
+      delay(10);
+    }
+  }
+
+  // disconnecting
+  if (!deviceConnected && oldDeviceConnected) {
+    delay(500);                   // give the bluetooth stack the chance to get things ready
+    pServer->startAdvertising();  // restart advertising
+    Serial.println("start advertising");
+    oldDeviceConnected = deviceConnected;
+  }
+
+  // connecting
+  if (deviceConnected && !oldDeviceConnected) {
+    oldDeviceConnected = deviceConnected;
+  }
+}