MeshCore/src/helpers/nrf52/SerialBLEInterface.cpp

#include "SerialBLEInterface.h"

void SerialBLEInterface::begin(const char* device_name, uint32_t pin_code) {
  char charpin[20];
  sprintf(charpin, "%d", pin_code);

  Bluefruit.configPrphBandwidth(BANDWIDTH_MAX);
  Bluefruit.configPrphConn(250, BLE_GAP_EVENT_LENGTH_MIN, 16, 16);  // increase MTU
  Bluefruit.begin();
  Bluefruit.setTxPower(4);    // Check bluefruit.h for supported values
  Bluefruit.setName(device_name);

  Bluefruit.Security.setMITM(true);
  Bluefruit.Security.setPIN(charpin);

  // To be consistent OTA DFU should be added first if it exists
  //bledfu.begin();
}

void SerialBLEInterface::startAdv() {
  // Advertising packet
  Bluefruit.Advertising.addFlags(BLE_GAP_ADV_FLAGS_LE_ONLY_GENERAL_DISC_MODE);
  Bluefruit.Advertising.addTxPower();
  
  // Include the BLE UART (AKA 'NUS') 128-bit UUID
  Bluefruit.Advertising.addService(bleuart);

  // Secondary Scan Response packet (optional)
  // Since there is no room for 'Name' in Advertising packet
  Bluefruit.ScanResponse.addName();

  /* Start Advertising
   * - Enable auto advertising if disconnected
   * - Interval:  fast mode = 20 ms, slow mode = 152.5 ms
   * - Timeout for fast mode is 30 seconds
   * - Start(timeout) with timeout = 0 will advertise forever (until connected)
   * 
   * For recommended advertising interval
   * https://developer.apple.com/library/content/qa/qa1931/_index.html   
   */
  Bluefruit.Advertising.restartOnDisconnect(true);
  Bluefruit.Advertising.setInterval(32, 244);    // in unit of 0.625 ms
  Bluefruit.Advertising.setFastTimeout(30);      // number of seconds in fast mode
  Bluefruit.Advertising.start(0);                // 0 = Don't stop advertising after n seconds 
}

// ---------- public methods

void SerialBLEInterface::enable() { 
  if (_isEnabled) return;

  _isEnabled = true;
  clearBuffers();

  // Configure and start the BLE Uart service
  bleuart.setPermission(SECMODE_ENC_WITH_MITM, SECMODE_ENC_WITH_MITM);
  bleuart.begin();

  // Start advertising
  startAdv();

  checkAdvRestart = false;
}

void SerialBLEInterface::disable() {
  _isEnabled = false;

  BLE_DEBUG_PRINTLN("SerialBLEInterface::disable");

  Bluefruit.Advertising.stop();

  oldDeviceConnected = deviceConnected = false;
  checkAdvRestart = false;
}

size_t SerialBLEInterface::writeFrame(const uint8_t src[], size_t len) {
  if (len > MAX_FRAME_SIZE) {
    BLE_DEBUG_PRINTLN("writeFrame(), frame too big, len=%d", len);
    return 0;
  }

  if (deviceConnected && len > 0) {
    if (send_queue_len >= FRAME_QUEUE_SIZE) {
      BLE_DEBUG_PRINTLN("writeFrame(), send_queue is full!");
      return 0;
    }

    send_queue[send_queue_len].len = len;  // add to send queue
    memcpy(send_queue[send_queue_len].buf, src, len);
    send_queue_len++;

    return len;
  }
  return 0;
}

#define  BLE_WRITE_MIN_INTERVAL   60

bool SerialBLEInterface::isWriteBusy() const {
  return millis() < _last_write + BLE_WRITE_MIN_INTERVAL;   // still too soon to start another write?
}

size_t SerialBLEInterface::checkRecvFrame(uint8_t dest[]) {
  if (send_queue_len > 0   // first, check send queue
    && millis() >= _last_write + BLE_WRITE_MIN_INTERVAL    // space the writes apart
  ) {
    _last_write = millis();
    bleuart.write(send_queue[0].buf, send_queue[0].len);
    BLE_DEBUG_PRINTLN("writeBytes: sz=%d, hdr=%d", (uint32_t)send_queue[0].len, (uint32_t) send_queue[0].buf[0]);

    send_queue_len--;
    for (int i = 0; i < send_queue_len; i++) {   // delete top item from queue
      send_queue[i] = send_queue[i + 1];
    }
  } else {
    int len = bleuart.available();
    if (len > 0) {
      deviceConnected = true; // should probably use the callback to monitor cx 
      bleuart.readBytes(dest, len);
      BLE_DEBUG_PRINTLN("readBytes: sz=%d, hdr=%d", len, (uint32_t) dest[0]);
      return len;
    }
  }

  if (Bluefruit.connected() == 0)  deviceConnected = false;

  if (deviceConnected != oldDeviceConnected) {
    if (!deviceConnected) {    // disconnecting
      clearBuffers();

      BLE_DEBUG_PRINTLN("SerialBLEInterface -> disconnecting...");
      delay(500); // give the bluetooth stack the chance to get things ready

      checkAdvRestart = true;
    } else {
      BLE_DEBUG_PRINTLN("SerialBLEInterface -> stopping advertising");
      BLE_DEBUG_PRINTLN("SerialBLEInterface -> connecting...");
      // connecting
      // do stuff here on connecting
      Bluefruit.Advertising.stop();
      checkAdvRestart = false;
    }
    oldDeviceConnected = deviceConnected;
  }

  if (checkAdvRestart) {
    if (Bluefruit.connected() == 0) {
      BLE_DEBUG_PRINTLN("SerialBLEInterface -> re-starting advertising");
      startAdv();
    }
    checkAdvRestart = false;
  }
  return 0;
}

bool SerialBLEInterface::isConnected() const {
  return deviceConnected;  //pServer != NULL && pServer->getConnectedCount() > 0;
}