private async Task _disconnect()
{
try
{
_characteristicHR.ValueUpdated -= CharacteristicHR_ValueUpdated;
await _characteristicHR.StopUpdatesAsync();
await _adapter.DisconnectDeviceAsync(_device);
_connectionRetry = 0;
_device = null;
_serviceHR = null;
_serviceBattery = null;
_characteristicHR = null;
_characteristicBatteryLevel = null;
_currentValue = null;
_log("_disconnect", "disconnected");
}
catch (Exception e)
{
_log("_disconnect", e.Message);
}
}
private async void CharacteristicHR_ValueUpdated(object sender, Plugin.BLE.Abstractions.EventArgs.CharacteristicUpdatedEventArgs args)
{
// https://www.bluetooth.com/specifications/gatt/viewer?attributeXmlFile=org.bluetooth.characteristic.heart_rate_measurement.xml
// https://www.bluetooth.com/specifications/gatt/viewer?attributeXmlFile=org.bluetooth.characteristic.battery_level.xml
try
{
int heartValue;
var bytes = args.Characteristic.Value;
byte flags = bytes[0];
int header;
if ((flags & 0x1) == 0x1)
{
// HB data is 16 bits (bytes[2]bytes[1] since it's LSB first)
header = (bytes[2] >> 4); // First 4 bits
heartValue = bytes[1] | ((0xF & bytes[2]) << 8); // Next 12
if (heartValue == 0xFFF)
{
heartValue = -1;
}
if (_update_func != null)
{
await _update_func(header, heartValue);
}
}
else
{
header = 0;
heartValue = bytes[1];
if (_update_func != null)
{
await _update_func(header, heartValue);
}
}
if (_currentValue == null)
{
_currentValue = new HeartRateData();
}
_currentValue.Value = bytes[1];
_currentValue.Timestamp = DateTime.Now;
if (_characteristicBatteryLevel != null)
{
if (_currentValue.TimestampBatteryLevel == null ||
(DateTime.Now - _currentValue.TimestampBatteryLevel).Value.Minutes > 1)
{
_currentValue.BatteryLevel = null;
var batteryLevelByte = await _characteristicBatteryLevel?.ReadAsync();
_currentValue.TimestampBatteryLevel = DateTime.Now;
_currentValue.BatteryLevel = batteryLevelByte[0];
}
}
_log("CharacteristicHR_ValueUpdated", $"Device {_currentValue.Value}");
}
catch (Exception e)
{
_log("CharacteristicHR_ValueUpdated", e.Message);
}
}