A function to parse Eddystone TLM frames.

ParseTelemetry.swift

  static let kEddystoneTLMFrameByteCount = 14;
  static let EddystoneTLMFrameTypeID: UInt8 =  0x20

  private func parseTelemetryFrame(telemetryFrame : NSData) {
    let count = telemetryFrame.length
    if count == ThisClassName.kEddystoneTLMFrameByteCount {
      var frameType: UInt8 = 0
      telemetryFrame.getBytes(&frameType, length: sizeof(UInt8))
      if frameType != ThisClassName.EddystoneTLMFrameTypeID {
        NSLog("This is not a TLM frame")
        return
      }

      var tlmVersion: Int8 = 0
      telemetryFrame.getBytes(&tlmVersion, range: NSMakeRange(1, sizeof(UInt8)))
      if tlmVersion != 0 {
        NSLog("Unknown TLM frame version")
        return
      }

      var batteryVoltage: UInt16 = 0
      telemetryFrame.getBytes(&batteryVoltage, range: NSMakeRange(2, sizeof(UInt16)))
      batteryVoltage = UInt16(bigEndian: batteryVoltage)

      // This is in 8.8 fixed point. Just have to divide by 256 to get the actual number.
      var beaconTemperatureFixed: Int8 = 0
      var beaconTemperatureFractional: UInt8 = 0
      telemetryFrame.getBytes(&beaconTemperatureFixed, range: NSMakeRange(4, sizeof(Int8)))
      telemetryFrame.getBytes(&beaconTemperatureFractional, range: NSMakeRange(5, sizeof(UInt8)))

      let beaconTemperature = Float(beaconTemperatureFixed)
        + Float(beaconTemperatureFractional) / 256.0

      var advertisingPDUCount: UInt32 = 0
      telemetryFrame.getBytes(&advertisingPDUCount, range: NSMakeRange(6, sizeof(UInt32)))
      advertisingPDUCount = UInt32(bigEndian: advertisingPDUCount)

      var timeOnSincePowerOn: UInt32 = 0
      telemetryFrame.getBytes(&timeOnSincePowerOn, range: NSMakeRange(10, sizeof(UInt32)))
      timeOnSincePowerOn = UInt32(bigEndian: timeOnSincePowerOn)

      NSLog("TLM Frame: voltage: %d temp: %f PDU count: %u time on: %u",
            batteryVoltage, beaconTemperature, advertisingPDUCount, timeOnSincePowerOn)
    }
  }