MAVLinkView

An Arduino sketch for showing MAVLink telemetry data

Use case

I'm using this to show telemetry data on my Open.HD ground station. In this case, the data is provided by a Raspberry Pi via the serial interface on the GPIO port.

Features

• It shows telemetry data on a small display. Additional to the directly received parameters, the home distance of the vehicle is calculated and shown.
• There is a timeout monitoring of the belonging MAVLink messages, a timeout is indicated by a blinking value label.
• In case of message timeout, the last received data will be stored permanently into EEPROM - it will be shown until new data arrives, even after a power cycle. This can be very useful if you lost your vehicle.
• There is one touch sensor field provided for toggling between the default text mode and a QR mode.
• The code shown in QR mode is intented to be scanned by a smartphone for fast navigation to the last known vehicle position. Various map providers are selectable at compile time.

Hardware

At the moment I'm running the sketch on a Teensy® LC, but any other 32bit Teensy® or Arduino should work as well. Please note, that the Teensy® LC is pretty much maxed out in terms of Flash Memory - if you want to add some more features it may be wise to choose a device with more than 64kB Flash.

The display is required to have a resolution of 128 x 64 pixels, I'm using a SPI controlled OLED type from here. During my tests I found that the multiplexed control scheme of the OLED display may interfere with some smartphone cameras (rolling shutter) while trying to scan the QR code. I suppose, an E-Ink display would perform better in that area. Anyways, before choosing a display please make sure that it is supported by the u8g2 library!

The touch sensor can be a small piece (> 20mm x 20mm) of self-adhesive copper film or sheet metal, soldered on a short wire and connected to a touch enabled Arduino pin.

Customization

• If you don't use a display with SSD1306 (or compatible) or if it is not controlled by hardware SPI (4 wire), the u8g2 constructor needs to be adapted accordingly.
• Check if all Arduino pin numbers match your hardware.
• Adapt the touch sensor threshold by executing the following steps:
  1. Uncomment this line of code:
     //#define DebugTouch
  2. Build and watch the debug output. Note the value for touchLevel once the sensor is untouched and once it is touched.
  3. Subtract some safety margin from the touched value and enter it in this line of code:
     const int TouchOnLevel = 680;
  4. Add some safety margin to the untouched value and enter it in this line of code:
     const int TouchOffLevel = 620;
  5. Build again and watch the debug output. The shown value for sensorTouched should be 0 in case the sensor is untouched and 1 if the sensor is touched.
  6. If you are happy with the result, comment the line again you uncommented in the first step.
• Optional, you could change the map provider used in QR code generation in this line of code:
  const MapProvider_t MapProvider = MapProviderGoogle; // select map provider

Build the code

Place the contents of the Arduino folder into your Arduino sketch folder and install the following libraries via the Arduino Library Manager:

• u8g2: https://github.com/olikraus/u8g2
• CRC: https://github.com/RobTillaart/CRC

Credits

This sketch wouldn't be possible in it's current form without including code from different sources directly:

• MAVLink: https://mavlink.io
• QR Code generator library: https://github.com/nayuki/QR-Code-generator
• Haversine formula should be public domain.