Glareshield Expansion - Annunciator Panel
The center glareshield sections are substituted by the glareshield expansion. It holds place for one potentiometer (instrument illumination brightness) and five elements 30 mm x 30 mm. In the current stage one element contains three LED for the runway markers: O-M-I blue, red and white respectively.
One element contains a temperature gauge for OAT (outside air temperature) and TAT (true air temperature). The element adjacent to the temperature gauge has a switch to toggle the temperature display between °C and °F.
The display is a 0.96" 128x62 I2C OLED display.
Since Mobiflight to date is not capable of addressing the OLED display directly, the OLED is controlled with an Arduino Nano.
Here is how it works:
- In Mobiflight an input mapping is created as a button named TATRequest. It drives a variable TATRequest when input is 1.
- In Mobiflight an output mapping is created which only contains the Mobiflight variable TATRequest.
- In Mobiflight an output mapping is created for each OAT and TAT as a servo.
- If TATRequest is 0, Mobiflight sends the OAT value (-50°C to 50°C) as a value from 0 to 100 to the servo output.
- If TATRequest is 1, Mobiflight sends the TAT value (-50°C to 50°C) as a value from 0 to 100 to the servo output.
- The Arduino NANO polls the temperature values as follows:
- The output connected to the TATRequest pin of Mobiflight is set to zero. Mobiflight in this case sends the OAT as a servo value. Pin 2 of the NANO is configured as an interrupt pin and gives the servo value (approx 544 - 2400). The actual value depends on the MEGA and your mileage may vary. The NANO then maps the servo value to the actual temperature value and according to the switch (Input to the NANO) displays the temperature either as °C or °F.
- After 1000 milliseconds, the TATRequest pin is set to HIGH (1) and then Mobiflight sends the OAT value which will be calculated and displayed accordingly.
The polling time is set considerably long with two seconds overall. Since the temperature values are not fluctuating very fast, this is no problem at all. Very often, Mobiflight servo values may have some slight jitter. During test flights this setup proved to be sufficient reliable and accurate. The values shown in the simulator may differ slightly from the displayed values.
The two elements to the left are meant to house some illuminated warning panels such as low vac, low voltage, low oil pressure etc.