I’ve just removed and replaced the last OpenCockpits Hardware, the Forward Overhead Panel, which was connected via USB to the flight simulator. Apart from the extensive wiring needed, USB devices by OpenCockpits were quite difficult to use because a) their communication protocol is not “Open” as the name misleadingly suggests, and b) the OpenCockpits USB devices have no serial number, thus cannot be distinguished from each other. This last point made is rather difficult to run them reliably, since accessing two servo cards (e.g. one driving the fuel temperature servo and the other driving the cabin pressure servo) was always a lottery. We don’t want to fly by luck, anyway.
Here are some pictures of the “old” Forward Overhead Panel. Nicely built, but too much wiring and occupying 3 USB ports. The last image shows all the hardware panels which were needed.
The new world is called “Ethernet” and Teensy and consists of a universal Teensy firmware which listens to the flight simulator and allows to be on-the-fly programmed for any attached inputs / outputs or daughter boards via the I2C bus. The new Forward Overhead Panel has the following hardware structure:
- Teensy 4.1 Controller with Ethernet and I2C interface
- 19 MCP23017 16 Input / Output boards via I2C
- 2 PCA9685 PWM / Servo Output boards via I2C
- 2 HT16K33 7 Segment LED boards via I2C
The new Panel also features 4 Solenoid Switches:
- Yaw Damper Switch
- Engine 1 Start Switch
- Engine 2 Start Switch
- Wing Ice Switch
The New Panel also features 16 latched Switches like in the real aircraft and it is mounted on a original B737-300 overhead frame, plus includes three original LED-retrofitted panels and a few original and LED-retrofitted Korry annunciators. Beautiful stuff, see here:
As you can see from the last image, the amount of wiring has not gone to 0. However, each panel can be detached without removing the overhead since each panel only has a 4 wire I2C connector, one Interrupt wire and a 12V backlighting connector. This could be optimized by a generalized panel interface (using e.g. a 6 wire plug).
Flight test is underway, but the new Forward Overhead Panel looks stable so far …
Teensy Code as part of the xpcockpits framework available on Github here.