Ted's Cessna Knobox
===================

.. raw:: html

    <div align="center">
    <img src="https://raw.githubusercontent.com/Determinant/cessna-knobox/master/front.jpg" width="70%">
    <img src="https://raw.githubusercontent.com/Determinant/cessna-knobox/master/internal.jpg" width="70%">
    </div>


Materials
---------

- Part I (mechanical)

  - a friction-locked throttle knob (I used `A820 <https://www.aircraftspruce.com/catalog/appages/a820.php>`_)
  - a vernier-style mixer knob (I used `A790 <https://www.aircraftspruce.com/catalog/appages/a7902.php>`_)
  - hardboard, 3.5mm in thickness
  - M3 screws x4 for securing the potentiometers to the holders
  - M2 screws x4 for securing the knob ends to the potentiometer sliders
  - (M2.5/M3 screws + nuts) x4 for securing the holders to the enclosure
  - you'll need to laster-cut the hardboard and 3D-print the holders/sliders

- Part II (circuitry)

  - stmf103c8t6 board & ST-link programmer (something like https://www.ebay.com/itm/2pcs-STM32F103C8T6-ARM-STM32-Development-Board-Module-Blue-Pill-ST-Link-V2-USA/292168190439)
  - slide potentiometer (10K, 88mm in length, https://www.amazon.com/gp/product/B07QVQ67MV/ref=ppx_yo_dt_b_asin_title_o06_s00?ie=UTF8&psc=1)
  - 3 SPDT switches + 1 SPDT toggle switch
  - 5 resistors (15K)
  - micro-USB to USB type-A cable (https://www.ebay.com/itm/90-Degree-Left-Angled-Micro-USB-5pin-Male-to-USB-B-Female-Panel-Mount-Type-Cable/162358249642)
  - (optional) mounting jig (https://www.amazon.com/gp/product/B07BHXXR4D/ref=ppx_yo_dt_b_asin_title_o01_s00?ie=UTF8&psc=1 works very well, but you'll need to drill the holes yourself)

3D Printed Components
---------------------

- Holders: ``holder.stl``
- Sliders: ``slider1.stl``, ``slider2.stl``

Enclosure
---------

- Part 1: ``cessna-knobox-enclosure1.svg``
- Part 2: ``cesnna-knobox-enclosure2.svg``

Circuitry
---------

- Configure the potentiometers as voltage diviers:

  - Connect two ends to have 3.3v difference in voltage
  - Connect the pivot pins to A1 and A2 of the microcontroller

- Configure the switches as pull-up inputs:

  - Connect the middle pin of all switches to the ground (G/GND)
  - Parallel one side of the resistors (15K x5) to be 5V (5V pin)
  - Connect the other side of each resistor as shown in the diagram:

    - One (left/right) pin from each of three switches connects to A8, A9, A10, respectively
    - Pins (left & right) of the fourth switch connect to B14, B15.
    - Note: the lower right switch is a SPDT switch that springs to off when no
      pressure is applied. It could be used as flap control.

.. raw:: html

    <div align="center">
    <img src="https://raw.githubusercontent.com/Determinant/cessna-knobox/master/cessna-knobox-circuit.svg" width="40%">
    </div>


Firmware
--------

- (optional) To build the firmware from source, run ``./build_image.sh`` (make sure you
  have Rust/Cargo installed on your computer)
- Or you can use a pre-built image already available at ``./cessna-knobox.bin``
- Flash the image to the microcontroller using ST-link (you can either use the tool provided officially by ST, or do it in openocd)