Ready to deploy design #6

Read this document from start to end before building anything. Ensure you understand everything.

This setup has been tested.

Hardware features

• Bluetooth Low Energy
• Powered through external power source
• Analog clutch paddles (potentiometers) x2
• Shift paddles (x2)
• "ALT" buttons (x2)
• Relative rotary encoders (with push button): x4
• Up to 14 additional push buttons

Button mapping

• Bite point calibration: rotary #1 clockwise and counter-clockwise (while holding one and only one clutch paddle).
• Next clutch function: Rotary #1 push button and Left shift paddle.
• ALT buttons mode: Rotary #1 push button and Right shift paddle.
• Recalibrate clutch paddles: Left shift paddle, Right shift paddle and Rotary #1 push button.

Do not hold Rotary #2 push button at startup, or it won't boot (but may be used to force "bootloader mode").

Needed parts

Item	Quantity	Notes
Lolin32 Lite DevKit board	1	NO PIN HEADERS already soldered
Row of 13 male pin headers	2 rows	Maybe they are included in your Lolin32 Lite purchase
Standard perfboard sized 24x10 holes	1	Double side recommended
Kit of Dupond wires the kind used in protoboards	1 kit	See below
Analog multiplexer	2	74HC4051N (mandatory)
Roller lever switch	2	For shift paddles (maybe they are included with your wheel's case)
Linear potentiometer (any impedance)	2	For clutch paddles (maybe they are included with your wheel's case)
Bare bone Rotary encoder	4
Push buttons	up to 16	General purpose inputs (up to you)
Female pin header	26	In order to attach the DevKit board to the main board
Other male pin headers	32	For external wiring
Power connector depending on your quick release	1	See below
Male micro-USB plug	1	For power

Other parts (quantity unknown):

• Thin wire. You may sacrifice some unused Dupond wires in replacement.
• Welding tin.

Additional notes:

• Chose an appropriate male/female power connector depending on your quick release. Make sure to identify the positive and negative terminals correctly. If you have a Simagic QR, negative is the yellow wire and positive is the green one.
• For the male micro-USB plug you may reuse an spare USB cable. Cut one end.
• Make sure you have enough Dupond wires in your kit. You may use them both for internal and external wiring. Check they have the proper length for your needs.

Pin-out plan for the Lolin32 Lite board

GPIO	Input	Output	Usage	Notes
36	OK		Left pot	input only (no internal pull resistor)
39	OK		Right pot	input only (no internal pull resistor)
34	OK			input only (no internal pull resistor)
35	OK			input only (no internal pull resistor)
32	OK	OK	ROT1_A
33	OK	OK	ROT1_B
25	OK	OK	ROT2_A
26	OK	OK	ROT2_B
27	OK	OK	ROT3_A
14	OK	OK	Multiplexer input 1	outputs PWM signal at boot
12	OK	OK	ROT3_B	boot fail if pulled high
13	OK	OK	ROT4_A
15	OK	OK	ROT4_B	outputs PWM signal at boot
2	OK	OK	ROT1_SW	connected to on-board LED
0	pulled up?	OK	ROT2_SW	outputs PWM signal at boot
4	OK	OK	ROT3_SW
16	OK	OK	Multiplexer selector 1
17	OK	OK	Multiplexer selector 2
5	OK	OK	Multiplexer selector 3	outputs PWM signal at boot
18	OK	OK	ROT4_SW
23	OK	OK	Shift Paddle switch
19	OK	OK	Shift Paddle switch
22	OK	OK	Multiplexer input 2

Power cable

You have to build this by yourself. One end requires a male micro-USB plug. The other end requires a proper connector matching that of your quick release. You can find the USB pin-out in the Internet. Note that just the 5V (positive terminal) and GND (negative terminal) pins need to be wired, but the USB plug features 5 pins. If you have an already wired plug, the red wire is 5V and the black one is GND.

USB Tag	USB male plug	USB wire color	Your QR plug	Simagic QR plug (if applies)
5V	pin #1	red	positive terminal	green wire
GND	pin #5	black	negative terminal	yellow wire

Pin headers for the DevKit board

You also have to build this by yourself. The DevKit board will be mounted upside-down into the main board. So you have to solder the male pin headers facing up, as shown in the following picture:

Circuit layout

Open the circuit layout using DIY Layout Creator. If you need a clear view of the back traces, hide the wires in DIY by hitting CTRL+5.

This layout includes the following subsystems (read for an in-depth explanation):

• Analog clutch paddles.
• Power via USB connector.
• Switches through analog multiplexers.
• Relative rotary encoder.

Notes and build tips:

• There is a lot of wiring, which is prone to human error. Check wiring and traces twice before soldering.
• We are using some Dupond wires instead of pin headers, so you have to cut the connector at one end. This simplifies the circuit a lot. Put a label on those wires using a piece of paper and adhesive tape in order to know which is which.
• Note that the striped wires are soldered on the back side while the others are soldered on the front side.
• The packaging of the analog multiplexers will show a small circle next to pin #1, which is tagged as A4 here.
• Make sure to place the analog multiplexers properly. Note that both multiplexers are placed symmetrically, not pointing to the same place.
• When finished, put some isolation tape at the back of the main circuit board.

External wiring

• There are many redundant GND pin headers. Use them as you wish, but it is easier to wire all the required terminals together in a chain to a single GND pin.
• Each input has an assigned number in the circuit layout. Certain inputs have a particular function, so attach them properly.
• The POTn_GND and POTn_VCC terminals of each potentiometer are interchangeable. If the clutch (or axis) goes to 100% when idle, swap those terminals. If you don't have the chance to swap those terminals, the companion app has the ability to swap axis polarity by user request.
• Note that the pin headers on the left and right clutch paddles are symmetrical, not identical.
• Bare bone rotary encoders:
  • The involved terminals are:
    • For rotation: A or CLK attached to ROTn_A, B or DT attached to ROTn_B, COM attached to GND.
    • The built-in push button must be wired as any other push button, being SW and SW COM the involved terminals. SW attached to their reserved pin headers and SW COM attached to GND.
  • You may wire COM and SW COM together, since both must be attached to GND.
  • Rotary encoder #1 is mandatory.

Firmware upload

At Arduino IDE, configure the board manager for "WEMOS LOLIN32 Lite".

1. Detach the DevKit board from the circuit before continuing.
2. Plug the USB cable to the Devkit board and upload the sketch with Arduino IDE.
3. Attach the DevKit board to the circuit. Keep the USB cable plugged in.
4. Open the serial monitor (Arduino IDE).
5. Reset.
6. Check there are no error messages.