AutoPTT Sidekick

AutoPTT Sidekick is a virtual USB keyboard that can be controlled from the computer it's plugged into.

I made this for AutoPTT because some games like CSGO require a physical key press to activate push-to-talk, and, as far as Windows knows, this thing is a physical keyboard. :)

I initially implemented this for an old AT90USB162 board (Minimus V1) as a proof of concept. Since that board isn't really available anywhere anymore, I also implemented it for basically any ATmega32u4-based board. I've tried it on a Sparkfun Pro Micro and an Adafruit ItsyBitsy, both of which are easily available and affordable.

Note that once this is flashed on an Arduino, further attempts at flashing will require you to manually enter the bootloader by pressing the reset button twice as the Arduino desktop application will no longer be able to do it automatically.

The Sparkfun Pro Micro doesn't have a reset button though, so instead, you'll have to connect the RST and GND pins (which is what the button would have done).

Source: https://learn.sparkfun.com/tutorials/pro-micro--fio-v3-hookup-guide#ts-reset

Releases

You can download prebuilt binaries from Github. They are built with USB Vendor ID 0x1209 and Product ID 0xE1E1, generously provided by pid.codes.

The ItsyBitsy build should work for pretty much any ATmega32u4 board.

Build it yourself

You can also build the binary yourself in case you want to make changes.

Requirements

• Linux
• git
• docker
• earthly

Copy cfg.example.mk to cfg.mk, then edit the values accordingly. Once you're done with that, run

earthly +build

If everything goes as planned, you'll find itsy-bitsy.hex and minimus.hex in the build/earthly directory.

Flash it

On an Arduino

Reminder: To manually enter the bootloader, press the reset button twice!

For example, this is how you would do it on an Adafruit ItsyBitsy:

Install arduino-cli, then do the initial setup

arduino-cli config init
arduino-cli config add board_manager.additional_urls https://adafruit.github.io/arduino-board-index/package_adafruit_index.json
arduino-cli core update-index
arduino-cli core install arduino:avr
arduino-cli core install adafruit:avr

This is how you would flash it on Linux, provided that the USB device is at /dev/ttyACM0 and itsy-bitsy.hex is in the current directory.

arduino-cli upload -v -b adafruit:avr:itsybitsy32u4_5V -p /dev/ttyACM0 -i itsy-bitsy.hex

On Windows, the command is very similar, but the device will be COM1 or something like that. You can find that out by opening Device Manger and looking under Ports (COM & LPT) while the device is in bootloader. It will most likely be COM1.

arduino-cli upload -v -b adafruit:avr:itsybitsy32u4_5V -p COM1 -i itsy-bitsy.hex

This short video demonstrates flashing on Windows.

On a Minimus

In case you happen to have a Minimus board, you can use dfu-programmer.

Install dfu-programmer with

sudo apt-get install -y dfu-programmer

Then use it to first erase and then flash the device

sudo dfu-programmer at90usb162 erase
sudo dfu-programmer at90usb162 flash build/earthly/minimus.hex

Try some commands

Once the device is flashed and plugged in, here are some commands you can use to test it on Linux. Note that you might have to change /dev/ttyACM0 to something else.

Change LED state

NOTE: Only works on Minimus at the moment.

payload
  u8 action = 0
  u8 led_id
  u8 led_on

Examples

blue led off

echo -ne '\x00\x01\x00' | sudo tee /dev/ttyACM0 >/dev/null

blue led on

echo -ne '\x00\x01\x01' | sudo tee /dev/ttyACM0 >/dev/null

red led off

echo -ne '\x00\x02\x00' | sudo tee /dev/ttyACM0 >/dev/null

red led on

echo -ne '\x00\x02\x01' | sudo tee /dev/ttyACM0 >/dev/null

Change keyboard state for single key

NOTE: Don't send modifier keys as key codes, they will be ignored.

payload
  u8 action = 1
  u8 key_code
  u8 is_down

See LUFA/Drivers/USB/Class/Common/HIDClassCommon.h for the key codes (HID_KEYBOARD_SC_*)

Examples

keyboard f down, wait 100ms, keyboard f up

echo -ne '\x01\x09\x01' | sudo tee /dev/ttyACM0 >/dev/null
sleep 0.1
echo -ne '\x01\x09\x00' | sudo tee /dev/ttyACM0 >/dev/null

Replace entire keyboard state

See LUFA/Drivers/USB/Class/Common/HIDClassCommon.h for the modifiers (HID_KEYBOARD_MODIFIER_*)

Modifiers are a bit mask, like HID_KEYBOARD_MODIFIER_LEFTCTRL | HID_KEYBOARD_MODIFIER_LEFTSHIFT = (1 << 0) | (1 << 1) = 3

payload
  u8 action = 2
  u8 modifiers
  u8 key_codes[6]

Key code value 0 means the key at that index is not used.

Key code with a valid key code means that key is currently down.

Duplicate key codes are ignored.

Examples

left shift, f
all up

echo -ne '\x02\x02\x09\x00\x00\x00\x00\x00' | sudo tee /dev/ttyACM0 >/dev/null
sleep 0.1
echo -ne '\x02\x00\x00\x00\x00\x00\x00\x00' | sudo tee /dev/ttyACM0 >/dev/null

Replace modifier state

payload
  u8 action = 3
  u8 modifiers

Examples

left ctrl, left shift
all up

echo -ne '\x03\x03' | sudo tee /dev/ttyACM0 >/dev/null
sleep 0.1
echo -ne '\x03\x00' | sudo tee /dev/ttyACM0 >/dev/null

Test

To build everything and run the tests, just do

earthly +all