Ardunio sketch for a 3 button push to talk pedal
This is using an Arduino Uno Rev. 3 as an HID device to send serial signals via USB.
The UNO doesn't support HID functionality out of the box, so flashing the firmware is required. You can flash using Amtel FLIP as described http://www.kevindemarco.com/2014/01/02/arduino-uno-as-a-usb-hid-interface/ Windows installation instructions can be found here
My workflow:
- Program Arduino ATMega16u2 chip with Flip by plugging in USB -> short pins with paper clip -> Program with the following Hex file https://github.com/arduino/Arduino/blob/master/hardware/arduino/avr/firmwares/atmegaxxu2/arduino-usbserial/Arduino-usbserial-atmega16u2-Uno-Rev3.hex
- Power cycle Arduino by unplugging then re-plugging the USB
- Upload ptt_buttons.ino sketch file to Arduino
- Short pins and now re-program ATMega16u2 using the above process with Arduino-keyboard-0.3.hex file
- Power cycle Arduino and you should now have a USB HID button device
To change the buttons that are triggered, simply change the serial codes at:
The following binds are 'Left Ctrl', '[' and ']' respectively. Note that the KEY_LEFT_CTRL is passed as a 'Modifier' at array position 0.
#define KEY_BUTTON_A 0x2F
#define KEY_BUTTON_B 0x30
Key modifiers are defined in the IEEE HID Spec as follows:
LEFT CONTROL 1 # 00000001 as binary
LEFT SHIFT 2 # 00000010
LEFT ALT 4 # 00000100
LEFT CMD|WIN 8 # 00001000
RIGHT CONTROL 16 # 00010000
RIGHT SHIFT 32 # 00100000
RIGHT ALT 64 # 01000000
RIGHT CMD|WIN 128 # 10000000
Modifiers can be combined:
LEFT CTRL + LEFT SHFIT = 1 + 2 = 3
LEFT CTRL + LEFT ALT + LEFT SHIFT = 1 + 2 + 4 = 7
For serial code references please see http://www.usb.org/developers/hidpage/Hut1_12v2.pdf
