This utility converts a ".hex" binary file into a ".h" file which contains a byte array to be included in "timonel-twim-ss" or "timonel-twim-ms".
The AVR binary files should be placed into the "appl-flashable" folder. They can be generated using any editor + the avr-gcc toolchain, Atmel Studio 7 or the Arduino IDE. If you use Arduino IDE, the compiled .hex files are a bit hard to find, use these instructions to find them: "https://arduino.stackexchange.com/questions/48431/how-to-get-the-firmware-hex-file-from-a-ino-file-containing-the-code".
Once that you have the desired .hex in the "appl-flashable" folder, just run
$ ./make-payload.sh appl-flashable/attiny_firmware.hex to convert it into a payload.
The script leaves a ".h" file with the same name of the ATtiny firmware file into the "appl-payload" and "timonel-twim-ss/data/payloads" folders.
The "timonel-twim-ss" application must be recompiled and flashed to the master device before being able to flash the payload to the AVR device running Timonel.