i2c-tiny-usbasp

Fork of the i2c-tiny-usb project for use on USBasp hardware.

Notes

Tested on a cheap (atmega8 based) USBasp V2 board which is available on many selling portals.

This repository contains only the modified firmware with usbtiny stack. firmware/firmware.hex is a precompiled version you can use to flash your USBasp board.

Modifications done:

• removed all usb stacks excepting usbtiny
• updated usbtiny stack (v1.7) with fast CRC enabled
• two LEDs configured for "USB OK" and "USB TX" notifications
• updated LED on/off control in usbtiny
• removed attiny45 code
• updated USB D+ D- pins to fit USBasp hardware (D+ is PB1, D- is PB0)
• updated I2C pins to fit USBasp hardware (SCL is PB5, SDA is PB4)
• removed all makefiles excepting one for USBasp with atmega8
• updated Makefile to use python3 for check.py
• updated usbtiny makefile to build firmware.hex instead of main.hex
• make flash will flash without building

Compiling the firmware

• Install AVR GCC toolchain. Under Ubuntu/Debian you can use following command: sudo apt install avr-libc binutils-avr gcc-avr avrdude make
• clone this repository and change working directory in terminal to firmware subfolder
• run make to build

Uploading the firmware

Easiest way to program the USBasp board with the i2c-tiny-usb firmware is to use another USBasp board.

• Bridge the JP2 Self program pins of the target USBasp device
• Connect another USBasp device (as programmer) to the target board
• Put the programmer USBasp into USB port of your PC
• run make flash from firmware subfolder to flash firmware.hex to the target USBasp
• remove JP2 Self program bridge

Pinout

Testing (Linux)

• Connect the flashed USBasp device to your linux machine
• install i2c-tools package (e.g. sudo apt install i2c-tools)
• run i2cdetect -l, i2-tiny-usb interface should be listed