This is a port of Till Harbaums' i2c_tiny_usb firmware to the Olimex FOSDEM-85 board that was handed out at FOSDEM'14.
The corresponding host side Linux driver has been in mainline for many years (CONFIG_I2C_TINY_USB), so with this you have easy access to the normal kernel I2C infrastructure through your FOSDEM-85 board.
The FOSDEM-85 board uses the nice
micronucleus
bootloader, so to upload this firmware simply connect the board to
your PC and run: micronucleus firmware.hex
> Please plug in the device ...
> Press CTRL+C to terminate the program.
> Device is found!
connecting: 40% complete
> Device has firmware version 2.3
> Device signature: 0x1e930b
> Available space for user applications: 6522 bytes
> Suggested sleep time between sending pages: 7ms
> Whole page count: 102 page size: 64
> Erase function sleep duration: 714ms
parsing: 60% complete
> Erasing the memory ...
erasing: 80% complete
> Starting to upload ...
writing: 100% complete
>> Micronucleus done. Thank you!
Connect I2C device(s) to FOSDEM-85 board (SDA is pin 0, SCL is pin 2,
VCC/GND) and connect USB cable to PC:
# i2cdetect -l | grep tiny
i2c-9 i2c i2c-tiny-usb at bus 003 device 003 I2C adapter
# i2cdetect -y 9
0 1 2 3 4 5 6 7 8 9 a b c d e f
00: -- -- -- -- -- -- -- -- -- -- -- -- --
10: -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- --
20: -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- --
30: -- -- -- -- -- -- -- -- 38 -- -- -- -- -- -- --
40: -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- --
50: 50 -- -- -- -- -- -- -- -- -- -- -- -- -- -- --
60: -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- --
70: -- -- -- -- -- -- -- --
# i2cset -f -y 9 0x38 0xfe
# i2cset -f -y 9 0x38 0xff
(This is with a setup with a 24c64 eeprom and pcf8574a gpio extender).
Notice that the green led will flash for each I2C transaction as debugging feedback.
Thanks to Till Harbaum for the original firmware and Olimex for the nice FOSDEM-85 board.