i2c-tiny-usb - (c) 2006 by Till Harbaum, updated by S. Baerwolf 2022
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http://matrixstorm.com/avr/tinyusbboard/
http://www.harbaum.org/till/i2c_tiny_usb


The firmware code itself is distributed under the GPL, but
one of the usb codes comes under a separate license. Plase see 
the .txt files in usbdrv for details.

The default configuration is for a attiny45. The Makefile.mega8
allows to compile the device for the Atmega8 cpu. This includes
the possibility to use the atmega8 rs232 for debugging.

The attiny45 has to be programmed in high voltage serial 
programming (hsvp) mode since this application needs the
reset pin to be reconfigured for other use.


On tinyusbboard debugging is off by default.
Also there is no fusing neccessary, since usbtiny can be txed
via USBaspLoader bootloader directly (without external programer).


This project supports multiple usb implementations: The avrusb,
usbtiny and various tinyUSBboards. Due to this these Makefiles exist:

Makefile-avrusb.tiny45            - build with avrusb for Attiny45
Makefile-avrusb.mega8             - build with avrusb for Atmega8
Makefile-usbtiny.tiny45           - build with usbtiny for Attiny45
Makefile-usbtiny.mega8            - build with usbtiny for Atmega8
Makefile-tinyusbboard20M.mega328p - build with usbtiny on 20MHz tinyusbboard with atmega328p
Makefile-tinyusbboard.mega328p    - build with usbtiny on 16MHz tinyusbboard with atmega328p
Makefile-tinyusbboard20M.mega168p - build with usbtiny on 20MHz tinyusbboard with atmega168p
Makefile-tinyusbboard.mega168p    - build with usbtiny on 16MHz tinyusbboard with atmega168p
Makefile-tinyusbboard20M.mega88p  - build with usbtiny on 20MHz tinyusbboard with atmega88p
Makefile-tinyusbboard.mega88p     - build with usbtiny on 16MHz tinyusbboard with atmega88p
Makefile-tinyusbboard.mega8       - build with usbtiny on classical 16MHz tinyusbboard

Just type 
 make -f Makefile-avrusb.xxx program
or
 make -f Makefile-usbtiny.xxx flash
or
 make -f Makefile-tinyusbboard.xxx program


to compile and upload the file. Please adjust e.g. programmer
settings in the Makefile.

If you don't want to recompile the firmware yourself you might
use the included firmware.hex which is a prebuilt binary for the
attiny45. Plase make sure you adjust the fuses accordingly.
They need to be set to "external crystal > 8Mhz" and the RESET
pin has to be disabled in order to be re-used for application
specific purposes. See Makefile-avrusb.tiny45 for more details.