I have worked w/ Tiny's and V-USB before. USB D+ needs to be connected to PB2 (INT0), any other PB pin will do for D-. The
HID Keys project is a good example on how to wire up the USB port (and run the Tiny at 3.6V, saves the Z-diodes.) V-USB works best w/ an external crystal oscillator, but it does contain some code trying to make do w/ the internal RC clock by "overclocking" it to 12.8 MHz. This may or may not work w/ the 85.
General Description:
This file is the 12.8 MHz version of the USB driver. It is intended for use with the internal RC oscillator. Although 12.8 MHz is outside the guaranteed calibration range of the oscillator, almost all AVRs can reach this frequency. This version contains a phase locked loop in the receiver routine to cope with slight clock rate deviations of up to +/- 1%.
See usbdrv.h for a description of the entire driver.
LIMITATIONS
===========
Although it may seem very handy to save the crystal and use the internal RC oscillator of the CPU, this method (and this module) has some serious limitations:
(1) The guaranteed calibration range of the oscillator is only 8.1 MHz. They typical range is 14.5 MHz and most AVRs can actually reach this rate.
(2) Writing EEPROM and Flash may be unreliable (short data lifetime) since the write procedure is timed from the RC oscillator.
(3) End Of Packet detection (SE0) should be in bit 1, bit it is only checked if bits 0 and 1 both read as 0 on D- and D+ read as 0 in the middle. This may cause problems with old hubs which delay SE0 by up to one cycle.
(4) Code size is much larger than that of the other modules.
As for a bootloader, Tiny's don't support a bootsection, making a BL a major PITA. Atmel has some writeup on this topic,
Atmel AVR112: TWI Bootloader for Devices without Boot Section.
I own an AVR ISP mkII and have access to a jtag ICE mkII at work, so I can help w/ getting prototypes going. PM me if interested.
Edit: firmware wise it probably would be much easier to use a 90USB162 or Mega16U2...
