Another thing we need to change in the makefile is to set mcu/part code to attiny85 for both avrdude and gcc. Furthermore, F_CPU can be set in the Makefile by passing -DF_CPU=16500000 as a command-line argument to gcc, so defining it can also be omitted from main.c. Note that USB_CFG_CLOCK_KHZ now relies on F_CPU constant. Add the following after USB_RESET_HOOKĮxtern void hadUsbReset(void) // define the function for usbdrv.c

#define USB_RESET_HOOK(resetStarts) if(!resetStarts) #define USB_CFG_HAVE_MEASURE_FRAME_LENGTH 1 Here are the changes I made to usbconfig.h: Also, the oscillator calibration routine needs a hook added to the config. Main code changes needed are the change of pins to PORTB. Note: 2.2 kohm pullup for D- was missing in the schematic, it has now been corrected. Note that due to the angle it can seem like the 0.1 uF tantalum cap (light brown one) is wired to PB4 when it really is going to GND pin! Here’s the schematic, heavily borrowed from V-USB’s EasyLogger reference implementation:

In the photo, I used a 4-pin header to show the place of the USB cable so the zener diodes would not get obstructed. I challenge anyone to drastically shorten these wire runs! ATtiny45 and ATtiny85 are smaller than ATtiny2313 and have an internal oscillator that can be calibrated to provide 16.5 MHz clock, accurate enough for V-USB to do its magic. So I thought I’d build upon the part 4 of the tutorial but modify the setup a bit to run the AVR at 5 volts and use zener diodes to drop D+/D- voltage, thus eliminating the need for a regulator. One guy at Hack a Day remarked on the long wire runs in my V-USB tutorial breadboard setup.

Attiny85 serial port