Porting V-USB to Atmega48 / 88 / 168 - important hint

hendrix13 · Post by **hendrix13** » Sun Jun 19, 2011 4:10 pm

I run into problems with porting HIDKeys and some other projects from ATmega8 to ATmega48 and could not succeed with hints from other posters. I finaly solved the problem with some important changes at the end of usbconfig.h. The trick was:

Code: Select all

#define USB_INTR_CFG           EICRA /*  not   MCUCR */
/* #define USB_INTR_CFG_SET        ((1 << ISC00) | (1 << ISC01)) */
/* #define USB_INTR_CFG_CLR           0 */
 #define USB_INTR_ENABLE        EIMSK   /* not    GIMSK */
/* #define USB_INTR_ENABLE_BIT        INT0 */
 #define USB_INTR_PENDING        EIFR    /* not     GIFR */
/* #define USB_INTR_PENDING_BIT       INTF0 */

ATMEL changed some register names with Atmega48/88/168, so V-USB needs these changes to let the driver enable external interrupt INT0. Wondering why I got no error messages before changing this like for TCCR0 and TIFR (has to be TCCR0B and TIFR0). My Atmega48 works fine with 12 MHz, 5 V from USB and 68 Ohm / 3,6V zener diodes at the data lines.

Of course don´t forget to uncheck the CLKDIV8-fuse and it is a good idea to use the latest usbdrv from 11-2008 even with the older projects.