I have some problem. I think my UsbAsp is old because it say when uploadin sketches "Impossible to set SCK, Update UsbAsp Firmware".
So my problem is that UsbAsp could upload only the bootloader. When I program the bootloader all is ok, only sometimes it say that my ATMega 2560 have a bad signature.
But when I upload whatever sketch with UsbAsp, to the ATMega 2560 like Blink example, the led doesn't flash.
If I burn the bootloader with UsbAsp the led flashes for the bootloader. Then if I burn the blink sketch with the standard USB/Serial programmer integrated in the arduino all is ok and the led flashes with different timings.
It seems that UsbAsp could program only the bootloader! :'(
I need in my sketch all 4 serial ports, how could I do? Do you think that Arduino ISP is better for ATMega 2560? Or I'm missing something related with my hardware?