Do you really have an USBtinyISP device as you specified on the command line? If yes, it will probably not be on /dev/ttyusb4, as it doesn't emulate a serial interface. The USBtinyISP are access through libusb and not by a kernel driver.
Do you really have an USBtinyISP device as you specified on the command line? If yes, it will probably not be on /dev/ttyusb4, as it doesn't emulate a serial interface. The USBtinyISP are access through libusb and not by a kernel driver.