usbasp improved

USBasp firmware based on <a href="https://github.com/bperrybap/usbasp">a fork by Bill Perry</a> and the latest <a href="https://github.com/obdev/v-usb">v-usb</a>.

Firmware version 1.06 (2020-09-14) features a default SCK clock of 1.5Mhz and automatic SCK slowing if target does not respond. PORTD is left as input, so this firmware also works <a href="https://www.sciencetronics.com/greenphotons/?p=938">with USBISP modules</a>.

Thanks to <a href="https://github.com/nerdralph/usbasp/pull/5">patches from Dimitrios</a>, the USBasp firmware 1.08 is WCID compliant, meaning it should work on Windows without any driver or .inf install.

A pre-built hex file for the mega8 (main.hex) is in the firmware directory, along with m88.hex for the mega88.

development plans

Recognize when the target device is in debugWIRE mode, and send the dW command to enter ISP mode.