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HUB ISP - Solving the USB-Only “Chicken or Egg” Problem

Not For Beginners, or Anyone Who Values Their Time
If you are just getting started with AVR microcontrollers, ISP programming is not a good place to begin, even if you buy a ready made programmer, and certainly not by trying to build your own!

Ready-to-use boards like Teensy (yes, a shameless plug, as I make this one) or Arduino just plug into any USB port and are ready to go, with easy to use software tools. Troubleshooting electronics and software can be taxing even for experienced engineers, so it's highly recommended to start with a foundation that's as trouble-free as possible. HUB ISP is, well... not.

HUB ISP is certainly not a viable replacement for regular "chicken or egg" AVR ISP programmers, which are much faster and more reliable, and maybe even cheaper... eg, Teensy running the ArduinoISP code (yup, another shameless plug).

However, if you love to tinker or you're just curious how this could possibly work with only USB and no programmable chip, without even any parts designed for USB, only logic gates and resistors, then read on!

[Source] Hackaday.com via PJRC