Modern PCs rarely have a serial or parallel port any more, to the great regret of any-one who experiments with microcontrollers every now and then. In the old days it was very simple to use the parallel port of a standard PC and program just about any type of AVR microcontroller with it. When you want to do that now, you’re first obliged to buy a programmer that communicates with the PC via USB, which immediately raises the threshold of getting started with these microcontrollers. The circuit presented here offers a solution to this. Simple USB AVR-ISP Compatible Programmer Circuit Diagram : As you can see from the schematic, this is a very simple circuit, built around a cheap, standard AVR microcontroller plus a handful of passive components. You may have already observed that this microcontroller does not have a USB interface and the circuit does not use a USB to serial converter either. The strength of this circuit is found in the firmware. The USB interface has bee...