Model of AVR controlled power supply. 8 bit input represents one port of atmega32. Comparator is provided by build-in AD converter operating in 8 bit mode and the output voltage is set in software part. The value of the port register is being increased until the output voltage measured by ADC reaches the preseted value. It can be easily configured in upto 30 bit, providing superior resolution, but then you should use two pins for compararor as the max res of the ADC in atmega32 is 10 bit and then increment the 30 bit value until it compares. Also you can add some sort of adaptive delta ( double the increment for reaching the value quicker ) in your code to help it to react to rapid changes of the reference quicker. This way you can build yourself a sophisticated bench supply with voltmeter and ammeter using microcontroller. There is a noticeable output noise which is caused by constant oscillations around desired output values, there is simply no room to add a circuitry to stop counting when close to wished value.
