Is it possible to use interrupts to read the Pololu QTR-xRC or QTR-xA reflectance sensors?
For the RC, you charge the capacitors, enable pin change interrupts for all the channels, set a counter to 0, and then read the counter each time the pin change interrupt fires (and you poll which pins have changed level since last time.)
For the A version, if you only need “yes no” answers, you need to threshold the on/off level appropriately. Either it works, or it doesn’t. With proper thresholding, you don’t even need interrupts; you can just read the pins that it’s connected to as a “yes” or "no."
To be able to adjust the threshold, you may want to drive the LEDs with PWM and a RC filter, or re-buffer with opamps (one per channel!)
Thanks! I’ll give it a try.