The targetc is target-count. I am incrementing a counter each time the rising-edge interrupt happens. counter is incremented in the interrupt handling routing and compared to the target-count inside the IHR. I am assuming the counter is only incremented once per rising edge, and that rising edges are reliably detected by the ESP32 hardware. I expect these rising edges to happen at a rate of 30 to 350 times per second. See my next post below for a related question on the IHR.