I have created a bunch of circuit boards that use Nano 3.0 and don't have access to pin 2 and 3 anymore. The board has access to Analog Input 0 and 1 for generic inputs, and I'd like to use Analog 0 for a interrupt. The application is triggering of an LED light source. A TTL low signal is sent simultaneously to a digital camera and to my circuit board for synchronized camera-LED shuttering, so I need to respond as quickly as possible to stay in sync with the camera.
1) Does it take longer to execute a pin-change interrupt compared to an external interrupt on pin 2 or 3?
2) Can you create a conditional interrupt when the pin input goes low on a pin-change interrupt like you can with external interrupts? The Arduino site says no, but I've seen a post that describes code to do it. What is the best way to achieve this, and how much clock time would I loose?
Thanks for your response.