A Nano or Pro Mini board only has 2 interrupt pins, I need more but cannot switch to different board. I want the micro controller to run the same sequence any time one of 3-5 sensors goes high and triggers and interrupt. The Nano/Pro Mini doesn't need to know which sensor went HIGH. Can I put a two input OR gate in front of each interrupt pin to essentially get 4 interrupt pins, or is there a better way to do this with these boards?
The first question is whether you need to use interrupts at all. What is the Arduino doing apart from reacting to the sensor inputs ? What type of sensors are they ? Have you heard of pin change interrupts ?
I have the Arduino sleeping and I want it to wake and run a routine when motion is sensed from one of the PIR sensors. Everything is on battery so I need to sleep to conserve power. I have not heard of pin change interrupts but will look them up. Is there any reason why an OR gate would be a bad idea?
The Nano is essentially identical to the UNO and the Pro Mini just the same without a USB interface. What makes you think there is a limit to two interrupt pins?
Of course you could use a gate, but you almost certainly do not need it.
Maybe I’m reading this wrong but according to the technical specs page here:
Which has a table that says: “External Interrupts: 2”
Below the page says:
“External Interrupts: 2 and 3. These pins can be configured to trigger an interrupt on a low value, a rising or falling edge, or a change in value.”
Look at pin change interrupt, there are a couple of them.
Roughly speaking "external interrupt" has more features than simpler "pin change interrupt".
Using an OR gate is surely possible if you want to save pins/wires. You can also use a wired-OR with diodes (or directly if the PIR outputs are open drain). One day you may decide it is important which sensor was triggered. You won't be able to implement it by a simple code change.