I recently purchased a couple of Inland (Microcenter) CAN Bus shields, and while coming up to speed with them I noticed that the MCP2515’s interrupt pin is tied to pin 8 of the Arduino UNO instead of 2 or 3. Anyone know why? It seems that the correct pin would be the UNO’s pin 2 or 3. I jumped pin 8 to pin 2 (INT0) and it works just fine using interrupts, but, I’m wondering why 8?
I’m probably going to cut the trace going to 8 and run a wire to either 2 or 3. But before I do, I’m wondering if there’s a reason that I’m missing.
It depends if you are going to run it as interrupt driven or polled. When polled any input pin is OK but when interrupts you need to use a pin that supports interrupts. Look at the code. With out links to the hardware technical specifications this is my best guess.
Thanks for the reply. Yes, I understand all that. I guess my question was, is there an actual reason for the MCP2515’s interrupt line being connected to digital input 8 (which would be somewhat a pain to code as an interrupt so as not interfere with the SPI pins on digital inputs 11, 12, and 13) versus connecting it to digital pins 2 or 3 which are normal interrupt pins and would seem to be the easiest thing to do. Or is it just that whoever designed this board maybe wasn’t paying attention that day.
Like I said in my original post, I jumped digital 8 to digital 2 and it works just fine using interrupt 0, and I plan on cutting the trace going to 8 and run a wire from the device’s interrupt line to either digital 2 or 3 of the shield.
That sounds correct, Pin 2 or 3 support interrupts, pin does not. Also it could be polled depending on the software. Some people love interrupts, others do not. Most of the time it is personal preference or performance issues.