Which pins pass through to Arduino?


I’m sure this will seem really basic and obvious, but it isn’t (yet) to me. I’d appreciate some guidance.

I have an Arduino Uno and a Seeed CAN Bus Shield V2.0 (https://wiki.seeedstudio.com/CAN-BUS_Shield_V2.0/#schematic-online-viewer)

I would like to pass through some signals (buttons, LEDs, etc.), but confess that I’m not understanding what I’m seeing on the schematic. Things like MISO, MOSI, SCL, SDA, and SCK all look like they are used by the shield, so would that leave IO7 - IO4 available? Have I an reasonable understanding? Yes, I could (and will) also try it to see if it works, but I’d appreciate some pointers on interpreting the schematic.

Thanks so very much for your time and assistance.

Hi @PDP, In the board file we can simply see that, please check and let me know your thoughts on this :slightly_smiling_face::+1:

Hi Salman;

Thanks so much for your response. May I verify that any pin that isn’t explicitly routed to an IC on the shield is being passed through? Here we see digital pins 0, 1, 8 don’t have any connections and the same is true for analog pins 2 - 5 (along with ground pins). Therefore, those pins are available to pass directly through – yes?


It should be, I don’t have the Seeed CAN Bus Shield right now if you have one try to check the continuity with the pins.

Hi Salman;

Took me a while before I could come back to this. All of the pins have continuity between the header and pins, so it looks like the board file is the way to go.

Many thanks,


Hi @PDP, Glad to know that :slightly_smiling_face::+1:.