Implement communication from arduino to Pi

[rwilbur]

We need to figure out if this is going to use UART or SPI

[lee-matthews]

I'm wondering which one is more noise redundant and whether ground voltage differences could pose an issue. Maybe not given cable length. I was thinking of a differential link (RS485/LVDS) but this would increase the complexity a bit and the number of components required. Maybe UART could give us the necessary speed, do you know how fast the UART can go on this Arduino?

[rwilbur]

Looking at the clock rate and from what people have said online it appears to be capable of 2Mbps. I agree the differential UART link would be nice to have because of the robustness to noise. I have used RS232 in quite noisy environments and have never had noise issues with it so in practice it might be perfectly acceptable. I think the fewer the parts the better.

[lee-matthews]

I presume the Arduino only has a UART output (0 to 3.3V) instead of +-12V? To add RS232, we may need to add an extra module anyway, a MAX232 perhaps? Maybe these come in premade modules for rpi / arduino.

[rwilbur]

I meant 3.3v when I said 232 but that is incorrect. I think the 3.3v UART would probably be fine. The UART on the PI is also 3.3v so they should play nicely together. If these 2 devices are super close together we can probably do a good job keeping noise down by just having a super connection.