Arduino MKR CAN Shield Review - part 1: Log BUS Traffic

RE: Arduino MKR CAN Shield Review - part 1: Log BUS Traffic

Jan Cumps — Tue, 25 Jun 2019 09:22:33 GMT

I've been testing Sandeep Mistry's CAN library further. It supports interrupts with CAN receive, and hardware filtering.

The interrupt functionality works nicely. You can make the Arduino sleep, and the CAN device will wake it up when receiving data..

I have difficulties with the filter though. The CAN controller (Microchip MCP2515) allows you to set a filter.

When you do that, the microcontroller is only contacted when there's a message that it is interested in.

On a CAN bus, where there can be a lot of traffic, this is useful. You don't have to triage through noise to find the data that's intended for you.

But (further investigation needed) the library does not work as I expect it. It sets the filter registers of the CAN chip but the scope of the filter doesn't seem to match the API.

I am trying now on lower level, setting the registers in my own code, and that gives the expected results.

If it turns out to be a bug in the library, I'll fork it on github, try to fix it and contribute back to the original lib as a pull request.

If it is my understanding of the lib that's wrong (a more likely scenario), I'll post back on it here.

RE: Arduino MKR CAN Shield Review - part 1: Log BUS Traffic

gam3t3ch — Wed, 19 Jun 2019 00:46:50 GMT

Great stuff thanks for sharing!

RE: Arduino MKR CAN Shield Review - part 1: Log BUS Traffic

Jan Cumps — Tue, 18 Jun 2019 20:44:26 GMT

The example here is useful to stream everything published on a bus.

When you're implementing a real can device, it's worth checking out the library API for the filter function.

This functionality tells the CAN device to only react to agreed messages. Hardware is filtering messages for you. It takes care that the microcontroller never has to react on (or wake up on) non-relevant packages.