Pixhawk 2.1 CAN Bus Limits

PX4 Autopilot Flight Controllers 💻
1

Hello,

Is there a maximum current that the Pixhawk 2.1 CAN bus will output?

I have connected multiple UAVCAN nodes (UC4H) and everything works great while I have the network connected to the computer (via Babel). However, when I try to run everything with just the Pixhawk and my CAN nodes, the Pixhawk doesn’t make it all the way through the boot cycle. It works fine when I have only 10 of these nodes, but after 10, the Pixhawk crashes.

I am thinking that the UC4H nodes might be drawing too much current from the Pixhawk on the CAN power line causing it to crash. Does this seem probable to anyone else? If not, do you have any other ideas what could be causing the Pixhawk to crash?

Thanks,

Jon

2

Olli mentions this in his blog somewhere: if you’re running a lot of nodes and powering them off the bus (particularly if you have notification nodes), you need a separate Bec.

3

Thanks auturgy. I disconnected the power and ground lines from the CAN cable coming from the Pixhawk, so it only sees the data lines. Unfortunately, I am still having the same problem where the Pixhawk crashes on boot when more than 10 nodes are connected. Is there some other place that might be limited to having 10 nodes connected? Maybe this is a question for @PavelKirienko .

Thanks,
Jon

4

Nothing comes to mind. I think you could put some breakpoints and try to debug that?

5

I’d suggest first step is connecting to the nsh console and seeing what is happening as it boots.
Then break points if needed, but the console might have enough info.

6

Maybe this is a dumb question, but how do I do that? I know how to connect to the nsh console once the Pixhawk is booted up, but I have not been successful in monitoring boot. Is this done through the micro-usb port on the side? I found this article, but was unable to see anything. I forgot to mention that this is a Pixhawk 2.1. I wired the FTDI cable to the USB port (where the buzzer gets plugged in). Is this the right place to be trying to debug?

Thanks,

Jon

7

It’s marked CONS, with a 3 pin header (no 5v line to it). I can’t remember the pin order, but connect the ftdi to CONS, then power up over USB or battery.

8

Found it. Thank you very much! The problem turned out to be a faulty CAN node. I’m not sure whats wrong with it, but when I connect it to the pixhawk, the pixhawk crashes. Im just going to scrap it and build a new one.

Thanks for your help!

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