Neo and Spark Maxes not getting signal over CAN

We have Neo’s hooked up over CAN and we have no signal, all of them are running the latest firmware. All of them are plugged in correctly and our Victor SP’s are all working. And our PCM and PDP are communicating in the same CAN loop as the Neo’s.

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@dyanoshak Any ideas?

Is CAN a serial chain, star, or mix?
Did you use the CAN pig-tail that came with the SparkMax?
Do you have any points where you have CanH and CanL crossed?
Yellow to Green and Green to Yellow
Power off - if you measure resistance across CanH to CanL do you get 60 Ohms?

It is running in serial and is getting 116-117 Ohms. CanH and CanL never cross and we used the CAN pigtail

CAN should be terminated on each end with a 120 Ohm resistor.
That’s why you should get 60 Ohms.
The RoboRio is one termination, PDP can be the other.
Are each of these at opposite ends?
Check the jumper on the PDP to make sure the termination resistor is in.

yes the PDP is at one end with the RoboRio at the other, and the termination resistor on the PDP is set to on.

What blink pattern is the LED on the Spark showing?

There is also the possibility that the pig tail is not completely seated at one of the SparkMaxes. Are you sure that these connectors are fully seated?
Is the RoboRio able to see the PDP across CAN?

4 are flashing magenta, 4 are flashing cyan (yes they are suppose to be split)

Both the PDP and PCM are visible over CAN

The RoboRio, by iteslf, provides 120 Ohm termination.
The PDP, jumpered on, provides a second 120 Ohm termination.
The two in parallel should indicate 60 Ohms.
And yet you are able to talk across the bus from start to end.
I’m still not convinced that you don’t have a hardware problem.

I think Carlos is considering SparkMax configuration … pursue that for a while.

To confirm, the PDP is supposed to be at one end of the CAN run, the RoboRIO is supposed to be at the other?

Check CAN ids?

Checking in on this thread (thanks for the ping @rlounds).

In addition to the good suggestions from everyone else in the thread, double check that the APIs have been updated to the latest versions. Earlier APIs are not compatible with the most current firmware versions.

As of last week, the latest API and firmware version is 1.4.0.

If you’re still having trouble, feel free to send us an email at!

Rio and PDP at opposite ends is not required.
If you are using both as termination devices, then I would recommend this configuration - all devices should be between the termination resistors.

If they are at opposite ends, and you can communicate with the PDP from the Rio, that says a lot for the CAN bus configuration.

Make sense?