Black Jaguar CAN Issues

[jngleofinsanity]

Hey there,

We have run into an interesting problem. We had an old testboard with one black Jaguar serving as an RS232 gateway to CAN from the cRIO, and daisy chained to several Grey Jaguars working just fine. But when we shifted to our actual electrical board, with only Black Jaguars daisy chained to each other (and all flashed correctly with the v89 Firmware and different ID's), our programmers could not get a response from any jaguar but the initiating one. We swapped out both Jaguars and cables in an effort to solve the issue, but to no avail. Running our Jaguars over CAN is crucial to us since we want to wire our encoders directly into them.

Does anyone have some advice as to how we can solve this issue?

Thanks
--Jay

[Radical Pi]

What do you mean by no response? No actuation? Yellow blinking lights?

Does the bus work through BDC-comm?

Are you using the camera right now? If the camera is still booting while trying to use the CAN bus the system gets a little messed up. Once the camera finishes booting it should work normally again

[jngleofinsanity]

Thanks for the quick response!

We see yellow blinking lights, and we told the cRIO to give a bit of text in the readout for each jaguar it managed to access, but it only gave it off for the first one each time.

Apparently, the bus works through BDC-COMM

And no, as of right now we are not using the Camera, but we hope to implement it in the near future. Any additional tips on that front?

[Mark McLeod]

How do you have the Black Jaguar ports chained?
RS232 port-RS232 port CAN port-CAN port ?

[jngleofinsanity]

Wait, I'm not sure whether or not I actually "daisy-chained" them correctly

The wires go from RS232 on the cRIO to RS232-to-CAN on Black Jaguar, then from CAN on one jaguar to the open RS232-to-CAN on Black Jaguar #2, and from the CAN port on that jaguar to the open RS232-to-CAN on Black Jaguar #3, so on and so forth.

Is it supposed to go CAN-CAN-CAN-CAN (only reason this would've worked on grey jags then is because they're all CAN ports)? Or RS232-RS232-RS232-RS232? And doesn't that mean you need to mash more than one RJ11 cable into the same crimp?

[Mark McLeod]

You see the problem. This is a CAN-bus we're dealing with, not an alternating CAN/RS232 hybrid. A CAN-port won't talk to an RS232-port of course, they speak different languages.

The Black Jaguars are intended only as a converter from RS232 to CAN at the start of an uninterrupted CAN bus, they don't have enough CAN ports to form a traditional CAN daisy chain, only the Gray's have the CAN ports to continue a daisy chain.

You'd have to try a different style of CAN bus using what's called vampire taps, where you have a continuous CAN cable with splices for side cables split off to feed your Black Jags. You still need to terminate the cable with a 100 ohm resistor. This is essentially what the Gray Jags are actually doing, just internally. I haven't tried running a continuous outside cable for a string of Black Jags myself though.

You might be able to chain two Black Jags together the prescribed FRC way, as long as you terminate the 2nd Jag's RS232 port with a 100ohm resister, the same way you terminated the first RS232 cable. But I haven't tried this either.

[Radical Pi]

You see the problem. This is a CAN-bus we're dealing with, not an alternating CAN/RS232 hybrid. A CAN-port won't talk to an RS232-port of course, they speak different languages.

The Black Jaguars are intended only as a converter from RS232 to CAN at the start of an uninterrupted CAN bus, they don't have enough CAN ports to form a traditional CAN daisy chain, only the Gray's have the CAN ports to continue a daisy chain.

That's not quite true. While CAN and RS232 are completely different, the wires for them are also completely different. If you put together the RS232 to CAN adapter, you put a resistor between the Red and Green wires. Those are the 2 CAN wires. All the other ones plugged into the DB-9 connector are the Serial wires. As long as the CAN to CAN cables were assembled properly (double check that btw), 2 Black Jags should be able to be on the same bus.

Also, try messing with your configuration. Change the order of jags daisy-chained, try a different jag as the serial to CAN, swap around cables. You might have happened to put a bad connection between the source black jag and the 2nd one, breaking the bus

[dyanoshak]

On a Gray Jag the two ports are both 6-position 4-conductor (6p4c) modular plugs. On a Black Jag the left port is 6p6c and the right port is 6p4c. The extra two conductors on the left port are serial lines. This means the left port on the Black Jag is dual function, and can be daisy chained like the Gray Jags in the CAN-only part of the network.

[EricVanWyk]

I found the "enumerate" function to be really helpful for this sort of stuff. I don't have LV in front of me at the moment, but this command will tell you what IDs it sees on the CAN bus at the moment. I just stick it in a slow (5 second?) loop and have an indicator hooked to the output.

This will give you a better idea of what is going on.

[taichichuan]

Hi Gang,

When I run into these sorts of problems, it's almost always related to bus termination. The approach of putting the terminator into the RJ-12 is simply too prone to shorting out. It's best to run a short length of wire out of the RJ-12 and solder the terminator externally w/ some heat shrink to keep it safe.

HTH,

Mike

[movax]

I can't stress enough the importance of a termination resistor on the bus. Without the proper termination, you will get nasty signal reflection on fast edges and that will result in error frames/communication errors.

If you remember SCSI drives, that is why a terminator was necessary on SCSI cabling as well.