Jaguars not passing CAN communications

[Alan Anderson]

Rule of thumb: When you have a problem on a CAN bus, look for a termination issue at the other end of the chain from where the problem manifests itself. If the first couple of Jaguars work but any farther ones do not, check the termination at the end closest to the cRIO.

[jwakeman]

I have four black jaguars i want to include in my network. Right now I can only see one jaguar at a time. I am able to communicate with all four Jaguars individually but if I try to chain two together i only see the first in the chain.

Originally Posted by linuxboy

Hi all,
So I made a post a while ago about only seeing the first Jaguar in the chain.

Can you post a link for that thread here? It may be helpful to me.

Originally Posted by Alan Anderson

Rule of thumb: When you have a problem on a CAN bus, look for a termination issue at the other end of the chain from where the problem manifests itself. If the first couple of Jaguars work but any farther ones do not, check the termination at the end closest to the cRIO.

I made the cable to connect the rs232 port to the first black Jag. I included the terminating resistor in the CAN plug end of the cable instead of in the RS-232 plug. The cable is probably 2 or 3 feet long. Do you think this could be causing the issue i described above? I can explain my cable construction more clearly if required..

[linuxboy]

Hi,
Here is the old thread, I don't know that it ever got resolved.

You need a terminating resistor on both ends of the cable (the serial port end and the terminator end).

I managed to get it working by remaking the DB9 connector a couple times. I highly recommend this tutorial on it as it is pretty easy to understand.

Oliver

[jwakeman]

Originally Posted by linuxboy

You need a terminating resistor on both ends of the cable (the serial port end and the terminator end).

The following is from the MDL-BDC-24 - Getting Started Guide:

RS232 Cable Assembly
Follow these steps to complete cable assembly (shown in Figure A-4):
1. Take the Modular Adapter and cut the black wire as short as possible. This wire is unused.
2. Cut off the terminals on the Red and Green wires. Strip then solder the Red and Green wires
to the 100 resistor. Use a section of heat shrink to protect the resistor and solder connections.
3. Insert remaining terminals into the DB9 receptacle. Pin numbers are indicated on the plastic
connector body.
– WhitePin 3
– Blue2
– YellowPin 5
4. Slide the back-shell over the connector, then insert the modular cable to complete the
assembly.

This sounds like they only expect 1 terminating restistor to be part of the RS232 - CAN cable, at the RS232 end. I looked at the guide you linked to and it does seem they expect a resistor at each end of the cable..seems like a conflict here but the "Getting Started Guide" does look more official to me. I attached this document. I guess it makes sense that this cable should only contain one resistor. If i understand correctly you want one resistor at each end of your network. If this cable contains two resistors it seems you would end up with three total resistors once you add one at the tail end of you daisy chain..

[FrankJ]

Terminating resistor has nothing to do with the RS232 bus. It terminates the RS422 bus that is in the same plug. The other terminating resistor is in the unused port on the last Jag in the daisy chain (making a total of 2). The bus will mostly run without the terminating resisters, but will be subject to noise. It will also be the first troubleshooting question.

I found to get all the Jags to communicate that I had to power up the jags with them all connected & then restart the BCD-COMM com. A little concerning because it seems to me that the new jags should be recognized as they are plugged in.

[linuxboy]

Originally Posted by FrankJ

I found to get all the Jags to communicate that I had to power up the jags with them all connected & then restart the BCD-COMM com. A little concerning because it seems to me that the new jags should be recognized as they are plugged in.

This is something I noticed as well that I forgot to mention. It seems like some of the time hotplugging works, and other times, it does not, and you need to power on all the Jags at the same time. I don't know if that really is necessary, but its worth a shot.

Oliver

[taichichuan]

Probably restating the obvious here, but make sure that you reprogram the CAN IDs on the Jags before plugging them into the bus. By default, the Jags all come with the same ID set. So, even if the termination is correct, you'll only see one of them. You can reprogram the IDs using the BDC_COMM application. Follow the getting started guide for details. BTW, you can get a complete set of working CAN cables w/ terminators and the RS-232 cable from http://www.estoprobotics.com/estore/ if you're interested.

HTH,

Mike

[jwakeman]

Originally Posted by taichichuan

BTW, you can get a complete set of working CAN cables w/ terminators and the RS-232 cable from http://www.estoprobotics.com/estore/ if you're interested.

Yes! I will be buying a couple of those starter packs. I would like to think i am capable of making the cables myself but at this point I just want to take some of the mystery out of this and using cables that i can reasonably assume are proper will go along way towards maintaining my sanity!

[jwakeman]

Originally Posted by jwakeman

Yes! I will be buying a couple of those starter packs. I would like to think i am capable of making the cables myself but at this point I just want to take some of the mystery out of this and using cables that i can reasonably assume are proper will go along way towards maintaining my sanity!

We got the cables from e-stop electronics. Unfortunately, I am still seeing some flakiness in the CAN network. I have successfully had all four nodes on the network at once but it is still not reliable. I am looking for some specific diagnostics steps I can perform. I suspect it could be noisy/poor power supply, grounding issues, cable issues (even though i bought them). Armed with a oscilloscope and multimeter are their specific measurements i can make to look for termination/noise issues? Thanks!

[Mike Copioli]

Originally Posted by jwakeman

We got the cables from e-stop electronics. Unfortunately, I am still seeing some flakiness in the CAN network. I have successfully had all four nodes on the network at once but it is still not reliable. I am looking for some specific diagnostics steps I can perform. I suspect it could be noisy/poor power supply, grounding issues, cable issues (even though i bought them). Armed with a oscilloscope and multimeter are their specific measurements i can make to look for termination/noise issues? Thanks!

Do you have access to a 2CAN? If you do you may use it to help diagnose the problem. An o-scope will not tell you much unless you know how CAN operates, the 2CAN however can diagnose if your CAN connectivity is the issue.

[jwakeman]

I don't have one yet but I am trying to get one. What kind of diagnostics does it provide? It would give me some kind of indication of the quality of the network?


Also, other suggestions please in case I don't get the 2CAN for a few weeks.

[Mike Copioli]

Originally Posted by jwakeman

I don't have one yet but I am trying to get one. What kind of diagnostics does it provide? It would give me some kind of indication of the quality of the network?.

The 2CAN LED will tell you if you have good CAN connectivity and whether or not you are communicating with the plugin on the crio (Ethernet connectivity). The web dash will show information on each Jaguar on the bus such as voltage, current, ID, temperature and throttle and allows firmware to be loaded onto the Jags.

In the mean time check your cabling, reduce your number of Jags on the BUS down to 1 until you are successful (I see you have already done this but this reduces the possibility that you have more than one jag on the bus with the same ID.) And yes the CAN bus will not operate without at least one 120 ohm termination resistor, although the BUS will work with only one you should have both in place at each end of the BUS as this is what CAN is designed around. If you are using 100 ohms that is fine as well. Even though the CAN spec and the TI data sheet for the CAN PHY both say it should be 120 ohms, using a 100 ohm resistor will probably work fine. Make sure you are not trying to write to Jags that are not present on the BUS as this will cause you pain and the -44087 timeout error.

I hope this helps.