Can't enumerate the entire bus

[linuxboy]

Hi all,
Last night I finally got CAN working reliably (or so I thought). This morning I came in and decided to write code for using the Jags on the cRIO instead of just using BDC-COMM. Somewhere when testing I started to get errors about a firmware version being 0. I connected it to BDC-COMM again and found that it wasn't enumerating the second jag on the bus. I switched the order that the Jags were wired and it recognized the one that became the first Jag after the switch (the one that wasn't getting enumerated before). Then I tried using 3 Jags and was able to (unreliably) read the second but not the last jag in the chain.

Any ideas guys?

Thanks

[taichichuan]

Hmm... This sounds like cabling and/or termination problems. Make sure that your terminators haven't shorted out. The picture that has you putting the 100 Ohm resistor in the RJ-12 jack is misleading. If you use that approach, it's real easy to bend the resistor leads and short them out leading to a lot of CAN weirdness.

I typically create a small pigtail coming out of the RJ-12 and solder the terminator resistor to that and insulate it w/ some heat shrink. I also put the terminator resistor in the DB9 shell (run 6C wire from the RJ-12 to the DB9 and put the terminator in the shell where it's protected). That approach has lead to very solid CAN performance.

HTH,

Mike

[linuxboy]

Originally Posted by taichichuan

Hmm... This sounds like cabling and/or termination problems. Make sure that your terminators haven't shorted out. The picture that has you putting the 100 Ohm resistor in the RJ-12 jack is misleading. If you use that approach, it's real easy to bend the resistor leads and short them out leading to a lot of CAN weirdness.

I typically create a small pigtail coming out of the RJ-12 and solder the terminator resistor to that and insulate it w/ some heat shrink. I also put the terminator resistor in the DB9 shell (run 6C wire from the RJ-12 to the DB9 and put the terminator in the shell where it's protected). That approach has lead to very solid CAN performance.

HTH,

Mike

I use the wires to make a terminator plug approach as well. I also made another one just to be sure. The only thing I haven't swapped out is the DB9 to rj12 connector although I tested it with a multimeter and the resistance on the middle two pins seems fine as well as the continuity between the proper serial and RJ12 pins. I'm pretty stumped.
Oliver

[Hugh Meyer]

Be absolutely sure you have each Jaguar assigned a unique ID number. Sometimes they forget who they are and revert back to the default, or mistakenly get programmed the same as another.

When programming them it is best to have only one at a time on the bus, like it says in the manual.

-Hugh

[linuxboy]

So I just reflashed two jags individually and reassigned the IDs to them and still no luck. Even if both are hooked up hitting assign does not make them both flash green, only the first one meaning that even broadcasting does not reach the second one in the chain. I'm out of ideas so I'm really hoping for some magic fix from you guys.

Oliver

[linuxboy]

WE GOT IT WORKING!!!!!

Okay now that I'm done with the excitement outburst I will let you all know how. Turns out the issue was the impedence (as many people said). The problem exactly was our 100ohm resistors were not enough for a terminator plug. Instead we are using 680ohm resistors on both ends of the bus. That worked for 2 Jags and we are seeing if it will work with more.

[linuxboy]

Actually it's not working quite as well as it seemed. It can't do more than two and it seems to fail on longer wires. . Oh well looks like PWM for this year and I'll try to figure out CAN on off season,

[kamocat]

You say the 680 ohm resistors worked as termination when the 100 ohm didn't?
I would double-check the cabling. Are they all straight-through?

[drakesword]

Originally Posted by linuxboy

So I just reflashed two jags individually and reassigned the IDs to them and still no luck. Even if both are hooked up hitting assign does not make them both flash green, only the first one meaning that even broadcasting does not reach the second one in the chain. I'm out of ideas so I'm really hoping for some magic fix from you guys.

Oliver

This sounds to me like you made a cross over cable instead of a strait through cable. The middle two wires must not be switched!