Unexplained intermittent CAN / 2CAN Jaguar problems at GSR

[heydowns]

Originally Posted by drakesword

To address potential blocking we will make individual threads to set output to each motor.

Just a warning - the bus transactions are serialized via a monitor lock in the CANJaguar driver (at least on the C++ version, as well as in the last public source code I can easily get to of the Java version). Thus threading the transactions won't entirely alleviate any potential for blocking with respect to one another (that is, if one Jag thread were to block waiting for a bus response all other concurrently executing Jag threads will also block). Of course, it can offer the advantage of allowing the remainder of your code to execute while the Jag thread(s) are tied up.

[drakesword]

Originally Posted by heydowns

Of course, it can offer the advantage of allowing the remainder of your code to execute while the Jag thread(s) are tied up.

Thats the effect I was after

@Phalanx

According to some other threads the ground wire between jags can cause ground loop interference eg. the ground of one jag may be higher then the ground of another jag

[techhelpbb]

Just to clear up my post above...

Even with our Jaguars using %VBUS with CAN and only the potentiometers connected to the Jaguars as sensors...

We still get time out errors in addition to the occasional lock up.

The more wear and tear we put on our batteries the worse the problem gets.

Using the PID loops in the Jaguars seems to make the problems worse for us (to the point of dysfunction in some cases).

Due to the competition schedule, and now our additional appearance in St. Louis, we'll probably not want to tinker too much with the practice or production robot until it can't impact on performance at competition.

As soon as we can, I'd like to revisit this issue...even if we have to slap together another frame.
Our team has a spare new cRIO and I have a new Jaguar and some CIM motors.

[kamocat]

I wonder if we could be seeing the effects of process starving on the Jaguar?

CAN and RS232 communications are low priority tasks in the processor.

[taichichuan]

Originally Posted by kamocat

I wonder if we could be seeing the effects of process starving on the Jaguar?

CAN and RS232 communications are low priority tasks in the processor.

That might explain the serial CAN problems, but we saw them with the 2CAN via Ethernet as well. I think serial CAN tops out at something like 2K pps but the 2CAN jumps that to more like 8K pps from what I understand. At least it's comforting to know that it's not just a 2CAN problem.

Mike

[JasonStern]

1) Correct/Proper wiring both CAN and Power.
We verified all wiring. In addition, the termination resistor was soldered onto short wires and not crimped directly to the plug.

2) Ground isolation of components.
All components were mounted to Plexiglas and the frame was verified as electrically isolated by the DC inspection team.

3) CAN Interface used, Serial or 2CAN
2CAN*

4) Type of JAGS used, Black, Grey, Both
Both

5) The programming language used
Java

6) The control mode(s) used.
Speed, %VBUS

7) encoders, pots, limit switches are being used.
US Digital E3 quadrature encoders with 1024 CPR and 1/2" bore for the black jaguars; nothing for the grey.

*We can cause the jaguars to freeze in both %VBUS and Speed mode using the BD-COMM utility and quickly changing values. This is true even if we remove all other jaguars from the bus.

-Jason

[nuttle]

Not to pile on, but in case this may help either another team or anyone working on these problems:


- If you try to use an indexed encoder with the closed-loop PID control feature of the Jags, I'm pretty sure this won't work (based on our experiences). The issue here is probably that the index mark causes the encoder count to be reset once per revolution, and the PID logic doesn't expect this behavior, since it is not a continuous count but a count that essentially wraps around at a certain point. You can get around this by disconnecting the index pin -- certainly worth a try if this applies to you. You'll have to rely on the encoder being at zero when things start up, or doing something else to reference the count.


- If you are using PID, stuttering could certainly be caused by not having the P/I/D coefficients set correctly.

- I second the recommendation not to crimp an RJ connector directly to the solid leads coming from a resistor; this is not as reliable as making a short pigtail using cable that is designed for use with these connectors and soldering the terminator resistor to this.
- If you use a 2CAN, the 2CAN webpage is helpful for seeing how things are behaving. In particular, it provides error counters that can help validate wiring and basic communications connectivity.

[John Heden]

Greetings All,

We started this thread after experiencing a number of catastrophic CAN startup problems at the GSR regional and while we were hopeful that the V29 update would provide some relief on this issue, we continued to see this problem occasionally at the Hartford regional this past weekend. While our Drive team was instructed to monitor the Driver Station diagnostic tab for streaming CAN errors, they became complacent on Friday after never encountering the issue on Thursday. A Driverstation side CRIO Reboot did NOT recover the situation after the match began and we sat idle during the entire match (our Alliance won without our participation).

We experienced this problem again on Saturday while setting up before opening ceremonies (we had the first match) and again the system did NOT recover with a warm Driver station reboot on the first attempt and required either a third reboot attempt or possibly an actual robot power cycle to recover. This early morning triple failure scared us a bit but we NEVER experienced this catastrophic CAN failure during our later matches. The drive team did occasionally see a few startup CAN errors that concerned (panicked) them but did not see the catastrophic scrolling CAN error behavior.

We saw this failure occur during GSR at frequency of about 1 out of 6 matches ONLY while we were actually on the playing field and never while tethered to the robot with approximately the same statistic at Hartford. There was an observation that was seen once on the practice field making us curious as to whether the use of the radio was some how a catalyzing factor. Our radio was physically touching the 2CAN so we decided to try to give them some space (inverse square law). We couldn't try this with the radio in the pits but we proceeded to do some repetitive tethered power on/off tests trying out different power up sequences (relative to laptop) to try to reproduce this. We must have done this 20 or 30 times and NEVER saw a single CAN transaction failure and certainly not the continuous scrolling catastrophic CAN failure signature. We thought this was a radio ONLY failure but we did eventually experience this once while we were tethered in the pits. A quick power cycle and the problem went away! I wish we had tried a soft reboot as an experiment but our robot was being queued and our goal at that point was recovery rather than experimentation.

I believe we have some type of CAN/2CAN/CRIO/WPILib startup race condition that occasionally prevents some type of low level initialization causing the complete loss of the CAN bus. The manifestation we see is as if we simply pulled the CAN cable out of the 2CAN preventing any successful transaction to any CAN device. I believe use of the radio somehow amplifies this window of opportunity for failure given our ratio of match failures to pit failures and given we power up much more often while tethered in the pits than during actual matches. We had little working radio based experience prior to arriving at GSR due to the late availability of the physical robot for software testing. This radio testing and its influence on CAN failures will be a priority when we get our robot back. My apologies that some of this data is so soft but we were unable to find any hard correlation or anything definitive other than an occasional complete startup failure that always recovers on a power cycle mostly ruling out cabling issues. This failure occurs BEFORE being enabled essentially ruling out any real voltage drop or current/noise problems. If we startup successfully, we do run successfully. In fact, we have performed number of tests where we pull the breakers out of the Jags and even the 2CAN. This causes CAN errors to be reported but the system nicely recovers within a couple of seconds after we plug the breakers back in. We use the default voltage mode so others who have a more complex initialization or control scheme may not recover so easily.

There was also some anecdotal data coming from others at Hartford (other teams and even some of the Harford technical field folks) that believe the serial CAN interface is more robust than the 2CAN and recommended we switch away from the 2CAN. While this startup problem is catastrophic, it feels like some type of simple initialization glitch that is solvable. The CAN & 2CAN approach is a nice technology with perhaps this single gremlin to be exorcised. We'll try to diagnose this further when our bot comes home but unless we can convince our team that this is behind us, we may be forced to return to the simpler ways of PWMs....

Cheers and thanks,

John

1) CAN Wiring is correct with proper termination.
2) All components are ground isolated from the frame and electrical wiring has no shorts or ground faults.
3) We run the CRIO connection directly to the radio and connect the radio directly to the 2CAN rather than passing all CRIO traffic through the 2CAN.
4) We used all Tan JAGS.
5) We Programmed with C++.
6) Used Voltage Mode only.
7) 3 Jags with optical encoders, 1 of these has a single limit switch as well
2 Jags each with 2 limit switches, no encoder

8) I should also add that our software launches a separate dashboard thread at the end of the constructor AFTER the Jags and other robot objects are created with this data (encoder values, currents, voltages, etc) being read for display and capture by our custom dashboard. This explains why we see a continuous never ending data stream while others, I suspect, may see a number of errors during startup that stop but resume once they are enabled and autonomous & control Jaguar transactions begin.

[Hugh Meyer]

John,

I may be misunderstanding your comment # 3. Please clarify if my comments don't make sense.

*****
3) We run the CRIO connection directly to the radio and connect the radio directly to the 2CAN rather than passing all CRIO traffic through the 2CAN.
*****

I thought the 2CAN was to be connected to the CRIO on port # 2. Since port # 2 is on a different network the traffic is isolated from the robot communication traffic on the wireless. That is how ours is wired and we just completed 2 regional events without any control issues. We had other issues, just not control ones...

It seems adding that additional load through the radio switch and robot communication network could indeed cause problems.

-Hugh

[taichichuan]

Originally Posted by Hugh Meyer

John,

I may be misunderstanding your comment # 3. Please clarify if my comments don't make sense.

*****
3) We run the CRIO connection directly to the radio and connect the radio directly to the 2CAN rather than passing all CRIO traffic through the 2CAN.
*****

I thought the 2CAN was to be connected to the CRIO on port # 2. Since port # 2 is on a different network the traffic is isolated from the robot communication traffic on the wireless. That is how ours is wired and we just completed 2 regional events without any control issues. We had other issues, just not control ones...

It seems adding that additional load through the radio switch and robot communication network could indeed cause problems.

-Hugh

Routing CAN traffic through the radio could certainly cause problems. The radio's ports have a limited amount of buffer space before the 802.3x congestion control messages start flying around on the net. I'm not sure what the 2CAN would do if it suddenly started getting a lot of source quench message traffic. Certainly, packets would start getting lost and that would be bad on a half-duplex style network like CAN (at least in the way it's implemented for FIRST). So, it's probably better to wire the 2CAN to port 1 on the cRIO and wire the radio on the other port of the 2CAN.

My $.02,

Mike

[John Heden]

Originally Posted by taichichuan

Routing CAN traffic through the radio could certainly cause problems. The radio's ports have a limited amount of buffer space before the 802.3x congestion control messages start flying around on the net. I'm not sure what the 2CAN would do if it suddenly started getting a lot of source quench message traffic. Certainly, packets would start getting lost and that would be bad on a half-duplex style network like CAN (at least in the way it's implemented for FIRST). So, it's probably better to wire the 2CAN to port 1 on the cRIO and wire the radio on the other port of the 2CAN.

My $.02,

Mike

Mike,

Thanks for your thoughts. We initially had the 2CAN device on the CRIO port 1 connector which is where we first started to see our problems. The buffer capacity of the 2CAN vs. the radio was unclear but our intuition gave the radio the advantage here. I believe our next step will be to simply move to port 2 of the CRIO and see whether that helps things.

Thanks,

John

[nuttle]

Do you know if your 2CAN has had the firmware updated to version 2.5 or not? We have a regional this coming week/end and will try out v29 on the cRIO. We've been using serial, but it is easy enough to switch back and forth that we might try the 2CAN again, at least for practice matches. We have not yet had a chance to try either of these updates.

[jtdowney]

Originally Posted by taichichuan

Routing CAN traffic through the radio could certainly cause problems. The radio's ports have a limited amount of buffer space before the 802.3x congestion control messages start flying around on the net. I'm not sure what the 2CAN would do if it suddenly started getting a lot of source quench message traffic. Certainly, packets would start getting lost and that would be bad on a half-duplex style network like CAN (at least in the way it's implemented for FIRST). So, it's probably better to wire the 2CAN to port 1 on the cRIO and wire the radio on the other port of the 2CAN.

My $.02,

Mike

R50A states "The DAP-1522 radio is connected to the cRIO-FRC Ethernet port 1 (either directly or via a CAT5 Ethernet pigtail)." We took this to mean that under no circumstance can an active device (2CAN) sit between the DAP-1522 and the cRIO. That leaves two choices, connect the 2CAN to the DAP-1522 or connect the 2CAN to Ethernet port 2 on the cRIO.

My teams robot (programmed with Java using IterativeRobot) has gone through one event with our 2CAN plugged into our DAP-1522 and have had no CAN related trouble. We were running cRIO v28 (v29 wasn't out at the time) and 2CAN firmware v2.5 with the SVN rev 66 plugin on the cRIO. We have 6 black jaguars on the CAN bus with no sensor inputs or limit switches.

Perhaps we were very fortunate during our regional but we have not had any serious CAN issues (knock on wood) since build. All of our trouble then could be traced back to poorly made cables when we did have problems.

I am hoping our luck caries us through championship.

[mjcoss]

We continue to be plagued with timeouts on the CAN bus. And yes, I've checked the termination, and it all looks good. We are running V29 and I don't have the numbers for the plugin or the 2CAN firmware.

One thing that I have seen which is causing no end of issues is that if you get a timeout on the messages, the API is return no indication of the failure. So, for example, if the GetForwardLimitOK() function is called, and times out, you get back false. There is no way to know that that has happened and if you are making decisions based on these results... We have an encoder on our lift mechanism. To zero the encoder, we drive to the bottom limit switch, and when we get there, we set the encoder to 0. This works fine until we lose the message due to timeout. From that point on the lift is offset by where ever the timeout occurred. There really needs to be a way within the API to detect that the transaction timed out.

Of course, the best answer would be that we don't have any timeouts.

Another observation related to timeouts is that we have an on board compressor and if during initial startup the pressure sensor indicates that the compressor should run and starts the compressor immediately, we get a number of timeout messages.

All in all, I'm really regretting the decision to use the CAN bus. And for the most part all of the features that I really wanted to use, that were provided by the CAN bus, proved to be unusable.

[John Heden]

Originally Posted by jtdowney

R50A states "The DAP-1522 radio is connected to the cRIO-FRC Ethernet port 1 (either directly or via a CAT5 Ethernet pigtail)." We took this to mean that under no circumstance can an active device (2CAN) sit between the DAP-1522 and the cRIO. That leaves two choices, connect the 2CAN to the DAP-1522 or connect the 2CAN to Ethernet port 2 on the cRIO.

My teams robot (programmed with Java using IterativeRobot) has gone through one event with our 2CAN plugged into our DAP-1522 and have had no CAN related trouble. We were running cRIO v28 (v29 wasn't out at the time) and 2CAN firmware v2.5 with the SVN rev 66 plugin on the cRIO. We have 6 black jaguars on the CAN bus with no sensor inputs or limit switches.

Perhaps we were very fortunate during our regional but we have not had any serious CAN issues (knock on wood) since build. All of our trouble then could be traced back to poorly made cables when we did have problems.

I am hoping our luck caries us through championship.

Greetings,

R59 adds some expansion to R50 stating:
<R59> If CAN-bus communications are used, the CAN-bus must be connected to the cRIO-FRC through either the Ethernet network connected to Port 1, Port 2, or the DB-9 RS-232 port connection.

Our 2CAN connection directly to the radio is probably a rule violation (inadvertent) but was an attempt to prevent errors when we were connected (legally) to port 1. A port 2 to 2CAN connection will be our next experiment to try to avoid this issue.

john