Really Long Delay (28s) Getting Data Out with SNAP-SCM-CAN2b


#1

Hi All,

I am suffering a problem with a SNAP-SCM-CAN2b module we have installed. It receives data and has no errors (including status LEDs) and the data is well formed (i.e. not scrambled or garbled) the problem is that the data has a 28 second delay. I got this delay by comparing the data arrival time to the data coming through a separate CAN bus USB adapter.

I suspect I have misconfigured something, perhaps related to the buffering in the CAN bus reader but I can’t work out what that is. Maybe I am not reading it quickly enough so that its buffer is filling up?

Everything else about the PAC works fine. It is running several charts but they all appear to be working fine too.

I am communicating with the PAC over ethernet, however separate experiments have confirmed that the PAC to computer communications delay is under 40 milliseconds.

It’s a mystery to me because once I get the data it’s fine, it’s just that it takes a long time to get there.

Thanks in Advance
Bart


#2

Hi Bart,

Have you tried connecting to the module via telnet? (To narrow down where the delay is happening.) Might also be interesting to see if anything changes when you only run the chart that’s doing this (not those other charts you mentioned).

Also, don’t forget our [B][U]support[/U][/B] is FREE! and if you’re running into some bug or something missing from the manual(s), we’d like to get that corrected ASAP.

-Mary


#3

Hi Mary,

Sorry for my late reply. I did not do the telnet thing but we have determined that the delay is solely due to the CAN bus module itself. The PAC is able to ‘echo back’ data sent from the control computer with minimal excess delay (i.e. any delay is solely due to speeds of communication loops etc.). All the excess delay seems to be occurring either in the CAN bus module itself or the chart.

As said, no data is actually lost, just delayed by a very long time.

I think I will put in a support call.

Thanks,
Bart


#4

Yes! You should, they can help you get to the bottom if it. I hope you’ll report back on the resolution. Email is best: support@opto22.com