Constant LJME_TRANSACTION_ID_ERR in Python. Latest LJ Firmware, Latest LJM, Debian 9 | LabJack
 

Constant LJME_TRANSACTION_ID_ERR in Python. Latest LJ Firmware, Latest LJM, Debian 9

5 posts / 0 new
Last post
JPA
jefferyanderson's picture
Constant LJME_TRANSACTION_ID_ERR in Python. Latest LJ Firmware, Latest LJM, Debian 9

Having issues with LJME_TRANSACTION_ID_ERR

I'm running the latest release code for both the LJM library on a Debian 9 machine (from labjack_ljm_software_2018_05_15_x86_64_0.tar.gz), as well as the latest firmware in the LabJack (v1.0255)
I've observed this now with two LabJack T7s, and the issue shows up with both Ethernet and USB.
I switched to USB thinking maybe there were some networking issues at play, e.g. perhaps the switch was periodically dropping packets or similar, but in fact USB makes the problem far worse.

With USB my stream logging code will only run around 130s (it's quite consistent) before throwing LJME_TRANSACTION_ID_ERR, while with Ethernet it runs longer but is far less deterministic in its failure. There's a direct relationship w/ how fast I scan the inputs and how fast this error shows up (See below).

Since I started with one of the provided Python examples, I'll show some of the parameter names and output in case this helps illustrate things a bit better:

scanRate = 2 #kHz

scanRate *= 1000

scansPerRead = int(scanRate/4)

stream_buffer_size_bytes = 8192

I never see anything in 'skipped scans':

  • Total scans = 375000
  • Time taken = 187.519298 seconds
  • LJM Scan Rate = 2000.000000 scans/second
  • Timed Scan Rate = 1999.794176 scans/second
  • Timed Sample Rate = 11998.765055 samples/second
  • Skipped scans = 0

I've tried increasing the buffer to the maximum of the T7, and the issue still shows up (in fact I started there, but then started revising down looking for a change in behavior). I'm scanning the following:

aScanListNames = ["CORE_TIMER","STREAM_DATA_CAPTURE_16","SYSTEM_TIMER_20HZ","STREAM_DATA_CAPTURE_16","AIN0", "AIN1"]

 

From the base configuration shown above:

  • Faster scanning (4kHz) impact: Fails at 65s (direct relationship)
  • Faster scanning (8kHz) impact: Fails at 32s (direct relationship)
  • scansPerRead (/8) impact: No impact
  • scansPerRead (/2) impact: No impact
  • scansPerRead (/100) impact: No impact
  • stream_buffer_size_bytes (the max of 32768) impact: No impact
  • stream_buffer_size_bytes (the max of 4096) impact: No impact
LabJack Support
LabJack Support's picture
Please try upgrading to the

Please try upgrading to the most recent beta LJM version.

JPA
jefferyanderson's picture
Working on it now, thanks.

Working on it now, thanks. What is the correct uninstall procedure for LJM on Linux?

LabJack Support
LabJack Support's picture
You  don't need to uninstall

You  don't need to uninstall to install another version, since all relevant files will be overwritten by any particular version of the installer, but to uninstall:

rm -f /usr/local/lib/libLabJackM*
rm -f /usr/local/include/LabJackM.h
rm -rf /usr/local/share/LabJack
JPA
jefferyanderson's picture
I can confirm that installing

I can confirm that installing the latest beta version totally resolved the issue. Thank you.