Vectrino "Data buffer overflow"

Dear Nortek,

I'm testing a couple new Vectrinoes, and keep getting the error "Data Buffer overflow" in a red bar across the bottom of the Vectrino Plus software.  This error appears to correspond to missing data points.

I've tried several serial ports (both native and USB converters) of several computers with the same result.  It appears to be independent of other processes running on the computer.

I've also tried sampling speeds between 100Hz and 200Hz with the same result.

The data dropping does not always appear immediately, but after anywhere between 1 second and a few minutes.  In one case, there was no dropped data for ~3.5 hours and then suddenly lots of dropped data for the next ~10 hours.

Here are typical drop patterns:
-Computer one: 5-40 (as many as 300) missing data points every ~300-1000 samples at 200 Hz.
- Computer two: 65-95 missing data points every ~300 samples at 200 Hz

What can cause this error, and how do I get it to stop dropping data?

I am using the standard Nortek supplied 10m RS-232 communication cable, and Windows XP 32 or Windows 7 x64.


A second question:

What does "checksum error" mean?  I get this instead of "Data buffer overflow" when sampling the vectrino through a remote serial server.  Otherwise, the behaviour (onset, frequency, missing data) is the same as the data buffer error described above.


I'd like to sort this out as soon as possible, and so welcome any insight you can provide.

Thanks,

Peter

Hello Peter,

Here is a troubleshooting checklist that can be useful when encountering "data buffer overflow" errors or observing missing data points:

• Ensure no other applications are running
• Ensure there are no scheduled services (e.g. virus scan)
• Turn off power management
• Ensure the most recent serial device driver compatible with your Windows version is installed
• Check your serial device driver (advanced) settings - look for settings that may affect the performance (e.g. latencies)
• Check for noise sources aoround the cable run. The maximum distance will depend on the transmission speed (baud rate) and noise level.

A checksum error means there was a problem with the serial communications. The checksum is at it's simplest is the sum of all of the bytes from the the start of a data string to the end. This is generally encoded at the end of the data string and used to check for communication errors. A checksum error occurs when the computed checksum on the receiving end doesn't match the transmitted value. Generally, this means there's some noise on the communications line and one of the bits was mis-transmitted or something similar, although in this case it could be due to the data buffer overflow and the data strings getting a little out of sync. For example, a data string could start and then the buffer overflow error occurs, so a portion of that data string is lost. The Vectrino software picks up the stream from the buffer but is missing a little bit so the checksums don't match.

Best regards,
Oistein

Hi Oistein,

I have not yet resolved the data buffer issue, but the plot thickens. 

I have tried all of your suggestions.  It seems that this problem only occurs on some computers.  Others work perfectly fine.

In windows XP 32, I've tried it on 5 computers; 2 Xeon and 3 Core2 architecture computers. 

It seems the Nortek software works without dropped data on the Core2 computers, but not the Xeons.  I tested built in serial ports, usb-serial converters (supplied by Nortek), and serial device servers on each computer with the same result.  Very strange.

Any idea what might cause this?  Have you tested the Vectrino Plus software on computers with Xeon architecture?  Anything else I can try?

Thanks,

Peter

Hi Peter,

Did you monitor CPU performance in Windows Task Manager to see if there was a difference between the Core 2 and Xeons? What type of computers are they (name, model etc.)?

Best regards,
Oistein

Hi Oistein,

No difference in task manager between processor types.  Also no difference before and after dropouts begin.

The computers are:

Working:

- Dell Optiplex 755
core2 quad Q6600 2.4 Ghz
Windows XP 32 bit.  (this computer has the same buffer overflow problem when running windows 7 x64...)

- Macbook Pro Laptop
core2duo 2.16 Ghz, Win XP 32

- Supermicro 4U server
Intel Core2Quad Q6600 2.4 GHz, Asus motherboard


Not Working:

- Supermicro 1U server
Intel Xeon X3430 quad core 2.40 GHz, Supermicro motherboard

- Supermicro 4U server with high speed RAID array
Intel Xeon E5335 2.00 GHz, supermicro motherboard


Have you ever tested the software on Xeon processors?

Peter

Hi Peter,

I have googled 'xeon' and 'buffer overrun' and come across a few forum postings indicating a possible link to the Xeon 'hyperthreading' feature. Did you try disabling hyperthreading? I believe it is a BIOS setting.

Best regards,
Oistein

Hi Oistein,

Indeed, I have already disabled 'hyperthreading', alas without success.

However, I do have a solution.  At the suggestion of Peter Rusello at Nortek USA, I tried version 1.08 of the Vectrino Plus software.  It appears to be working (without dropping data) after >12 hours of sampling.

I'm not sure what changed between version 1.08 and 1.15 that would cause that, but if you figure it out, I would be curious to know.

Best,
Peter