Products > Test Equipment
Brymen IR connection protocol - Anyone sniffed it yet?
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onmobile:
Hello,

Has anyone sniffed the brymen 867 or 869 IR connection? It would be good to know what's going on in there, how the handshake looks like, how data gets transmitted, baudrate, etc.

I guess a simple sniffing session for one data acquisition from the DMM, would be enough to get the rest of us started in making our own connection cables.
Slothie:
I recently bought a Brymen 257 Multimeter and that has an IR port. I read on here somewhere that the software for the IR cable has PDF's with it that detail the protocol for all models. This software is downloadable from Brymen's website as a windows installer. I have downloaded it but not yet used it because I dont have a working windows PC (all Linux...) at the moment but I'm going to set up a VM and see if I can extract the files.
Somewhere on the forum (sorry I looked for it but couldnt find it again) someone posted the PDF for the '867 and I recall it looked like the port just outputs a bitstream that indicates if the segments of the display are on or off.
jadew:
Indeed, they do publish the protocol, but it's the protocol between the PC and the cable, which then makes the request to the DMM trough IR.

What they're not saying in there is how they are forwarding the data: How is the IR signal modulated? What baudrate? And what is the cable sending before the user bytes - I suspect it might send out some unknown bytes, for framing and for keeping the protocol closed.

If someone who already owns a cable, could capture the IR stream, from the cable to the device, I would greatly appreciate it. (oscilloscope capture or logic analyzer, anything would do)

Currently I'm trying to initialize it based on the mentioned PDFs, however lots of variables are a mystery.

I got the protocol docs from the brymen software zip, located at: http://brymen.com/product-html/software-download/BM860-Bs86x-V6002s-use-BC86X-Win7.zip

BU-86x being the cable for the BM867 and BM869.

I also found this:
http://g-tech.no-ip.org/~mrnuke/brymen_protocols/500000-count%20DMMs%20protocol-r1.pdf

Which seems to be similar to http://sigrok.org/wiki/Device_cables#Brymen_BC-85Xa which was used by Extech. From the last PDF I linked, it looks like brymen changed something to the cable/protocol between BR85X and BC-85Xa - what exactly was that, I don't know, but it could be anything from the IR baudrate to just a few frame bytes or something silly. The change might have been propagated to BU-86x too, but again, just a guess.

What's clear is that they like to change stuff, apparently just to make them incompatible, in order to get you to spend another $60 on a cable which can be made with $4 parts.

What I did notice by checking their PDFs for other products is that they usually use a 9600 baudrate for the serial connection, which makes me think they might use the same baudrate for the IR communication - just a guess tho.

Anyway, if someone is willing to capture some traffic from the cable, I'd appreciate it and I promise to share whatever results I get.
madshaman:
I've got a BM867 with the BU-86x kit.  I can't guarantee I'll ever get around to it, but if I find any extra time I could give it a go.
jadew:

--- Quote from: madshaman on March 28, 2013, 07:08:39 am ---I've got a BM867 with the BU-86x kit.  I can't guarantee I'll ever get around to it, but if I find any extra time I could give it a go.

--- End quote ---

That would nice. I managed to get some sort of response from the meter last night, but it wasn't what I was hoping for so I started blasting it with consecutive numbers + the specified 4 bytes (00 00 86 66), however I stopped, because I realized that if I keep sending Junk I might overwrite calibration data or something. Hopefully I did not do that, I guess I'll know for sure once I take a look at how real data looks like.

Thanks for offering.
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