Agilent Oscilloscope 54622D Logic Analyzer Cable

[y2khris]

Hi guys,

I've been watching Dave's youtube channel for a long time now and per his review of the 54622D, I've gone and picked one up.  I am quite a beginner to the electronics world but I am very interested in learning as much as I can and can use a nudge in the right direction.  The oscilloscope works great but I purchased it to be able to use it as a logic analyzer as well because I already have the Rigol DS1102E as a normal oscilloscope.  After playing with the scope and using it a little bit, I discovered the logic analyzer portion had a ribbon cable port, much like the ones from our old IDE drives, and looked at the internet for leads and then I saw the $300 price tag and my heart stopped.

I have some Arduino projects going on and I'd like to see what is going on with the I2C bus.  I went and bought some male-female jumpers and hooked them up to the logic analyzer and to test it, I hooked it into my Arduino's I2C, in line with some of my sensors and the sensors stopped outputting info.  I put a 100 ohm resistor between the two and I still had the same issue.  I then turned on my Agilent 33120A on a 1KHz square wave and while it does read the square wave, it seems to be made out of hundreds of other, differently sized square waves inside of it.  What can I do to make it look like a solid square wave?  Is there a nominal voltage that I should be running?

I've seen these eBay auction: #http://www.ebay.com/itm/HP-Agilent-Logic-Analyzer-Cable-16510-61602/161855954291?_trksid=p2047675.c100005.m1851&_trkparms=aid%3D222007%26algo%3DSIC.MBE%26ao%3D1%26asc%3D36016%26meid%3D5245fb8b1a2f4426b01a0258c517a04b%26pid%3D100005%26rk%3D2%26rkt%3D6%26sd%3D221268342023 and have been thinking of hacking it up but I don't know if it is the right approach.  I would like to make this work and create descent logic analyzer test setup for the 54622D, but I don't have the experience to know where to go from here.  I don't mind the work as long as I can make this work correctly and have a good setup that will last me a while. 

[Howardlong]

I don't think that's the right cable, I couldn't get your link to work, but based on the part number in he URL it's designed to interface with a board connector.

54622D, super scope. Very good for beginners and more, super simple to use, super responsive UI. Boots in five seconds. I still have one, I can see why Dave raved over it. While it lacks serial decode, it does do serial triggering. It's so good, I bought a 54642D too which is basically the same scope but more bandwidth, and used both together for quite some time.

When I get back to the lab all being well in a couple of hours I'll get the part number(s) for the LA probe: there are more than one. While you may be able to jury rig something with an IDE cable, there is some jiggery pokery in the cable itself including lossy/resistive coax to improve bandwidth very significantly, maybe two orders of magnitude compared to simple flyng leads, not to mention getting the voltage levels right.

[y2khris]

Thanks for the reply.  One thing I don't quite have that would be great would be the pinout of the logic analyzer port.  If I had the pinout, at least I could begin to figure it out.  Do you by chance know which pin controls the clock and/or if the entire upper row is ground? 

[Howardlong]

There is an Agilent pdf somewhere with it on together with a bunch of other logic probes. Apologies, my Friday night imbibement appears to have extended somewhat, so it might be tomorrow unless a less lubricated forum participant can facilitate in the meantime.

[Someone]

There is an older document "Probing Solutions for Logic Analyzers" which has the pinout and termination requirements for the 40 pin probes.

[Howardlong]

The part numbers to look for are:
54620-61601
54620-68701
54620-61801
N2756-60001

As far as I can tell, they all relate to the same functioning device, although the last one is a re-model that's shipped with new model MSOs like the 3000T.

Make sure you get all the probe and ground flying leads and grabber clips: on one I purchased on ebay the seller did not disclose that one of the flying leads was missing.

The probes provide a 10:1 impedance jump, 100k at the probe and about 10k at the scope, so without the probe the inputs are 10x as sensitive. Maximum voltage a probe tips is +/-40V, or +/-4V at the scope inputs, but if you do jury rig something I would use a series 91k resistor in each probe lead rather than go direct to the IDE connector.

[y2khris]

Thank you all for your insight.  I will be looking over everything you guys have said and let you know how it goes! 

[Someone]

but if you do jury rig something I would use a series 91k resistor in each probe lead rather than go direct to the IDE connector.

Its not a rigged solution, the actual design for direct attachment is detailed in the document "Probing Solutions for Logic Analyzers".

[y2khris]

Thank you so much.  This is all pure gold!  I will be collecting all the parts I need this week.  Hopefully it turns into something useful.

[Howardlong]

but if you do jury rig something I would use a series 91k resistor in each probe lead rather than go direct to the IDE connector.

Its not a rigged solution, the actual design for direct attachment is detailed in the document "Probing Solutions for Logic Analyzers".

Some of that resistance is distributed within the leads in the real cable, that's why a simple lumped component soultion won't match the performance of the real cable.

[y2khris]

So I finally had a chance to start working on this project and I ended up picking up an IDS-40 connector, 26 gauge wire and a bunch of 91K resistors.  I soldered the wires directly to the connectors and I soldered the 91K resistors in line on the wires at staggered lengths so I don't have a "lumped component solution".   I then put heat shrink over the resistor and its solder joints and now I am waiting for my grabbers to arrive.  I also need to get a 40 pin cable to extend this one because the way that leads stick out of the side, I would have to force them into the logic analyzer and I'd rather just make it a little longer and keep my cable from getting broken solder joints.

I'll put up another update when it is all done.  Thank you all so much for all your help.

[chihaxinh]

Hi y2khris

I have problem like you, buy osc and seller missing LA cable !

Do you have finish diy LA cable and It's working well ?