Is this a USB port? (based on measurements) - Page 1
Forum section: electronics / projects

author: PP3331
author_rank: Contributor
timestamp: March 07, 2020, 08:35:06 pm
content: I have a four conductor connector on a device that is rumored to be a USB port. However, I don't know this for a fact, and do not want to connect it and blow it out. I was advised to use a multimeter in diode mode to check the various pins. Here are the results:On the port in diode mode:---- red meter lead (gnd?)---- 1.760v (data?)---- 1.760v (data?)---- 1.494v (+5?)Are there other combinations of readings I should make? Are these readings reasonable for a USB port? Obviously, I don't want to apply 5v to a 3v circuit or reverse polarity. Any thoughts? Thanks.

author: Gyro
author_rank: Super Contributor
timestamp: March 07, 2020, 08:49:47 pm
content: I don't understand why you have started a new thread on this, when you already have one running with the same information.https://www.eevblog.com/forum/projects/safely-applying-power-to-unlabeled-unknown-usb-pc-board-connector/

author: PP3331
author_rank: Contributor
timestamp: March 07, 2020, 08:57:52 pm
content: Because I now have the measurements and wanted to have the topic reflect that fact and the specific question which is different than on the OP. If you have thoughts on those measurements that would be much appreciated. Thanks.

author: Gyro
author_rank: Super Contributor
timestamp: March 07, 2020, 09:48:15 pm
content: But you put the same data in Reply #2 in the other thread!Frankly, you haven't given nearly enough information (in either thread). Nothing about what the "device" actually is. What's on the board (you clearly have access to a header). Photo's etc. There's no way I could tell one way or the other from the available information.If I were you, I would provide sufficient information (as above) in the other thread and request a Mod (use the Report to moderator link) to lock this thread.People (including Mods) tend to get ratty when they find themselves wasting time contributing to a thread, only to find that somebody else has posted the same advice on the other thread!P.S. Especially when you are now getting replies in the other thread.

author: PP3331
author_rank: Contributor
timestamp: March 07, 2020, 10:03:23 pm
content: I'll go back to the original thread for further discussion after this, but there isn't much to add. Photos are worthless (though I do have them) since it's a fairly rare and very tiny Molex. I have been "told" off the record that it's probably USB. I don't have access to the rest of the circuit (currently) because the owner doesn't want me disassembling unless absolutely necessary. So unless I just want to take a leap of faith and apply power (perhaps gradually) I don't have anything to really go on except the measurements I can takein situ.Thanks.

author: ogden
author_rank: Super Contributor
timestamp: March 07, 2020, 10:12:05 pm
content: Quote from: PP3331 on March 07, 2020, 10:03:23 pmOwner do not let you look at the device and analyze it properly, yet he is fine that you will apply voltage not even knowing - it is OK or not?

author: PP3331
author_rank: Contributor
timestamp: March 07, 2020, 10:14:49 pm
content: I asked the same thing. I think he doesn't want me damaging the case even if the circuit is blown out. Mixed up priorities, from my standpoint.

author: PP3331
author_rank: Contributor
timestamp: March 07, 2020, 10:48:34 pm
content: Ah, fed up fighting this. It's going to get opened up. Thanks all!

author: Simon
author_rank: Unknown
timestamp: March 08, 2020, 10:34:57 am
content: You can't run 2 threads on the same topic at the same time. It's insulting to members that are trying to help you unawares that the same parallel discussion is going on elsewhere. It's up to you if you want to piss everybody off or not.

author: PP3331
author_rank: Contributor
timestamp: March 08, 2020, 03:42:38 pm
content: Despite the social media moderation drama -- which I've seen in different contexts for decades so seeing it here isn't a surprise -- the advice actually offered on these threads for this issue was USEFUL and helped to solve the problem. The original measurement advice worked, and was verified by getting permission to crack the case to get at the PCB. And yes, it turns out to be a USB port, with "non-standard" pin ordering. And for that excellent technical advice I thank the readership, and as a long-time forum designer and moderator myself, I offer the free advice of trying to turn down the moderation emotional volume a bit whenever possible. Yes, big forums take a lot of work to manage, but we're all in this together, one way or another. Of course, as Allen Sherman sang, free advice is worth the price. In any case, my thanks.

author: ogden
author_rank: Super Contributor
timestamp: March 08, 2020, 03:55:29 pm
content: Quote from: PP3331 on March 08, 2020, 03:42:38 pmConsidering your forum experience, please end this thread with better endingthan just "thanks" - provide useful information for others. Sum-up your experience & findings, maybe show some picture soothers can learnas well, not only you.

author: Simon
author_rank: Unknown
timestamp: March 08, 2020, 04:19:17 pm
content: Quote from: PP3331 on March 08, 2020, 03:42:38 pmModeration happens on the basis of reports from members! the fact that moderation happened means you pissed off the existing users! if you wish to work with no disregard for existing users you may find you are giving yourself the finger in a mirror as no one else will want to talk to you!