USB using nonstandard connectors  - Page 1
Forum section: electronics / projects

author: rakeshm55
author_rank: Regular Contributor
timestamp: November 09, 2018, 12:25:56 pm
content: I want to have a non standard connector on chassis to handle USB. From my board USB signals will be routed to front panel PCB with chassis circular data connector.How to do the wiring for it??I am looking for a High Speed USB2.0 standard.I guess I need to consider following signalsVBUSGNDD+D-What to do with the braid shield of usb cable.?? Should I route it to main PCBWhat for a HS USB 2.0 480mbps what kind connectors i need to consider to avoid impedance mismatch.

author: Gyro
author_rank: Super Contributor
timestamp: November 09, 2018, 01:26:07 pm
content: If you look closely at a standard USB connector you will see that the VBUS and GND contacts are longer - they are designed to make contact before the D+ and D-. This is for ESD and proper signalling purposes. Whatever connector you use would have to mimic this action.Normally you would want a pretty good reason for deviating from standard USB connectors.

author: T3sl4co1l
author_rank: Super Contributor
timestamp: November 09, 2018, 01:51:25 pm
content: Noteworthy experience:Had a customer who wanted to use USB to communicate to peripherals (using a noncompliant supply voltage), in an automotive environment.They insisted on plastic circular connectors and unshielded cables (actually the cables were shielded, but that means nothing if it's not maintained throughout the connector and harness). Mostly for cost.We pushed back, suggesting they use a more traditional RS-485 interface, or the like. They insisted.Come testing day, and their peripherals are dropping like flies when hit with radiated and fast-transient (EFT) interference.Possibly, they could've at least addressed it in software (they were running a Linux SoM), but it seems their devs never got around to it, or perhaps weren't experienced enough with Linux, or were in general too heavily loaded with other activities to address it.We had to put the guts inside shielded enclosures, with metallic connectors tied to the cable shields. That got it to pass several kV of EFT, more than good enough. (It didn't need to be quite as robust as it ended up, but there was no just-good-enough option available that was cheaper.)The customer needed a $50 module, which would've been fine otherwise. But we ended up delivering a $200 module.That IP66 rated EMC box sure is sexy. It doesn't even make sense when you look at it -- the gasket feels sandy, how can it seal? But lo and behold, it does indeed seal against dust and water, and it does indeed conduct very nicely (a couple of ohms between any pairs of points inside the enclosure). But that price...Tim

author: Gribo
author_rank: Frequent Contributor
timestamp: November 09, 2018, 01:53:40 pm
content: There are chassis mounted round USB shells, from the usual suspects (TE, Amphenol, Samtec and others). If you also require miniature size, you are practically on your own.Example:https://www.alibaba.com/product-detail/Cnlinko-IP67-usb-type-a-usb_60290321922.html] https://www.alibaba.com/product-detail/Cnlinko-IP67-usb-type-a-usb_60290321922.html

author: T3sl4co1l
author_rank: Super Contributor
timestamp: November 09, 2018, 01:56:46 pm
content: Quote from: Gyro on November 09, 2018, 01:26:07 pmThis. They make IP-rated USB connectors -- pricey, basically a rubber boot molded over two ends. Awkward as hell. But you don't have to do any of the hard work we did and bang your head against impossible requirements. It just works.To actually answer the question: the shield goes to PCB ground, and GND is always* shield, so that's fine (or you can make it a pass-through, it's just a connector board, right?). The ESD note is a good one, and adding ESD diodes on the connector board might be worthwhile (else, at the USB interface chips). USB High Speed should be alright in a reasonable quality shielded twisted-pair cable. Don't worry about mismatch in the connectors, they aren't long enough to matter. You still have to obey maximum cable length restrictions.*I haven't seen any exception to this. I haven't read the USB standard in enough detail to know if they made note of any cases where you might want isolation between them.Tim

author: ConKbot
author_rank: Super Contributor
timestamp: November 09, 2018, 02:34:52 pm
content: Depends on the application. Inside a PC, front panel USB2.0 is connected to a motherboard with 0.1" pitch pin headers (separate pin for grounds and shield) 10-20mm of wire that's not impedance controlled as it makes its way from the cabled bundle to the pin header. Not a high-end or really impedance matched connector in the least. But the connector at the front of the case should be connected to the chassis, improving the shielding. But as Tim mentioned, it can turn into a right proper mess once you get outside of the case if you neglect shielding.

author: JVR
author_rank: Regular Contributor
timestamp: November 09, 2018, 03:10:47 pm
content: General rule of thumb: If you want to put USB through any connector cheaper than a USB connector, be prepared to pay for your sins. We build products with USB and Ethernet through LEMO connectors, with no issues, apart from price.USB is a commodity connector, do some search and you will find one that fits the purpose.

author: Ice-Tea
author_rank: Super Contributor
timestamp: November 09, 2018, 03:11:29 pm
content: Begs the questions: why?Also, instead of reinventing the wheel: what about stuff like this:https://www.mouser.be/ProductDetail/Phoenix-Contact/1440711?qs=%2fha2pyFadujuqEyjK0QjYJD6hvVPoPjT4aT0URM7FYk%3d

author: SiliconWizard
author_rank: Super Contributor
timestamp: November 09, 2018, 03:27:52 pm
content: There are proper USB chassis connectors.

author: rakeshm55
author_rank: Regular Contributor
timestamp: November 10, 2018, 10:59:37 am
content: Rather than price paucity of space at front panel was the reason to go for a single data connector....i have seen some radios using circular connectors at the front panel...eghttps://www.harris.com/solution/harris-falcon-iii-an-prc-117gv1c-multiband-networking-manpack-radioUse a circular connector for USB i not sure they are standard USB connectors...

author: bob225
author_rank: Frequent Contributor
timestamp: November 10, 2018, 11:57:30 am
content: Only thing that springs to mind is automotive usb connectors like the Molex HSautolink seriesorhttps://www.molex.com/molex/products/datasheet.jsp?part=active/0847290009_IO_CONNECTORS.xml(standard usb)

author: ratio
author_rank: Regular Contributor
timestamp: November 10, 2018, 12:24:20 pm
content: I've got several devices that use a plain old 1/8" headphone connector for USB service.Wish I could find a cable, I really want to dump the log from one of them...

author: Richard Crowley
author_rank: Super Contributor
timestamp: November 10, 2018, 12:38:37 pm
content: Quote from: rakeshm55 on November 09, 2018, 12:25:56 pmExtremely confusing.Is this "chassis circular data connector" INTERNAL to your gadget, or the EXTERNAL user-accessible connector?What is the connection from the board to the internal cable?What is the connection from the internal cable to the front panel?What is the connection external on the front panel to the user?How long is your internal cable path?Why isn't grounding/shielding already part of the external user connector?QuoteIf you look inside any of 10s of millions of computers, you will see that the USB cabling is implemented with bog-standard 0.1 inch header connectors and random wiring. They can get away with this largely because of the short distances involved. But shielding and grounding the external connector is critical.

author: NiHaoMike
author_rank: Super Contributor
timestamp: November 10, 2018, 03:30:02 pm
content: Quote from: Gyro on November 09, 2018, 01:26:07 pmA "good reason" is to bundle some non-USB signals into the same connector. But that can also be done with additional connectors spaced a defined distance from a standard USB connector and then making a custom plug with the matching connectors at the same spacing.

author: 001
author_rank: Super Contributor
timestamp: November 10, 2018, 03:38:53 pm
content: HuhWhy USB connectors so ugly and useless?Why nobody use simple 3.5 4-wire male jack for USB?

author: NiHaoMike
author_rank: Super Contributor
timestamp: November 10, 2018, 07:34:21 pm
content: The main problem with using the 3.5mm connector for anything that has power is that it momentarily shorts when connected/disconnected. But it has been done - the iPod Shuffle (except the original that has a standard USB plug built in) does just that.

author: rakeshm55
author_rank: Regular Contributor
timestamp: November 11, 2018, 04:30:41 am
content: Quote from: Richard Crowley on November 10, 2018, 12:38:37 pmChasis circular connector is user accessible external connectorInternal board to front panel via a flat ribbon cable...cable not shielded ..length will be 6inch max...both side will have a 0.1inch header...circular connector soldered to front panel....External connector will be fischerhttps://www.fischerconnectors.com/global/en/products/ultimate

author: james_s
author_rank: Super Contributor
timestamp: November 11, 2018, 04:46:12 am
content: Quote from: 001 on November 10, 2018, 03:38:53 pmBecause using the same connector for multiple different standards is stupid. You don't want 5V with the ability to deliver 1A or more on the same connector you plug headphones and other AV stuff into.

author: 001
author_rank: Super Contributor
timestamp: November 11, 2018, 08:55:50 am
content: Noheadphones use TRS jack

author: bob225
author_rank: Frequent Contributor
timestamp: November 11, 2018, 11:53:04 am
content: Quote from: 001 on November 11, 2018, 08:55:50 amyou never used a headset or a mic/earphones that are supplied with a lot of phones all use TRRS even if you do put in a TRS jack into a TRRS socket your have a resistive short avg of 25 ohms but can be 8 to several hundred ohms (apple earbuds are 23 omh's iirc)

author: Richard Crowley
author_rank: Super Contributor
timestamp: November 11, 2018, 11:57:12 am
content: Quote from: 001 on November 11, 2018, 08:55:50 amNo. TRRS is widely used in phones and computers to accomodate microphone.And even if they used TRS, it would still be a terrible idea because the USB power would blow out most headphones, etc.

author: 001
author_rank: Super Contributor
timestamp: November 11, 2018, 02:34:43 pm
content: Quote from: Richard Crowley on November 11, 2018, 11:57:12 amHa-ha-haDid You mean telephones? Nobody connect headphone to telephone. All telephones has it own speaker

author: Twoflower
author_rank: Frequent Contributor
timestamp: November 11, 2018, 03:13:49 pm
content: I use my cellphone with both: TRRS (a.k.a. Headset) and TRS (a.k.a. Headphone); they are compatible. Except I had a Headset that worked fine with Fruit-Phones but not with Robotic ones, but that's another story. So having another 3.5mm jack nearby you suggest to use for USB will likely fry the audio-stage or a protection circuit needs to be implemented (adding $). I know that such things existed in the past. Also other way around is possible: USB-C allows alternative usage on certain pins. But that's by design.And with the ever faster running USB you can't use such connectors signal integrity wise anymore. Even the USB 2.1 pins are not used for USB 3 modes because the signal integrity. And you would need a TRR...RRS connector ;-). About the signal integrity I wonder all the time about the RJ-45 and Ethernet.

author: Richard Crowley
author_rank: Super Contributor
timestamp: November 11, 2018, 05:20:54 pm
content: Quote from: 001 on November 11, 2018, 02:34:43 pmSince you have deliberately obscured your location, we don't know what planet you are posting from. Here on planet Earth, 100s of millions of people use TRS and TRRS headsets, earbuds, etc. every day. What do they use there on your planet?

author: T3sl4co1l
author_rank: Super Contributor
timestamp: November 11, 2018, 08:34:54 pm
content: FYI, I suspect 001 is trolling...Tim

author: Twoflower
author_rank: Frequent Contributor
timestamp: November 11, 2018, 08:40:27 pm
content: Quote from: T3sl4co1l on November 11, 2018, 08:34:54 pmIn retro perspective: You're probably right. And I fell for it...

author: Buriedcode
author_rank: Super Contributor
timestamp: November 11, 2018, 08:42:38 pm
content: Quote from: ConKbot on November 09, 2018, 02:34:52 pmAnd those rarely run at high speed, not without errors. It doesn't matter how expensive the case is, front panel connectors and the cabling will be the cheapest you can get. The exception is with USB 3.0 which actually uses a USB 3.0 cable to connect to the motherboard. But I have yest to find a PC where the front panel USB 2.0 connectors allow for high speed.

author: Richard_L
author_rank: Contributor
timestamp: November 11, 2018, 11:42:05 pm
content: Quote from: Gyro on November 09, 2018, 01:26:07 pmThe USB to RJ45 cable that APC insist on using for communication with many of their UPSs is in widespread use for reasons I don't understand (and the use of RJ45 surely fails to satisfy the V and GND first rule).(Try not to look at the price, btw)https://www.apc.com/shop/uk/en/products/UPS-Communications-Cable-Simple-Signalling-USB-to-RJ45/P-AP9827?isCurrentSite=true

author: Monkeh
author_rank: Super Contributor
timestamp: November 12, 2018, 01:42:11 am
content: Quote from: Buriedcode on November 11, 2018, 08:42:38 pmI.. have yet to encounter a reasonable one which doesn't.I've put many terabytes through front panel USB ports on my own machines.

author: Buriedcode
author_rank: Super Contributor
timestamp: November 12, 2018, 01:46:30 am
content: Quote from: Monkeh on November 12, 2018, 01:42:11 amThen I'd like to know which case manufacturer you use. I don't really need >35MB/sec, I can just use the rear ports if I need ~50MB/sec, but I have never been able to use phones MPT reliably using front panel ports.

author: Monkeh
author_rank: Super Contributor
timestamp: November 12, 2018, 02:00:48 am
content: Quote from: Buriedcode on November 12, 2018, 01:46:30 amAntec, Silverstone, Coolermaster, Corsair, Fractal, NZXT, prebuilts from Dell, HP, Lenovo, 3.5" modules from various brands including cheapo card readers, Silverstone is the only one I remember..

author: NiHaoMike
author_rank: Super Contributor
timestamp: November 12, 2018, 02:44:17 am
content: Quote from: Richard_L on November 11, 2018, 11:42:05 pmThe price is the reason why - they want to sell the overpriced cables! They also use a modified RJ45 to prevent crimping your own.