USB-C "card edge" connector. Yay or nay? - Page 1
Forum section: electronics / projects

author: BadeBhaiya
author_rank: Regular Contributor
timestamp: May 15, 2025, 08:54:50 am
content: In a fit of passion (and probably dunning kruger), I brought up the idea of using USB-C compatible card edge connector for connecting our PC board panels to the programming interface to program all 9 boards in one go. It makes sense, there are 24 conductors in a USB-C to USB-C cable (reversibility be damned).I could theoretically have (5 row x 2 col) 10 boards in a panel and be able to program them using SWD (2 lines per board, so 20 total) by using a single USB-C cableIt sounds good but I do wonder how easy is it to buy actually decent USB-C cables with all 24 conductors in them? Would it be better to use HDMI instead (19 conductors, so max 8 boards, fab house won't mind) since its a lot larger physically so it'll be easier to align?I'm sure a lot of you have done this before

author: ataradov
author_rank: Super Contributor
timestamp: May 15, 2025, 09:07:04 pm
content: None of the cables have all 24 connectors. They all have much smaller subset and reversing relies on the detection of the orientation.You can still use the connector itself, of course, but you will have to make custom cables. They would not need to be anything special for a test/programming setup.

author: BadeBhaiya
author_rank: Regular Contributor
timestamp: May 15, 2025, 09:39:28 pm
content: Thanks for the response Alex. I don't really want to mess with custom cabling to be honest, so I'll take the easy way out and reduce the board on the panel. Any idea what's the most number of conductors USB-C cables come with?I do recall seeing a project of yours which used a similar USB-C PCB only footprint. Or am i misremembering?

author: tszaboo
author_rank: Super Contributor
timestamp: May 15, 2025, 09:39:51 pm
content: I believe there is a special place in hell for people who use USB connectors for some other protocol. My favorite was this guy who used mini USB (because it's very rare you see) for RS232 that killed any port you plugged into.

author: BadeBhaiya
author_rank: Regular Contributor
timestamp: May 15, 2025, 09:48:35 pm
content: Don't worry, l fully plan on filing the silkscreen with enough warnings to fill a dozen books

author: wraper
author_rank: Unknown
timestamp: May 15, 2025, 10:06:23 pm
content: Why not mini HDMI (there is also micro but I do not suggest due to generally fragile cable side connector) or mini DP? You get more wires, no orientation problem and much lower chance of someone plugging a standard device into it.

author: BadeBhaiya
author_rank: Regular Contributor
timestamp: May 15, 2025, 10:19:34 pm
content: I'm all open to suggestions. I don't have any reason to specifically choose USB-C, it just happens to be a very common type of cable, ubiquitous i might say.

author: wraper
author_rank: Unknown
timestamp: May 15, 2025, 10:41:16 pm
content: Quote from: BadeBhaiya on May 15, 2025, 10:19:34 pmWhich is exactly why you should avoid it. Not to say there are different types of cables, quite a few of them with built-in electronics.

author: Wolfram
author_rank: Frequent Contributor
timestamp: May 16, 2025, 06:29:23 am
content: Quote from: tszaboo on May 15, 2025, 09:39:51 pmThat's a good one. My favorite is some Variant/Agilent turbo pump controllers that use a USB-B connector to for 24V to power fans. One example is the Turbo V81

author: ftg
author_rank: Frequent Contributor
timestamp: May 16, 2025, 06:48:26 am
content: I'll echo the hope to not use super common connectors with dangerous pinouts.I have worked on products where it was decided to reuse common, cheap connectors.So there were RJ45's with everything from +24VDC to 5V and USB available on them and mixing them up did cause damage.USB or USB-C would be very tempting for folks to plug into their computer.My suggestion would be that if one were to use it, the pinout should be of such type that no damage will occur if it is plugged in.

author: Haenk
author_rank: Super Contributor
timestamp: May 16, 2025, 08:13:03 am
content: Quote from: tszaboo on May 15, 2025, 09:39:51 pmNot only USB. Plenty of fun with DB and RJ45 as well. I might even have one of those Apple LaserWriter 10/600 PCI cards with a DB25 port, which is "something", but neither Serial nor Centronics

author: BadeBhaiya
author_rank: Regular Contributor
timestamp: May 16, 2025, 08:55:36 am
content: Just to reiterate, I am panning on putting the repurposed USB-C connector on our custom programming and testing interface board. The panels don't have an actual connector but a board edge connector, something like the picture below, just for USB-C.If I make sure there are enough warnings, and the programming board never leaves the room its being used in, how bad of an idea would it be?

author: ataradov
author_rank: Super Contributor
timestamp: May 16, 2025, 12:57:53 pm
content: It is still not clear how you will do this. Your panel would have to be very thin to fin into the connector, so this limits the boards you can test this way. And then you will be killing connectors on the cables if you don't chamfer the edge, which is a production cost increase for no real reason. And even if you chamfer it, it would still kill the connectors rather quickly.This makes no sense on many levels. Use appropriate connectors. There is almost zero benefit you are deriving from using standard connectors here.

author: coromonadalix
author_rank: Super Contributor
timestamp: May 16, 2025, 01:42:25 pm
content: create your own design if you want, with keyed notch to be sure it is not confused with others ... even if you have the same data lines, com lines, lan lines ...at least build a test plug to convert them back to usb lan serial connectors / industry standards if you do some test benchs, repairs etc...we use 2x rs485 coms on a pci-e 1x connector, the problem is :i'm able to find pci-e 1x cable extenders to do bench tests, but they need to be pin for pin (rarer but exists), not grouped as many, for the supply lines, if not i have a shorted out supply line, luckily it accept shorts ...that's why standard ones is more useful than your proprietary designs ... but don't support frequent connect disconnect, we had many usb-c connector problems, the pcb is very thick, the usb-c plug had shorted power pins, we had to change our designs and try other usb-c typemy 2 cents