Can I use a male a to male a USB cable to power a power module? - Page 1
Forum section: electronics / beginners

author: Ram80
author_rank: Contributor
timestamp: May 21, 2024, 09:03:13 am
content: The title pretty much says it all. Can you use a male A to male A USB cable to power a supply power module from say a phone charger plug?

author: abeyer
author_rank: Frequent Contributor
timestamp: May 21, 2024, 02:51:58 pm
content: Quote

author: ataradov
author_rank: Super Contributor
timestamp: May 21, 2024, 03:39:03 pm
content: Male A to male A cables are illegal in the USB spec for a good reason. USB 3 spec does define a cable like this, but in that case USB2 data lines and VBUS are not connected. And most USB A to A cables you see on the market don't follow that, so they are really dangerous. Avoid them entirely to eliminate the risk of damaging your stuff.

author: thm_w
author_rank: Super Contributor
timestamp: May 21, 2024, 11:48:08 pm
content: Which power supply module specifically are you talking about that would take power from a USB A port?

author: ArdWar
author_rank: Frequent Contributor
timestamp: May 22, 2024, 01:45:22 am
content: Are there any remotely legit non janky ass hardware that need (and properly justify) the use of male A to male A USB?

author: ataradov
author_rank: Super Contributor
timestamp: May 22, 2024, 01:57:08 am
content: I have not seen any real marketable products.The only time I've seen the need for a cable like this is with CH569 evaluation kits. The device supports SuperSpeed, but they did not want to bother including the mux, so they used USB-A on the device side to make sure orientation is fixed. This device would be so much better if that mux was part of the silicon.

author: K5_489
author_rank: Regular Contributor
timestamp: May 22, 2024, 05:08:49 am
content: Quote from: ArdWar on May 22, 2024, 01:45:22 amI've got several A-A cables that were included with industrial computer monitors that were installed in our work trucks (yes, somehow our company safety rep signed off on installing steel cased monitors inside the cabs of service trucks. No, I don't know what they were smoking at the time). IIRC, they were intended to be used to program some low level features in the monitors via the same USB ports normally used for connecting other USB peripherals. I saved the A-A cables as a future "just in case", but have never found a need for them.Though I suppose this would fall under "janky ass hardware", as it does seem strange to use USB controllers that can act as both host and client on something as large as a monitor that could have easily just has another dedicated connector for this purpose that also likely would have been cheaper anyways.I also have an old Android car stereo head unit (not just an Android Auto capable thing...actually runs Android right on it, like a tablet strapped to an amplifier in one case) that apparently can be connected to via one of the external USB-A ports via an A-A cable for re-flashing the ROM in the event of the thing getting bricked, but I was never able to get that part to work....or I just bricked it REALLY hard, lol.

author: ataradov
author_rank: Super Contributor
timestamp: May 22, 2024, 05:20:41 am
content: Doing it for service uses like that makes some sense, especially if maintenance is to be performed by trained people. If the device is normally a host, it would have USB-A connector. Putting another one may be too much effort and may be confusing to the end users. In that case device may be put into a device role in the service menu, so the VBUS conflicts would be avoided.Although it is still extremely jank, since once time you forget to put it into that mode, you are going to fry something.Plus existence of the A-A cables is a puzzle on its own.

author: K5_489
author_rank: Regular Contributor
timestamp: May 22, 2024, 06:18:03 am
content: Quote from: ataradov on May 22, 2024, 05:20:41 amIf the cables were supplied only to the techs, I could see that. But the A-A cable was supplied with every monitor, just like any ol' consumer monitor includes a power cable, with zero documentation for their purpose. Yes, all of them that I didn't keep for curiosity sake went straight to the e-waste bin.Though I recall our buyers found some "screaming deal" on these things direct through the supplier in China, so that may well have something to do with the odd design too. I sent an email to the supplier asking what the cable was supposed to be for, and got a poorly translated reply about it having something to do with service menus. Regardless, we never had a need to mess with them, and never even tried to do anything with them other than plug them in to power and the computer, and use it like any other universal monitor.I was just the guy tasked with putting these nightmares in the trucks, and ended up having to explain why putting a 17" steel cased monitor on the dashboard of a truck right next to the passenger side air bag, held on with four 4mm diameter screws was a REALLY BAD IDEA to management.

author: wraper
author_rank: Unknown
timestamp: May 22, 2024, 06:37:14 am
content: Quote from: ataradov on May 22, 2024, 01:57:08 amStill not a valid reason, there are USB 3.x versions of USB-B and micro USB every sane company used before type C arrived.EDIT: I suppose it's because it can be used as host, which you didn't make clear.

author: ataradov
author_rank: Super Contributor
timestamp: May 22, 2024, 06:51:00 am
content: SuperSpeed Micro-B can act as a host too via regular OTG ID pin of the old Micro-B part of the connector. But it still sucks. The real solution is to figure out the mux. The product as is is pretty meh, since there is no actually useful reference design. You would expect people to want Type-C, so reference design must include that.But like everything with WCH, it is an interesting device, but with half-baked ecosystem. The documentation for the SS USB just says to look in the example source code.

author: perieanuo
author_rank: Frequent Contributor
timestamp: May 22, 2024, 09:48:38 am
content: we can't decide without knowing how much inrush current the module needs. lot of usb laptop outputs wil trigger the protection or just dye if you need high current at start.you can consult some docs un usbx specs to see where you are.generally, lot of us are using this approach with dev boards, so maybe yes will do it, but devil is in the details

author: rsjsouza
author_rank: Super Contributor
timestamp: May 22, 2024, 12:31:41 pm
content: As others have said, it is not recommended to use such cable to avoid crapping out things when you are distracted or tired.As for examples, quite a few old cheap kits used these and even test gear auch as Owon's VDS1022i oscilloscope and Intronix Logicport Logic Analyzer. Not amusing.

author: abeyer
author_rank: Frequent Contributor
timestamp: May 22, 2024, 05:51:19 pm
content: Your cryptic screenshot with no description isn't very helpful... but given what it shows I think what you're trying to do doesn't even make sense.AFAIK, all of those little breadboard modules with usb a ports aren't intended to be poweredfromthe usb, they are wired toprovidepower on that usb port from the regulated supply that is powered from the barrel jack.

author: thm_w
author_rank: Super Contributor
timestamp: May 22, 2024, 09:49:43 pm
content: Quote from: abeyer on May 22, 2024, 05:51:19 pmSo, the real intention of the OP here was to power a breadboard via USB. Which can be done by either:- soldering some header pins to a USB cable- buying a board that has USB inputs (https://www.aliexpress.us/item/2251832692442589.htmlorhttps://www.aliexpress.us/item/3256804007223005.htmletc).

author: aeberbach
author_rank: Regular Contributor
timestamp: May 22, 2024, 10:49:03 pm
content: The Agon Light Z80 homebrew computer required an A-A cable in its original form. It was annoying to have just one of them.I also would be very careful powering a breadboard via USB. If you power it from your computer you are asking for it, you will almost certainly end up with a couple of fried USB ports. If you power it from an adapter is it one you can trust with a right-side failure if you connect it wrong, or was it real cheap on Amazon?

author: kevin.gibbs
author_rank: Regular Contributor
timestamp: August 14, 2024, 04:27:44 am
content: Usually, the power supply module sends voltage through this connector but does not receive it.By the way, which specific power supply module are you referring to?

author: radiolistener
author_rank: Super Contributor
timestamp: August 14, 2024, 08:19:44 am
content: If the board which you want to power supports power for USB, why not. I don't see any obstacles for that.But be careful if your device has it's own power, in such case it may lead to issues.Quote from: Ram80 on May 22, 2024, 11:47:57 amOhh... don't afraid, you can connect this board with no doubt.As I remember, I tried to connect external power to almost any pins of this boardBut the best result with direct solder to connectors pins, in this case there is min voltage drop.Be careful with short circuit, these boards have cheap LDO which can burn out if you make short circuit.I suggest to replace its LDO with genuine one from ST or other brand with internal protection from short circuit.I soldered thick wires with mains socket directly to USB connector and using to connect to my lab PSU. Mains socket ideally fits with it's terminal. In that way I can power high power USB devices with USB connector from my lab PSU

author: mtwieg
author_rank: Frequent Contributor
timestamp: August 14, 2024, 12:09:21 pm
content: Recently had to argue down a coworker from using the forbidden cable in a product. The cable would connect different components within the product, not to the outside world, so they thought it wouldn't hurt. But he did require all lines to be connected (including Vbus). It didn't bother him that he was relying on a cable that doesn't comply with the standard.Play stupid games, win stupid prizes.

author: Ranayna
author_rank: Super Contributor
timestamp: August 14, 2024, 02:32:54 pm
content: I had a keyboard with a removable A to A USB cable some time ago.A product of a well known PC periphal manufacturer, Corsair i think.This was pre USB-C, but who knows why they didn't use a B plug on the keyboard side.

author: thm_w
author_rank: Super Contributor
timestamp: August 14, 2024, 11:25:42 pm
content: Quote from: mtwieg on August 14, 2024, 12:09:21 pmThe issue is not standards compliance, its inside the product so it really does not matter. Plenty of major products use internal custom USB to JST or some other non-standard format.The issues in this case:- Using a cable that can easily be incorrectly connected, assuming you will ever have more than one peripheral component.- Stocking a useless cable - stocking A to B or A to C cable more likely to have some value elsewhere.- Sourcing/costing - A to A might be slightly more expensive or harder to source, though not massively

author: radiolistener
author_rank: Super Contributor
timestamp: August 16, 2024, 06:09:54 am
content: Forgot to mention, that if you're using USBA to USBC cable it may consists some kind of chip inside which prevents using it in USBC to USBA direction.So, if you're planning to use USBA to USBC cable to connect USBA side to your board and USBC to the charger, it may won't work with such smart-cable.You can detect these smart-cables with DMM, they have about 61 kΩ resistance between VCC and GND lines on the cable.