12
Does anyone know where to find a USB Micro-A to USB C cord? (beehaw.org)
submitted 1 year ago by to c/askbeehaw@beehaw.org
28 comments fedilink hide all child comments
 

I wish this was a joke. Bosch used USB Micro-A on some of their e-bike motors to connect to a phone, which is USB C. The only one I've been able to find is the one Bosch made that's like 3 inches long and basically useless.

you are viewing a single comment's thread
view the rest of the comments
[–] 2 points 1 year ago (4 children)

A micro USB-AB port has an extra electrical contact which is shorted together with another pin (probably with ground, but I don't remember) when a USB-A connector is inserted, but left unconnected when a USB-A connector is inserted. Some USB driver chips require this extra pin to be shorted to enter host/master mode.

This is done because to have USB communication one device needs to be the master, and the other the slave. Micro and mini USB cables handle this by having an A type connector on one side and a B type on the other side, and whichever device sees the A side will act as the master.

In OP's case the firmware is probably expecting the device to act as the master, but with a B type connector inserted it's unable to do so.

  • permalink
  • fedilink
  • source
  • parent
  • hideshow 4 child comments
    •
  • [–] [S] 2 points 1 year ago* (last edited 1 year ago) (3 children)

    I wonder if I could make a micro B appear as an A if I could find what pins to short...

  • permalink
  • fedilink
  • source
  • parent
  • hideshow 3 child comments
    •
  • [–] 2 points 1 year ago (2 children)

    I know that you can make a USB mini B connection appear as an USB mini A, because I have seen someone do that. He just made a small ball of aluminium foil and shoved it into the connector. The pins that need to be shorted are next to eachother and at the side (but I don't remember if it was the left or right side), so it was still doable to get it in the right place. Micro USB is internally very similar, so it should be possible there too, but the inside is quite a bit smaller so it'll be a lot harder.

    In your case it might be easier to solder 2 cables together. It is a bit annoying to solder USB cables together because the cables are shielded, but there are only 4 internal wires and the data rates are low enough that it doesn't really matter if the shielding is imperfect. USB OTG cables should have an A type connector, and they are generally relatively cheap and easy to obtain. To get the USB-C connector, use a cable that has a USB 2 type of connector on the other side (regular, mini or micro), to make sure that the cable only has the USB 2 wires (USB 3 cables have extra wires in them, which aren't really feasible to extend).

  • permalink
  • fedilink
  • source
  • parent
  • hideshow 2 child comments
    •
  • [–] [S] 2 points 1 year ago (1 child)

    Any guesses on where to find that info? USB standard info seems to be... challenging to find. Like, I have an easier time navigating and understanding NHTSA or UL standards level of challenging.

  • permalink
  • fedilink
  • source
  • parent
  • hideshow 1 child comment
    •
  • [–] 2 points 1 year ago

    I just searched, and the Wikipedia page on USB contains some basic information. If the connector is facing towards you and the clips to secure the cable are facing down, then the pins are numbered 1-5 from left to right. Pin 4 is the "ID" pin which is used to detect if the A or B type connector is inserted, and pin 5 is the ground. In an A type connector those two pins are bridged, so you'd want to short those two pins together if you want the device you plug it in to see your type B cable as if it has a type A connector (the connector is a slightly different shape, but that doesn't matter, it'll still fit and the ID pin is the only method used to detect the connector type).

    If you short the pins together by inserting something conductive inside the connector then you'll likely also short them to the case, but that shouldn't matter as the case is internally almost always connected to the ground too.

    If you take the route of soldering two cables together, I looked into it a bit more and it's apparently a bigger mess than I anticipated. Hardware manufacturers have always treated the USB specs as more of a suggestion than as fixed standards, and apparently this is by far the worst when it comes to micro USB. Most phones and tablets with micro USB which support OTG use the type B receptacle instead of the AB receptacle, even though according to the standards only the AB receptacle is allowed for a device that can act as the host. The majority of micro USB OTG cables are then designed for such devices and use a type B connector for the host side. So if you use an OTG cable to harvest the micro-A connector from, make sure you get a standards-compliant cable. You can see the difference by the shape: for the proper micro-A connector the metal casing on the outside is rectangular in shape, while for the much more common micro-B connector it is roughly trapezoidal. According to the standards the plastic inside the connector should also be white for a type A connector (and black for type B), but those colours are probably the most often violated part of the standards.

  • permalink
  • fedilink
  • source
  • parent