# Replacing USB-A with USB-C fails [closed]

What I did, step by step:

1. Cut off the USB-A cable from a device. (smart card reader)

2. Cut a USB-C to USB-A cable in half. (cable came with a phone)

3. Soldered the USB-C part (see step 2) to the device (see step 1):

4. Connected the device to my phone: It was not detected. (lsusb in Termux)

5. Cut a USB-A to Micro cable in half.

6. By soldering, replaced the USB-C cable with the USB-A cable from step 5. (In case you wonder: I could’ve used the original cable from step 1, but that was already destroyed as I tore it apart – see below.)

7. Connected the device to my phone using a USB-C to A adapter. Now it worked.

What did I do wrong?

Now I read in an answer that one should do some connections via a resistor. However:

• I tore the cable from step 2 apart:

• The USB-A part contains no resistor. Furthermore the colors of the wires exactly matched the standard USB-A pin out.

• The USB-C part contains some electronics. There is a component labeled D9 and another very tiny component possibly labeled R1. It looks like that tiny component bridges the white and the green wire. It’s hard to see because it is all covered in glue which is almost impossible to peel off.

• On the web, I found advertisements for USB-C to USB-A cables that mention the resistor being part of the USB-C plug. I assume this is standard practice.

I don’t understand what went wrong. The solder connections were certainly good. In fact I redid them, then tried again, got the same result. Also I was very careful not to short any connections, except for intentionally shorting the two black wires once: no difference

## closed as unclear what you're asking by Chris Stratton, winny, RoyC, Sparky256, Voltage SpikeAug 28 '18 at 17:19

Please clarify your specific problem or add additional details to highlight exactly what you need. As it's currently written, it’s hard to tell exactly what you're asking. See the How to Ask page for help clarifying this question. If this question can be reworded to fit the rules in the help center, please edit the question.

• This is unanswerable, as you've provided no meaningful documentation of what you did. Just about anything could be wrong. One thing that does stand out is that you seem to have assumed the wires in the donor cable and device consistently followed some norm of color code, when in practice is no consistently followed standard for this. If you want to actually solve this, document which contact in the connector was connected to which signal role on the board. – Chris Stratton Aug 21 '18 at 13:20
• Also to debug a faulty USB device look in dmesg output. No response often indicates a power problem or disconnected data wires. A full speed device failing to enumerate as low speed or a low speed device failing to enumerate as full speed often indicates swapped data wires (ie, the detect pullup on the wrong line) – Chris Stratton Aug 21 '18 at 13:24
• @ChrisStratton I didn’t mention, but I did tear apart the original cable as well. The colors matched the colors in the other cables. – feklee Aug 21 '18 at 13:38
• @feklee - While it may not be your issue here, just because you had the same variety of colors doesn't mean their roles match. Unless you actually verify that with an ohm meter to the connector contacts, it's not a safe assumption, and when something goes wrong, you have to check all the assumptions. I've seen black be VBus and red be Ground. Cables aren't designed to be cut up, so making sure the machine gets loaded with the theoretically right color rolls in the right places isn't really a priority. – Chris Stratton Aug 21 '18 at 13:40
• @ChrisStratton I did tear everything apart, incl. the plugs (lots of glue) till I could visually see the connections of the cables to the pins. It was all consistent in all the cables. Still, thanks for mentioning that the colors should not be trusted! – feklee Aug 21 '18 at 13:44