I have been trying to figure out how to custom wire a USB-C to USB-A cable for a while, with no luck.

I have tried some different connectors, but wanted to get some outside ideas on what I might be doing wrong. I am not trying to make a high-speed USB-C, so I'm trying to make the connection with just a 4-core wire (GND, D-, D+, VBUS). On a few attempts, I tried pulling the ID pin up with a 56k resistor with no luck. (On a different kind of connector not shown here).

I contacted the manufacturer of one connector style that I have (images below) to get their assistance, but I am still having issues. So my question is:

How would y'all wire this connector to a USB-A (2.0) so it works properly? Thank you! (PS: I am told that the connector has a 56k resistor built-in)enter image description here

enter image description here

  • \$\begingroup\$ What kind of USB cable are you trying to make? Type-C to Type-A plug, or Type-C to Type-A receptacle? \$\endgroup\$ – Ale..chenski Sep 7 '17 at 5:38
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    \$\begingroup\$ Is this cable for data or charging? \$\endgroup\$ – Eisen Faust Sep 7 '17 at 5:57
  • \$\begingroup\$ @EisenFaust --- Mostly, the cables I make are to connect a keyboard to a CPU. So it's mostly about some pretty low-flow data. Some keyboards with onboard USB ports or lots of LEDs, for example, do require more power though. \$\endgroup\$ – rockwell Sep 7 '17 at 12:50

There are two types of Type-C to Type-A cables, one is Type-C to Type-A plug, and another is Type-C to Type-A receptacle. The cables play two different roles, and must be built differently.

  1. The Type-C to Type-A plug cable is used to connect a legacy USB-A host to modern Type-C device, because the Type-A plug goes only to USB hosts receptacles, and nowhere else. In this case the Type-C end of cable must look like it is USB host, and therefore must have a pull-up to +5V VBUS on CC1 pin. Since the the cable goes to regular USB host with generic capability of 500 mA, the Type-C end of cable must have a 56k pull-up resistor, not 22k, not 10k, to prevent port overcurrent and potential damage to the host.

  2. The Type-C to Type-A receptacle cable is used to connect USB Type-C host to any legacy device like a flash drive with Type-A plug. Other legacy devices would require either extra legacy cable, or a different Type-C legacy cable. To make a Type-C host to act as host, the C-end must look as a device, and therefore must have a 5.1k pull-down on CC pin. Essentially this cable is like a legacy "OTG adapter", it converts Type-C host port into Type-A host port.

  • \$\begingroup\$ Thanks for the thoughtful response again, Ali. I'm definitely working with scenario #1 as you described---a plug cable. I'll keep trying. It would be nice to find a connector that had a generous soldering pad (like the one pictured) for the CC1 pin, but maybe I just have to wire it directly to the pin for now. \$\endgroup\$ – rockwell Sep 7 '17 at 12:40

If you only need USB 2.0 compliance, you solder your connector's A6 pad to your USB-A connector's D+ tab and A7 to the D- tab like the picture suggests. Then, solder the GND and VBUS wires and desolder the two SMD resistors since they are only used for charging negotiation.

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    \$\begingroup\$ Thanks, I will give this a shot. I tried wiring the connector as you described with no luck yet, but maybe that's due to the SMD resistors. I'll work on desoldering those and try again. Thanks for the reply! \$\endgroup\$ – rockwell Sep 7 '17 at 12:37
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    \$\begingroup\$ Hmm, so I desoldered the SMD resistors and it appears to be working normally. Nice! I guess my only concern now is...will the cable/connectors overheat if the cable is used as a charging device since we removed the resistors? \$\endgroup\$ – rockwell Sep 7 '17 at 14:22

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