I am working on a project that requires a 5 pin connector but it seems like the USB cable is causing some issues. I am using a microUSB B male-male cord to transfer some power and data. Through further research, I am seeing that Micro USB B may be more complex than a simple 5 wire cord. I found the following quote online:

"Contrary to popular belief, D+ and D- operate together; they are not separate simplex connections."


What does this mean? Is there a way I can use this cable as 5 separate lines?

  • \$\begingroup\$ Usually, the 5th pin on Micro USB is to support USB OTG. This 5th pin is usually grounded at one end of the cable to arbitrate master/slave roles for data transfer between two USB devices. If you're repurposing a USB cable as a general 5-pin cable, I'd check to make sure that pin isn't internally grounded at one end. \$\endgroup\$ – Chris Fernandez Jan 10 '19 at 19:16
  • \$\begingroup\$ The Simplex comment means that when in use, the lines are used as one differential pair - the PC talks to the device, the device talks back, similar to sending/receiving over RS485. Vs RS232, where each side sends on wire and receives on the other. \$\endgroup\$ – CrossRoads Jan 10 '19 at 20:05
  • \$\begingroup\$ you can use the cable as 5 separate wires ..... D+ and D- operate together .... in USB application the two lines are used to transmit a single data signal .... that "joining" is done in the circuitry outside of the cable ..... in the cable itself, the two wires are still electrically separate, so you could use them separately for other applications that do not involve USB \$\endgroup\$ – jsotola Jan 11 '19 at 0:37

You should expect 4 wires in the cable. Ground and the shield will be connected together at one (possibly both) ends. The 5th ID pin is there to tell you what sort of cable it is. The only male to male cables in the standard are OTG cables which will have ID open circuit at one end and connected to ground at the other.

  • \$\begingroup\$ I see thank you for the info. Are the connections you speak of internal in the cable or usually on the board that the cable is connected to? Would it be possible for me to connect the ID to shield and use that as an analog line? or is that bad practice? \$\endgroup\$ – Tapatio Sombrero Jan 10 '19 at 20:36
  • \$\begingroup\$ the connections are made in the cable, they indicate to the device the cable is connected to, what sort of cable it is. The cable will either connect ID to ground and the shield, or leave it unconnected. So yes you could use the connected together ground-id-shield as a signal line, but you'd need to use something else for ground, and as soon as someone accidentally plugs your device into a PC, bad things will happen. \$\endgroup\$ – james Jan 10 '19 at 21:43

Few points to consider:

  1. There is no micro-USB B male-male cords, officially. There are micro-B to micro-A male-male cords. Male-male cords of A-A or B-B type are USB-illegal, and whoever makes and uses these cords are doing a disservice to USB community.

  2. Micro-A-B cables have only 4 signal wires.The ID pin is never implemented within standard cable and is not connected between the ends. The only exception are proprietary short cables for test equipment like "Packet-Master USB-PET Protocol and Electrical Tester".

  3. In a micro-B to micro-A male-male cord the B-end has ID pin unconnected; the A-end has ID pin grounded. The grounding is done locally, in the overmold. This signaling is invented for devices that can act in dual-data role, as devices and as hosts, formerly known as "OTG". These devices are supposed to have so-called micro-A-B receptacle, which can accommodate both B and A plugs. The ID pin informs the device which role it is supposed to assume.

So, no, you can't use any micro USB connectors as a 5-wire interface, there are only 4 wires that propagate from one end to another.


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