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I am trying to hard wire a USB host to a slave, but i don't know if there is maybe a data line switch that would be there if I used a USB cable. I thought I might have to because I looked at some USB wiring and if a USB cable was wired so that the wiring stayed the same along a line:

+5v ------------------------- +5v  
 D+ ------------------------- D+  
 D- ------------------------- D-  
GND ------------------------- GND

But then you put the USB ports in the same orientation beside each other the wiring is reversed:

+5v ----------------┐
 D+ --------------┐ |
 D- ------------┐ | |
GND ----------┐ | | |
GND ----------┘ | | |
 D- ------------┘ | |
 D+ --------------┘ |
+5v ----------------┘

So I wondered if maybe the lines were reversed in cables

I know with RX and TX lines on serial device that RX connects to TX and TX connects to RX, so that encouraged my wondering

I did some looking online and some places vaguely implied I might be right, but I wasn't sure.

So what do you think?

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  • \$\begingroup\$ This is one of the reasons why USB-A to USB-A cables are outlawed in the spec. The connection scheme you propose doesn't make any sense and is not a supported configuration. \$\endgroup\$
    – brhans
    Jan 26, 2022 at 17:28
  • \$\begingroup\$ the two diagrams are the same \$\endgroup\$
    – jsotola
    Jan 26, 2022 at 19:47
  • \$\begingroup\$ @jsotola that was the point. i wanted to demonstrate that if the wiring in the cord was connecting contact to contact in a straight line, the labeling had reversed, which was the inspiration for my question. \$\endgroup\$
    – ShortsKing
    Jan 26, 2022 at 21:10
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    \$\begingroup\$ @ShortsKing diagrams do not represent the physical pinout if pin numbers are not included, nor do they represent the physical orientation of the cable ... the second diagram does not represent a bent cable, and the first diagram does not represent a straight cable ... the second diagram actually represents jumpers on a single 8 pin connector \$\endgroup\$
    – jsotola
    Jan 26, 2022 at 21:26

2 Answers 2

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D+ and D- stand for polarity of the differential pair. They shouldn't be reversed.

In your diagram the opposite ends should have the connectors upside down to eachother.

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USB wires are never reversed, it would not work.

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