usb
With reference to this article USB Voltage and Current Tester, it shows a diagram as follows:
May I know if it is the same as the following circuit diagram:
This is because according to the article, they only use the black and red cable.
There is no mention of how should I do with the green and white cable.
If the circuit diagram is wrong, I would appreciate if someone can enlighten me the correct circuit diagram.
Thank you.
red = +5 V
white = D-
green = D+
black = ground
(Page 89 of the USB 2 specification)
edit (after reading the other 649 pages)
OK, that's from the formal specification. Reassuring, isn't it? It can even get you an accepted answer. You can feel it coming: there's a but.
This is from page 94. At first sight it seems to confirm what I said, but then there's that word "typical". So not mandatory? I read some more, and the answer isn't clear. The word "typical" must be the most used word in the spec, and also seems to be used for mandatory specifications:
There's that word again, page 93. Sounds like non-binding, but the text above it does say "should be oriented to allow" (emphasis mine). So "typical" seems to be used for mandatory specifications. Talk about confusion!
Apparently there's only 1 way you can trust: measure it. Compare the wire color with the pin number on the connector. The pin number locations are shown in the drawing and their assignments in the table. I'm 99 % sure that it will agree with the "typical" wiring assignment.
There's just that other 1 %... :-(
Further reading
USB version 2.0 specification (.zip file format, size 19.5 MB)
It's easy to just test the connectivity from the pins on the connector-end of the cable to the bare wires at the other end.
Even a hardware store multimeter is good enough for this test.
Disconnect the cable at both ends. Set your meter to the ohms function.
Touch one probe of the meter to one pin of the connector. Touch the other probe to one of the wires. If the wire is connected to the pin, you'll see (near) zero ohms. Depending on your meter you might also get a beep for continuity.
The pin assignments for the connector are readily available. Here's a picture from Wikipedia:
If your connector is a mini or micro type, those pinouts are also available from the Wikipedia article on USB.
Best Answer
Your diagram seems correct to me. It's not the same as in the instructable. I think that your diagram makes more sense.
The instructable shows that the data wires (red and green) are cut. That means that the USB slave device under test will not be able to communicate with the host. The slave will not behave naturally, if it can't communicate. Also by the USB specification, the slave will not be able to receive more than 100mA supply current. If it the data wires are intact, the slave device will be able to behave naturally.
One more thing. Connect-through the EMI shield around the cable.