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USB - Signaling
By admin | April 29, 2007
USB Signaling:
Pin numbers (looking as a socket):
| Pin assignments | ||
| Pin | Function | |
|
|
1 | Vbus (4.75 - 5.25 V) |
|
|
2 | D- |
|
|
3 | D+ |
|
|
4 | GND |
|
|
Shell | Shield |
USB signals are transmitted on a twisted pair of data cables, labelled D+ and D−. These collectively use half-duplex differential signaling to combat the effects of electromagnetic noise on longer lines. D+ and D− usually operate together; they are not separate simplex connections. Transmitted signal levels are 0.0–0.3 volts for low and 2.8–3.6 volts for high.
Mini-USB Signaling:
USB Mini-A (left) and -B (right) plugs, showing pin numbers:
USB Mini-A and -B plugs (pictures):
| Mini-USB connector pinout | |
| Pin | Function |
| 1 | Vbus (4.75 - 5.25 V) |
| 2 | D- |
| 3 | D+ |
| 4 | ID |
| 5 | GND |
Most of the pins of a Mini-USB connector are the same as those in a standard USB connector, except pin 4. Pin 4 is called “ID” and, in the Mini-A connector, is connected to ground, but in the Mini-B is not connected. This causes a device supporting USB On-The-Go (with a Mini-AB socket) to initially act as host when connected to a USB Mini-A connector (the “A” end of a Mini-A–Mini-B cable). The Mini-A connector also has an additional piece of plastic inside to prevent insertion into a slave-only (B-only) device.
Source: http://en.wikipedia.org/wiki/Usb
Topics: Computers & Software |