USB-A is the classic rectangular USB connector on computers, chargers and hubs. The USB 2.0 version has four pins – 5 V power, ground and the D+ and D− data pair. USB 3.0 and later add five contacts for fast SuperSpeed transfers; you can recognize it by the blue insert.
The wire colors in a USB 2.0 cable are defined by the standard: red VBUS, white D−, green D+ and black GND.
Key specs
- USB 2.0: 4 pins – VBUS (5 V), D−, D+ and GND
- USB 3.x: 5 additional pins – two SuperSpeed pairs and GND_DRAIN ground
- 5 V power: USB 2.0 up to 500 mA, USB 3.x up to 900 mA, charging ports up to 1.5 A
- speed: USB 2.0 up to 480 Mb/s, USB 3.x 5 or 10 Gb/s
- receptacle opening 12.5 × 5.1 mm
USB-A Receptacle Pinout
The receptacle is drawn looking into the opening with the tongue at the top. The USB 2.0 pins are at the bottom, with wire colors; the USB 3.0 pins are at the top.
| Pin | Signal | Wire color | Note |
|---|---|---|---|
| 1 | VBUS | red | 5 V power – USB 2.0 up to 500 mA, USB 3.x up to 900 mA, charging port (BC 1.2) up to 1.5 A |
| 2 | D− | white | USB 2.0 data (differential pair with D+) |
| 3 | D+ | green | Data USB 2.0 |
| 4 | GND | black | Ground |
| 5 | SSRX− | – | USB 3.x – SuperSpeed receive (from the host's point of view) |
| 6 | SSRX+ | – | USB 3.x – SuperSpeed receive (from the host's point of view) |
| 7 | GND_DRAIN | – | SuperSpeed signal ground (shielding of the pairs in the cable) |
| 8 | SSTX− | – | USB 3.x – SuperSpeed transmit (from the host's point of view) |
| 9 | SSTX+ | – | USB 3.x – SuperSpeed transmit (from the host's point of view) |
Wire Colors in a USB Cable
When repairing or shortening a USB 2.0 cable, go by the colors:
| Pin | Signal | Wire color | Meaning |
|---|---|---|---|
| 1 | VBUS | red | +5 V power |
| 2 | D− | white | data − |
| 3 | D+ | green | data + |
| 4 | GND | black | ground |
| shell | shield | braid or bare drain wire | connects to the metal connector shell |
Cheap charging cables often have no data wires at all. For the SuperSpeed wires, USB 3.0 specifies the colors SSRX− blue, SSRX+ yellow, SSTX− purple and SSTX+ orange, but manufacturers choose them differently – for those, rely on measurement.
Charging Ports
Chargers following the BC 1.2 standard have the D+ and D− pins shorted together. This tells the device it doesn’t have to wait for a computer, and it draws up to 1.5 A. Apple chargers and fast charging (Quick Charge) use other voltages on the data pins.
What to watch out for
- Watch the order on the cable plug: viewed from the front, the pins are mirrored (4, 3, 2, 1).
- D+ and D− are a differential pair – route them together and at equal length.
- A computer port supplies only limited current (USB 2.0: 500 mA) – power motors and LED strips from a separate supply.
USB on chiptron.eu/
Also on chiptron.eu/:
- FNIRSI FNAC-28 USB tester – measuring voltage, current and power while charging
- CH340E – a cheap USB-UART converter for programming boards
More pinouts
See all pinouts on the Pinouts page.