USB-C is a reversible connector with 24 contacts in two rows. Besides power and USB 2.0 data, it carries four high-speed SuperSpeed pairs for USB 3.x, USB4 or DisplayPort, and two CC configuration pins through which devices negotiate voltage and current with the charger.
For electronics, the CC pins matter most: a board that only needs to draw power from USB-C needs a 5.1 kΩ resistor to ground on each of them. Without them, a USB-C charger won’t power it.
Key specs
- 24 contacts in two rows (A1–A12 and B1–B12), 0.5 mm pitch
- reversible – plugs in either way up; the device detects the orientation via the CC pins
- VBUS power 5 V up to 3 A, with USB Power Delivery up to 48 V and 240 W
- USB 2.0 (D+ and D−), SuperSpeed (USB 3.x, USB4) and alternate modes (DisplayPort)
- receptacles with 24 pins (full), 16 pins (USB 2.0 only) and 6 pins (power only)
USB-C Receptacle Pinout
The receptacle is drawn looking into the opening – the top row of pins is A1–A12 from the left, the bottom row B12–B1. Use the filter to show which pins a USB 2.0-only or power-only receptacle has.
| Pin | Signal | Note |
|---|---|---|
| A1 | GND | Ground |
| A2 | TX1+ | SuperSpeed – transmit, pair 1 (USB 3.x, USB4, DisplayPort) |
| A3 | TX1− | SuperSpeed – transmit, pair 1 |
| A4 | VBUS | Power: 5 V, up to 48 V with USB Power Delivery |
| A5 | CC1 | Configuration channel – cable orientation, source current, USB PD. Device: 5.1 kΩ to GND |
| A6 | D+ | USB 2.0 – spojit s B6 |
| A7 | D− | USB 2.0 – spojit s B7 |
| A8 | SBU1 | Sideband channel for alternate modes (DisplayPort AUX), otherwise leave unconnected |
| A9 | VBUS | Power: 5 V, up to 48 V with USB Power Delivery |
| A10 | RX2− | SuperSpeed – receive, pair 2 |
| A11 | RX2+ | SuperSpeed – receive, pair 2 |
| A12 | GND | Ground |
| B1 | GND | Ground |
| B2 | TX2+ | SuperSpeed – transmit, pair 2 |
| B3 | TX2− | SuperSpeed – transmit, pair 2 |
| B4 | VBUS | Power: 5 V, up to 48 V with USB Power Delivery |
| B5 | CC2 | Configuration channel – device: its own 5.1 kΩ to GND (not shared with CC1) |
| B6 | D+ | USB 2.0 – spojit s A6 |
| B7 | D− | USB 2.0 – spojit s A7 |
| B8 | SBU2 | Sideband channel for alternate modes, otherwise leave unconnected |
| B9 | VBUS | Power: 5 V, up to 48 V with USB Power Delivery |
| B10 | RX1− | SuperSpeed – receive, pair 1 |
| B11 | RX1+ | SuperSpeed – receive, pair 1 |
| B12 | GND | Ground |
Resistors on the CC Pins
The source (charger, computer) applies voltage to VBUS only when it sees a sink on one of the CC pins – a 5.1 kΩ Rd resistor to ground. In turn, the source uses the value of its Rp resistor to the supply to advertise how much current it can deliver.
| Resistor | Where | Value | Meaning |
|---|---|---|---|
| Rd | device – CC1 and CC2, each separately to GND | 5.1 kΩ | “I’m a sink” – the source turns on 5 V |
| Rp | source – to 5 V | 56 kΩ | default USB current (500 or 900 mA) |
| Rp | source – to 5 V | 22 kΩ | source supplies 1.5 A |
| Rp | source – to 5 V | 10 kΩ | source supplies 3 A |
| Rp | USB-A → USB-C cable | 56 kΩ | that’s why a board without Rd works with such a cable but not with a USB-C charger |
Each CC pin needs its own resistor. The first revision of the Raspberry Pi 4 had CC1 and CC2 tied together through a single one – with e-marked cables, the charger didn’t recognize it as a sink and didn’t power it.
16-Pin and 6-Pin Receptacles
Cheap boards with ESP32, RP2040 or Arduino usually have a USB 2.0-only receptacle with 16 contacts – it lacks the TX and RX pins. The outer GND and VBUS contacts are often merged into shared pads, so the board has only 12 terminals. A power-only receptacle (6 pins) has just VBUS, GND, CC1 and CC2 (contacts A5, A9, A12, B5, B9, B12) – no D+ and D− at all.
- D+ and D− appear twice in the receptacle (A6 and B6, A7 and B7) – connect them on the board, otherwise USB works in only one cable orientation.
- Leave SBU1 and SBU2 unconnected unless you use an alternate mode.
- All VBUS pins and all GND pins should be connected together on the board.
What to watch out for
- Without 5.1 kΩ resistors on CC1 and CC2, the board gets power only from a USB-A → USB-C cable. Neither a USB-C charger nor a computer with USB-C will power it.
- Don’t tie CC1 and CC2 to a single resistor – each pin needs its own.
- With USB Power Delivery, VBUS can also carry 9, 15 or 20 V, and with Extended Power Range (EPR) 28, 36 or 48 V – but only after negotiation over CC. A board with plain 5.1 kΩ resistors always gets 5 V.
- Cheap USB-C cables often carry only USB 2.0 and power – for fast data or video you need a full-featured cable.
- Current above 3 A (up to 5 A) may flow only through an e-marked cable.
USB-C on chiptron.eu/
More articles about USB-C, charging and cables:
- A third of my cables in the trash – a tester revealed USB-C cables with missing signals
- USB-C myths and nonsense – what isn’t true about the connector
- Raspberry Pi 4 and USB-C chargers – why the first revision didn’t work with all chargers
More pinouts
See all pinouts on the Pinouts page.