USB-C Pinout (24-pin)
The 24-pin USB Type-C receptacle, with the part every DIY project trips over: a USB-C charger stays silent until it sees 5.1kΩ resistors on CC1 and CC2. The pin table, the power rules, and what the cheap breakouts leave out.
The 5.1k rulePin tablePower and CCData pairsFAQ
Three rules before you wire anything.
1. 5.1kΩ from CC1 and CC2 to GND (one each) on anything you plug into a USB-C charger. Without them the charger sees no sink and keeps VBUS off, which is the single most common "my USB-C breakout is dead" cause.
2. VBUS is four pins and GND is four pins. A4, A9, B4, B9 carry power; A1, A12, B1, B12 return it. Connect all of them, they are not spares.
3. Never put voltage on a CC pin. They are 5.5V signalling lines for the charger handshake, not power inputs.
Pin table
Front view of the receptacle, A row above B row. The two rows mirror each other so the cable works in either orientation.
| Pin | Signal | What it does |
|---|---|---|
| A1 | GND | Ground return |
| A2 | SSTX1+ | SuperSpeed transmit pair 1, positive |
| A3 | SSTX1- | SuperSpeed transmit pair 1, negative |
| A4 | VBUS | 5V by default, one of four VBUS pins |
| A5 | CC1 | Configuration channel: 5.1kΩ to GND on a sink |
| A6 | D+ | USB 2.0 data, first orientation |
| A7 | D- | USB 2.0 data, first orientation |
| A8 | SBU1 | Sideband use: audio accessory, DisplayPort AUX |
| A9 | VBUS | 5V by default, one of four VBUS pins |
| A10 | SSRX2- | SuperSpeed receive pair 2, negative |
| A11 | SSRX2+ | SuperSpeed receive pair 2, positive |
| A12 | GND | Ground return |
| B1 | GND | Ground return |
| B2 | SSTX2+ | SuperSpeed transmit pair 2, positive |
| B3 | SSTX2- | SuperSpeed transmit pair 2, negative |
| B4 | VBUS | 5V by default, one of four VBUS pins |
| B5 | CC2 | Configuration channel: 5.1kΩ to GND on a sink |
| B6 | D+ | USB 2.0 data, second orientation |
| B7 | D- | USB 2.0 data, second orientation |
| B8 | SBU2 | Sideband use: audio accessory, DisplayPort AUX |
| B9 | VBUS | 5V by default, one of four VBUS pins |
| B10 | SSRX1- | SuperSpeed receive pair 1, negative |
| B11 | SSRX1+ | SuperSpeed receive pair 1, positive |
| B12 | GND | Ground return |
Power and CC
A USB-C source (charger, laptop, power bank) does not switch 5V onto VBUS just because something is plugged in. It waits for the configuration channel to tell it a sink is present. A sink presents a 5.1kΩ pull-down from each CC pin to GND; a source presents a pull-up instead: 56kΩ for default USB power, 22kΩ for 1.5A, 10kΩ for 3A.
That is why a bare breakout board with no CC resistors does nothing on a C-to-C cable, yet works on a USB-A-to-C cable: the old A plug supplies 5V with no handshake at all. If you are wiring a device, the two 5.1kΩ resistors are the fix.
Data pairs
USB 2.0 data rides on D+ and D- twice, at A6/A7 and B6/B7, so a flipped cable still works. The SuperSpeed pairs are separate: TX1 (A2/A3) pairs with RX1 (B10/B11) at the far end, and TX2 (B2/B3) with RX2 (A10/A11). Cheap USB 2.0-only connectors leave the SuperSpeed pins out entirely, which is fine for an ESP32 or Arduino board and useless for a display.
FAQ
Why does my USB-C charger output nothing?
The charger is waiting for a sink on CC1 and CC2. Put a 5.1kΩ resistor from each CC pin to GND and 5V appears. A USB-A-to-C cable sidesteps the handshake, which is why the same board works there.
How much current can I draw at 5V?
It depends on what the source advertises over CC: 0.5A or 0.9A for a basic port, 1.5A and 3A for higher-power ones, and 5A only with an e-marked cable. Above 5V needs USB Power Delivery negotiation, which requires a PD controller.
What are SBU1 and SBU2 for?
Sideband signals: audio accessory mode and DisplayPort AUX. Plain power and data projects leave them unconnected.
Can I feed 12V in on VBUS?
No. VBUS carries 5V unless a PD contract says otherwise, and feeding a higher voltage into a device expecting 5V destroys it. Boost after the connector, not before it.
Which pins matter for a simple maker board?
VBUS (four pins), GND (four pins), CC1 and CC2 with their 5.1kΩ resistors, and D+/D- if you want USB 2.0 data. That is the whole list for a power-and-serial board.
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