M.2 B-Key slot has the key notch at pins 12-13 providing SATA, USB 3.0, and PCIe x2 interfaces. Used for SATA SSDs, cellular modems (with SIM), and USB-based storage in compact form factors.
| Pin | Name | Function | Type |
|---|---|---|---|
| 1 | GND | Ground | GND |
| 2 | 3.3V | 3.3V power | PWR |
| 5 | TX+ | SATA TX positive | BUS |
| 6 | TX- | SATA TX negative | BUS |
| 7 | RX+ | SATA RX positive | BUS |
| 8 | RX- | SATA RX negative | BUS |
| 41 | USB3 TX+ | USB 3.0 TX positive | BUS |
| 42 | USB3 TX- | USB 3.0 TX negative | BUS |