Raspberry Pi GPIO 26-pin (P1, Rev2) Pinout
The original 26-pin P1 header on Raspberry Pi 1 Model A/B (Revision 2 layout).
Overview
The 26-pin P1 header is the original Raspberry Pi GPIO connector (Pi 1 Model A/B), two rows of 13 on 2.54 mm pitch. The first 26 pins of the modern 40-pin header are identical to this.
This is the Revision 2 layout: pin 3 = GPIO2, pin 5 = GPIO3, pin 13 = GPIO27 (Rev1 used GPIO0/GPIO1/GPIO21). All GPIO is 3.3 V, not 5 V tolerant.
Pinout
| Pin | Name | Function | Description |
|---|---|---|---|
| 1 | 3V3 | POWER | 3.3 V power |
| 2 | 5V | POWER | 5 V power |
| 3 | GPIO2 (SDA1) | DATA | I2C1 data |
| 4 | 5V | POWER | 5 V power |
| 5 | GPIO3 (SCL1) | CLK | I2C1 clock |
| 6 | GND | GND | Ground |
| 7 | GPIO4 (GPCLK0) | CLK | General-purpose / clock |
| 8 | GPIO14 (TXD) | UART | UART transmit |
| 9 | GND | GND | Ground |
| 10 | GPIO15 (RXD) | UART | UART receive |
| 11 | GPIO17 | SIGNAL | General-purpose GPIO |
| 12 | GPIO18 (PCM_CLK) | SIGNAL | General-purpose / hardware PWM |
| 13 | GPIO27 | SIGNAL | General-purpose GPIO (Rev2) |
| 14 | GND | GND | Ground |
| 15 | GPIO22 | SIGNAL | General-purpose GPIO |
| 16 | GPIO23 | SIGNAL | General-purpose GPIO |
| 17 | 3V3 | POWER | 3.3 V power |
| 18 | GPIO24 | SIGNAL | General-purpose GPIO |
| 19 | GPIO10 (MOSI) | SPI | SPI0 MOSI |
| 20 | GND | GND | Ground |
| 21 | GPIO9 (MISO) | SPI | SPI0 MISO |
| 22 | GPIO25 | SIGNAL | General-purpose GPIO |
| 23 | GPIO11 (SCLK) | SPI / CLK | SPI0 clock |
| 24 | GPIO8 (CE0) | SIGNAL | SPI0 chip enable 0 |
| 25 | GND | GND | Ground |
| 26 | GPIO7 (CE1) | SIGNAL | SPI0 chip enable 1 |
Notes
- Revision 2 layout (pin 3=GPIO2, 5=GPIO3, 13=GPIO27); Rev1 differed on these three.
- Identical to pins 1-26 of the modern 40-pin header.
- 3.3 V logic, not 5 V tolerant.
Reference: Raspberry Pi GPIO documentation (P1 Rev2)· verified 2026-06-27