// Embedded SBC Connectors

Raspberry Pi HAT 40-Pin GPIO

Raspberry Pi 40-pin GPIO header (2×20) is the expansion interface for HAT (Hardware Attached on Top) add-on boards, providing SPI, I2C, UART, PWM, and GPIO signals plus 3.3V and 5V power.

// Specifications

Standard

Raspberry Pi HAT specification

Pitch

2.54mm

Pin Count

40 (2x20)

Signals

GPIO SPI I2C UART PWM I2S

Voltage

3.3V logic 5V power

Use Case

HAT boards sensors motor drivers displays

// Pin Reference Table

Pin	Name	Function	Type
1	3V3	3.3V power	PWR
2	5V	5V power	PWR
3	GPIO2	SDA1 I2C data	BUS
4	5V	5V power	PWR
5	GPIO3	SCL1 I2C clock	BUS
6	GND	Ground	GND
7	GPIO4	GPCLK0 clock output	I/O
8	GPIO14	UART TXD transmit	BUS
9	GND	Ground	GND
10	GPIO15	UART RXD receive	BUS
11	GPIO17	General purpose I/O	I/O
12	GPIO18	PCM_CLK PWM	I/O
13	GPIO27	General purpose I/O	I/O
14	GND	Ground	GND
15	GPIO22	General purpose I/O	I/O
16	GPIO23	General purpose I/O	I/O
17	3V3	3.3V power	PWR
18	GPIO24	General purpose I/O	I/O
19	GPIO10	SPI0 MOSI	BUS
20	GND	Ground	GND
21	GPIO9	SPI0 MISO	BUS
22	GPIO25	General purpose I/O	I/O
23	GPIO11	SPI0 CLK	BUS
24	GPIO8	SPI0 CE0 chip select	BUS
25	GND	Ground	GND
26	GPIO7	SPI0 CE1 chip select	BUS
27	ID_SD	HAT ID EEPROM SDA	BUS
28	ID_SC	HAT ID EEPROM SCL	BUS
29	GPIO5	General purpose I/O	I/O
30	GND	Ground	GND
31	GPIO6	General purpose I/O	I/O
32	GPIO12	PWM0	I/O
33	GPIO13	PWM1	I/O
34	GND	Ground	GND
35	GPIO19	SPI1 MISO PCM_FS	BUS
36	GPIO16	SPI1 CE0	BUS
37	GPIO26	General purpose I/O	I/O
38	GPIO20	SPI1 MOSI PCM_DIN	BUS
39	GND	Ground	GND
40	GPIO21	SPI1 CLK PCM_DOUT	BUS