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GPIO Introduction

Let's take a detailed look at the Walnut Pi's GPIO, i.e., its 40-pin GPIO header (similar to Raspberry Pi). The Walnut Pi is already a great single-board computer, but the GPIO design makes it easier for users to perform various DIY electronic projects, giving you an experience similar to using a powerful microcontroller development board.

gpio

Below is the Walnut Pi GPIO pinout diagram:

  • Walnut Pi 2B pinout

As shown in the table and diagram above, GPIO is similar to traditional microcontroller development. In addition to regular I/O pins, it also features I2C, UART, SPI and other bus interfaces, as well as power output pins (3.3V and 5V). You can connect various sensors and modules, all of which will be covered in the later embedded programming chapters.

Power Pins​

The Walnut Pi GPIO header provides two 5V and two 3.3V output pins, as well as 8 GND pins for external power supply.

General-Purpose I/O​

Except for the power pins, all I/O pins can be configured as input/output pins. The I/O voltage level is 3.3V.

Other Functions​

Some pins have additional functions, as detailed below:

PWM (Pulse Width Modulation)​

PB4, PB6, PI10, PI11, PI12, PI2, PI3, PI4, PI5, PI6, PI7, PI15, PI16, PI13, PI14, PI0, PI1, PL2, PL3, PL4, PL5, PL6 support hardware PWM.

Query command:

gpio pin pwm

gpio

UART​

  • TX2(PB0), RX2(PB1)
  • TX3(PI11), RX3(PI12)
  • TX4(PI0), RX4(PI1)
  • TX5(PI2), RX5(PI3)
  • TX6(PI6), RX6(PI7)
  • TX7(PB13), RX7(PB14)
  • TX8(PL2), RX8(PBL3)

Query command:

gpio pin uart

gpio

I2C​

  • SDA1(PB5), SCL1(PB4)
  • SDA2(PI16), SCL2(PI15)

Query command:

gpio pin i2c

gpio

SPI​

  • SPI1: MOSI (PI4); MISO (PI5); SCLK (PI3); CS0 (PI2), CS1 (PI6)

Query command:

gpio pin spi

gpio