Raspberry PI can interact with external world by a number of PINs available on all RPI boards. Raspberry PI Zero pinout shows their arrangement and functions
In this article I’m going to explain Raspberry PI Zero pinout schema, also valid for other currently available RPI models. This is useful when we plan to interface RPI with external world. A simple example is Controlling a stepper motor with Raspberry Pi Zero W.
What Are Raspberry Pi GPIO
GPIO (General Purpose Input/Output) are phisical pins which you can use to acquire states or information from external devices. GPIO can also control external devices.
From electrical point of view, each Raspberry PI has a number of PINS connected to groud (0V) and a number of pins connected to 5V power supply. You can configure all other pins both to receive or provide a tension value which can be 0V (low) or 3,3 V (high). You can manage these settings via Python programs, C/C++, Scratch or Processing3.
With Python, it is also possible to map in your terminal the pinout configuration by using GPIOZero libary. Raspberry PI OS Desktop already includes this library. In Raspberry PI OS Lite you must install it by typing, from terminal:
sudo apt install python3-gpiozero
Once this library is available, use the command
pinout
to have a graphical map. For more info, please refer to Raspberrypi GPIO Documentation.
However, during wiring preparation it is useful to see pins map.
40-pin Schema
Following schema shows classic Raspberry PI Zero pinout schema:
Ground and power pin labels identify their voltage reference. 3V3 and 5V provide different voltage (3,3 Volt and 5 Volt). You will use one voltage or the other based on your external devices specs.
External labels (from GPIO2 to GPIO27) refer to Broadcom (BCM) naming convention. This is the most used one when programming with Python libraries.
Internal labels (from 1 to 40) refer to Board naming convention. This is used with some programming libraries when BCM is not supported or when managing numbers results more confortable.
Some pins can be both used as common ones, but they are capable also for special uses.
I2C can be used to communicate with devices compatible with Inter-Integrated Circuit (a low speed two wire serial protocol). This communicaton standard requires muster-slave roles between the two parts. I2C has two connections: SDA and SCL. They work by sending data to and from the SDA connection, with the speed controlled via the SCL pin.
SPI (Serial Peripheral Interface) is another protocol for RPI with devices in master-slave communication. You can use it for short distances communications. Data is synchronised using a clock (SCLK at GPIO11) from the master (RPi) and the data is sent from the Pi to our SPI component using the MOSI (Master Out Slave In) pin. If the component needs to reply to our Pi, then it will send data back using the MISO (Master In Slave Out) pin.
Commonly known as “Serial,” the UART (Universal Asynchronous Receiver / Transmitter) pins provide a console / terminal login for alternative headless setup. TX and RX stands for transmission and reception.
Difference with WH
Consider that Raspberry Pi Zero and Zero W have an unpopulated pin area. This means that you must solder pins element (usually inside Pi Zero kit or sold alone). Raspberry Pi Zero WH, on the other hand, has GPIO pins already present like all other models.
Enjoy!
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