How to use wiringPi?

Intro

This document introduces the basic usage and API of wiringpi with examples.
Wiringpi is a package made to control gpio 40pin with C in Raspberry Pi.

[picture 1] gpio header

Usage

install wiringPi

After boot Raspberry, Install package (git code)

$ git clone https://github.com/WiringPi/WiringPi.git
$ cd WiringPi
$ ./build

Version Check

$ gpio -v

GPIO readall

$ gpio readall

 +-----+-----+---------+------+---+---Pi 4b--+---+------+---------+-----+-----+
 | BCM | wPi |   Name  | Mode | V | Physical | V | Mode |  Name   | wPi | BCM |
 +-----+-----+---------+------+---+----++----+---+------+---------+-----+-----+
 |     |     |    3.3V |      |   |  1 || 2  |   |      | 5V      |     |     |
 |   2 |   8 |   SDA.1 |   IN | 1 |  3 || 4  |   |      | 5V      |     |     |
 |   3 |   9 |   SCL.1 |   IN | 1 |  5 || 6  |   |      | 0V      |     |     |
 |   4 |   7 |  GPIO.7 |   IN | 1 |  7 || 8  | 1 | IN   | TxD     | 15  | 14  |
 |     |     |      0V |      |   |  9 || 10 | 1 | IN   | RxD     | 16  | 15  |
 |  17 |   0 |  GPIO.0 |   IN | 0 | 11 || 12 | 0 | IN   | GPIO.1  | 1   | 18  |
 |  27 |   2 |  GPIO.2 |   IN | 0 | 13 || 14 |   |      | 0V      |     |     |
 |  22 |   3 |  GPIO.3 |   IN | 0 | 15 || 16 | 0 | IN   | GPIO.4  | 4   | 23  |
 |     |     |    3.3V |      |   | 17 || 18 | 0 | IN   | GPIO.5  | 5   | 24  |
 |  10 |  12 |    MOSI |   IN | 0 | 19 || 20 |   |      | 0V      |     |     |
 |   9 |  13 |    MISO |   IN | 0 | 21 || 22 | 0 | IN   | GPIO.6  | 6   | 25  |
 |  11 |  14 |    SLCK |   IN | 0 | 23 || 24 | 1 | IN   | CE0     | 10  | 8   |
 |     |     |      0V |      |   | 25 || 26 | 1 | IN   | CE1     | 11  | 7   |
 |   0 |  30 |   SDA.0 |   IN | 1 | 27 || 28 | 1 | IN   | SCL.0   | 31  | 1   |
 |   5 |  21 | GPIO.21 |   IN | 1 | 29 || 30 |   |      | 0V      |     |     |
 |   6 |  22 | GPIO.22 |   IN | 1 | 31 || 32 | 0 | IN   | GPIO.26 | 26  | 12  |
 |  13 |  23 | GPIO.23 |   IN | 0 | 33 || 34 |   |      | 0V      |     |     |
 |  19 |  24 | GPIO.24 |   IN | 0 | 35 || 36 | 0 | IN   | GPIO.27 | 27  | 16  |
 |  26 |  25 | GPIO.25 |   IN | 0 | 37 || 38 | 0 | IN   | GPIO.28 | 28  | 20  |
 |     |     |      0V |      |   | 39 || 40 | 0 | IN   | GPIO.29 | 29  | 21  |
 +-----+-----+---------+------+---+----++----+---+------+---------+-----+-----+
 | BCM | wPi |   Name  | Mode | V | Physical | V | Mode |  Name   | wPi | BCM |
 +-----+-----+---------+------+---+---Pi 4b--+---+------+---------+-----+-----+

compile

option 1

$ gcc -o main main.c -lwiringPi

option 2

$ gcc -o main main.c -lwiringPi -lwiringPiDev -lm -lpthread -lrt -lcrypt

API

wiringpi supports a number of APIs.
I only cover some of the most commonly used functions.

Mode	function
map	physPinToGpio
map	wpiPinToGpio
ADC	analogRead
ADC	analogWrite
GPIO	digitalRead
GPIO	digitalWrite
GPIO	pinMode
I2C	wiringPiI2CRead
I2C	wiringPiI2CSetup
I2C	wiringPiI2CWrite
PWM	pwmSetClock
PWM	pwmSetMode
PWM	pwmSetRange
PWM	pwmWrite
SPI	wiringPiSPIDataRW
SPI	wiringPiSPIGetFd
SPI	wiringPiSPISetMode
SPI	wiringPiSPISetup
…	…

Bold text will be covered in detail in the wiringPi code part.

test code

This is test code.
Connect wpi pin 0 and 1. (phys pin #11 and #12)

#include <wiringPi.h>
#include <stdio.h>

#define PINR 0
#define PINW 1

int main()
{
    wiringPiSetup();
    pinMode(PINR, INPUT);
    pinMode(PINW, OUTPUT);

    while (1) {
      digitalWrite(PINR, HIGH);
      printf("pin %d status: %d\n", PINR, digitalRead(PINR));
      delay(500);
      digitalWrite(PINW, LOW);
      printf("pin %d status: %d\n", PINR, digitalRead(PINR));
      delay(500);
    }
}