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2.1.9 Joystick

Introduction

In this project, We’re going to learn how joystick works. We manipulate the Joystick and display the results on the screen.

Required Components

In this project, we need the following components.

../_images/image317.png

It’s definitely convenient to buy a whole kit, here’s the link:

Name

ITEMS IN THIS KIT

LINK

Raphael Kit

337

Raphael Kit

You can also buy them separately from the links below.

COMPONENT INTRODUCTION

PURCHASE LINK

GPIO Extension Board

BUY

Breadboard

BUY

Jumper Wires

BUY

Resistor

BUY

Joystick Module

-

ADC0834

-

Schematic Diagram

When the data of joystick is read, there are some differents between axis: data of X and Y axis is analog, which need to use ADC0834 to convert the analog value to digital value. Data of Z axis is digital, so you can directly use the GPIO to read, or you can also use ADC to read.

../_images/image319.png ../_images/image320.png

Experimental Procedures

Step 1: Build the circuit.

../_images/image193.png

Step 2: Go to the folder of the code.

cd ~/raphael-kit/c/2.1.9/

Step 3: Compile the code.

gcc 2.1.9_Joystick.c -lwiringPi

Step 4: Run the executable file.

sudo ./a.out

After the code runs, turn the Joystick, then the corresponding values of x, y, Btn are displayed on screen.

Note

If it does not work after running, or there is an error prompt: "wiringPi.h: No such file or directory", please refer to Install and Check the WiringPi.

Code

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

typedef unsigned char uchar;
typedef unsigned int uint;

#define     ADC_CS    0
#define     ADC_CLK   1
#define     ADC_DIO   2
#define     BtnPin    3

uchar get_ADC_Result(uint channel)
{
    uchar i;
    uchar dat1=0, dat2=0;
    int sel = channel > 1 & 1;
int odd = channel & 1;
    pinMode(ADC_DIO, OUTPUT);
    digitalWrite(ADC_CS, 0);
    // Start bit
    digitalWrite(ADC_CLK,0);
    digitalWrite(ADC_DIO,1);    delayMicroseconds(2);
    digitalWrite(ADC_CLK,1);    delayMicroseconds(2);
//Single End mode
    digitalWrite(ADC_CLK,0);
    digitalWrite(ADC_DIO,1);    delayMicroseconds(2);
    digitalWrite(ADC_CLK,1);    delayMicroseconds(2);
    // ODD
    digitalWrite(ADC_CLK,0);
    digitalWrite(ADC_DIO,odd);  delayMicroseconds(2);
    digitalWrite(ADC_CLK,1);    delayMicroseconds(2);
    //Select
    digitalWrite(ADC_CLK,0);
    digitalWrite(ADC_DIO,sel);    delayMicroseconds(2);
digitalWrite(ADC_CLK,1);
    digitalWrite(ADC_DIO,1);    delayMicroseconds(2);
    digitalWrite(ADC_CLK,0);
    digitalWrite(ADC_DIO,1);    delayMicroseconds(2);
    for(i=0;i<8;i++)
    {
        digitalWrite(ADC_CLK,1);    delayMicroseconds(2);
        digitalWrite(ADC_CLK,0);    delayMicroseconds(2);
        pinMode(ADC_DIO, INPUT);
        dat1=dat1<<1 | digitalRead(ADC_DIO);
    }
    for(i=0;i<8;i++)
    {
        dat2 = dat2 | ((uchar)(digitalRead(ADC_DIO))<<i);
        digitalWrite(ADC_CLK,1);    delayMicroseconds(2);
        digitalWrite(ADC_CLK,0);    delayMicroseconds(2);
    }
    digitalWrite(ADC_CS,1);
    pinMode(ADC_DIO, OUTPUT);
    return(dat1==dat2) ? dat1 : 0;
}
int main(void)
{
    uchar x_val;
    uchar y_val;
    uchar btn_val;
    if(wiringPiSetup() == -1){ //when initialize wiring failed,print messageto screen
        printf("setup wiringPi failed !");
        return 1;
    }
    pinMode(BtnPin,  INPUT);
    pullUpDnControl(BtnPin, PUD_UP);
    pinMode(ADC_CS,  OUTPUT);
    pinMode(ADC_CLK, OUTPUT);

    while(1){
        x_val = get_ADC_Result(0);
        y_val = get_ADC_Result(1);
        btn_val = digitalRead(BtnPin);
        printf("x = %d, y = %d, btn = %d\n", x_val, y_val, btn_val);
        delay(100);
    }
    return 0;
}

Code Explanation

uchar get_ADC_Result(uint channel)
{
    uchar i;
    uchar dat1=0, dat2=0;
    int sel = channel > 1 & 1;
    int odd = channel & 1;
    pinMode(ADC_DIO, OUTPUT);
    digitalWrite(ADC_CS, 0);
    // Start bit
    digitalWrite(ADC_CLK,0);
    digitalWrite(ADC_DIO,1);    delayMicroseconds(2);
    digitalWrite(ADC_CLK,1);    delayMicroseconds(2);
    //Single End mode
    digitalWrite(ADC_CLK,0);
    digitalWrite(ADC_DIO,1);    delayMicroseconds(2);
    digitalWrite(ADC_CLK,1);    delayMicroseconds(2);
    ......

The working process of the function is detailed in 2.1.4 Potentiometer.

while(1){
        x_val = get_ADC_Result(0);
        y_val = get_ADC_Result(1);
        btn_val = digitalRead(BtnPin);
        printf("x = %d, y = %d, btn = %d\n", x_val, y_val, btn_val);
        delay(100);
    }

VRX and VRY of Joystick are connected to CH0, CH1 of ADC0834 respectively. So the function getResult() is called to read the values of CH0 and CH1. Then the read values should be stored in the variables x_val and y_val. In addition, read the value of SW of joystick and store it into the variable Btn_val. Finally, the values of x_val, y_val and Btn_val shall be printed with print() function.

Phenomenon Picture

../_images/image194.jpeg