# KS0213 Keyestudio RPI GPIO-PCF8591 Shield

![](media/image-20260113120826896.png)

## 1. Introduction

There's no AD/DA function on the Raspberry Pi GPIO interface, this may trouble you in the Pi development. However, it won't be a problem anymore. The RPI GPIO-PCF8591 Shield allows you to add high-precision AD/DA functions to the Raspberry Pi.

The PCF8591 features four-8-bit analog to digital converters and a single 8-bit digital to analog converter. This will operate through the I2C interface on the Raspberry Pi.

## 2. Connection Diagram

Plug it directly into Raspberry Pi to start your works as shown in below figure.

![](media/image-20260113120956383.png)

## 3. Sample Code

DA(Digital to Analog) Source Code：

```c
#include <wiringPi.h>
#include <pcf8591.h>
#include <stdio.h>

#define Address 0x48
#define BASE 64          //DA Output
#define A0 BASE+0
#define A1 BASE+1
#define A2 BASE+2
#define A3 BASE+3

int main(void)
{
    unsigned char value;
	wiringPiSetup();
	pcf8591Setup(BASE,Address);    //configuration pcf8591	
	while(1)
	{		
               analogWrite(BASE,value);      //write the value output on AOUT interface
               printf("AOUT:%d\n",value);     //print that value
               delay(50);	
	}
}
```

AD(Analog to Digital) Source Code: 

```c
#include <wiringPi.h>
#include <pcf8591.h>
#include <stdio.h>

#define Address 0x48         //pcf8591 address 
#define BASE 64
#define A0 BASE+0           //A0 input
#define A1 BASE+1           //A1 input
#define A2 BASE+2           //A2 input
#define A3 BASE+3           //A3 input
int main(void)
{
    unsigned char value;
	wiringPiSetup();
	pcf8591Setup(BASE,Address);        //configurationpcf8591
	
	while(1)
	{
               value=analogRead(A0);     // read A0 value          
               printf("A0:%d\n",value);  // print A0 value
               delay(100);	
	}
}
```

## 4. Program Writing

Download  Resources :  [Resources](./Resources.7z)

**1.Install Wiringpi Library**

Wiring Pi is a library. WiringPi supports analog reading and writing, and while there is no native analog hardware on a Pi by default, modules are provided so other A/D and D/A devices can be implemented relatively easily.

(it should open in a new page) to download the latest version. This will download a .tar file with a name like wiringPi-b0a60c3.tar. Then copy the file and put it into the raspberry pi file as shown in below figure:

![](media/image-20260113121406218.png)

Type in this command to unzip the source code and install:

- **tar xfz wiringPi-98bcb20.tar.gz**
- **cd wiringPi-98bcb20**
- **./build**

Note that the actual file name will be different (may not be 98bcb20) – you will have to check the name and adjust accordingly.

Here is the interface after installing WiringPi as shown in below figure.

![](media/image-20260113121506702.png)

WirtingPi includes a set of gpio commands to control the GPIO pins of the Raspberry Pi. Type in the command to check the installation:

- **gpio -v**
- **gpio readall**

The interface as shown in below figure means complete installation.

![](media/image-20260113121530026.png)

**2.Enable I2C Utility**

The I2C bus allows multiple devices to be connected to your Raspberry Pi. Before using I2C it needs to be configured.

Run this command: **sudo raspi-config** and follow the prompts to install I2C. Now complete the following steps:

- Select “9 Advanced Options”
- Select “A6 I2C”

The screen will ask if you want the ARM I2C interface to be enabled :

- Select “Yes”
- Select “Ok”
- Select “Finish” to return to the command line

When you next reboot the I2C module will be loaded.

**3.Programming**

Copy the file pcf8591 provided by us and put it into your pi directory through winSCP. Next, type this command: **cd pcf8591** to go inside the pcf8591 folder. Then type this command: **make** to make an executable file. This means this is the file we run to launch the program.

Finally type this: **sudo ./TTP229** to launch the program.

## 5. Result

DA source code makes AOUT interface output 0-5V voltage; the pi will prints digital value among 0-255 on the terminal after reading out voltage set by AD source code.