Using the PCF8591 on the Pioneer600 with the Raspberry Pi

The Raspberry Pi doesn’t support any Analog to digital or digital to analog capabilities by default, so if you want to use analog sensors on Raspberry Pi, you will need some sort of  external AD expansion board is required.

A popular chip is the PCF8591, lets have a quick look at this chip

I used a Pioneer600 board which has one of these chips on it among other features

Parts

The Pioneer600 costs around $39 for many useful features

Name Link
Raspberry Pi
Pioneer600 Raspberry Pi Expansion Board Pioneer600

DAC

C program based on BCM library

#include <bcm2835.h>
#include <stdio.h>
#include <unistd.h>

int main(int argc, char **argv)
{
    char Buf[]={0, 0};
    unsigned char value=0;

    if (!bcm2835_init()) return 1;
    bcm2835_i2c_begin();
    // The I2C address of PCF8591 is 0x48.
    bcm2835_i2c_setSlaveAddress(0x48);
    bcm2835_i2c_set_baudrate(10000);
    printf("start..........\n");

    while(1)
    {
        Buf[0] = 0x40;
        Buf[1] = value++;
        bcm2835_i2c_write(Buf, 2);
        printf("AOUT: %d\n", value);

        bcm2835_delay(20);
    }

    bcm2835_i2c_end();
    bcm2835_close();
    return 0;
}

Save the file as “pcf8591.c”. Compile and run with:

gcc -Wall pcf8591.c -o pcf8591 -lbcm2835
sudo ./pcf8591

Python example using smbus

#!/usr/bin/python
import smbus
import time

address = 0x48
cmd = 0x40
value = 0

bus = smbus.SMBus(1)
while True:
    bus.write_byte_data(address,cmd,value)
    value += 1
    if value == 256:
        value =0
    print("AOUT:%3d" %value)
    time.sleep(0.01)

Save the file as “pcf8591.py” and execute it with:

sudo python pcf8591.py

C example using WiringPi

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

#define Address 0x48
#define BASE 64
#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);

    while(1)
    {
        analogWrite(A0,value);
        printf("AOUT: %d\n",value++);
        delay(20);
    }
}

Save the file as “pcf8591.c”. Compile and run with:

gcc -Wall pcf8591.c -o pcf8591 -lbcm2835 -lwiringPi
sudo ./pcf8591

ADC

C example using the  BCM library

#include <bcm2835.h>
#include <stdio.h>
#include <unistd.h>

int main(int argc, char **argv)
{
    char Buf[]={0};
    unsigned char i;

    if (!bcm2835_init())return 1;
    bcm2835_i2c_begin();
    bcm2835_i2c_setSlaveAddress(0x48);
    bcm2835_i2c_set_baudrate(10000);
    printf("start..........\n");

    while(1)
    {
        for(i = 0;i < 4;i++)
        {
            Buf[0] = i;
            bcm2835_i2c_write_read_rs(Buf,1,Buf,1);
            bcm2835_i2c_read (Buf,1);
            printf("AIN%d:%5.2f  ",i,(double)Buf[0]*3.3/255);
        }
        printf("\n");
        bcm2835_delay(100);
    }

    bcm2835_i2c_end();
    bcm2835_close();
    return 0;
}

Save the file as “pcf8591.c”. Compile and run with:

gcc -Wall pcf8591.c -o pcf8591 -lbcm2835
sudo ./pcf8591

Python example

#!/usr/bin/python
import smbus
import time

address = 0x48
A0 = 0x40
A1 = 0x41
A2 = 0x42
A3 = 0x43
bus = smbus.SMBus(1)
while True:
    bus.write_byte(address,A0)
    value = bus.read_byte(address)
    print("AOUT:%1.3f  " %(value*3.3/255))
    time.sleep(0.1)

Save the file as “pcf8591.py” and execute it with:

sudo python pcf8591.py

C example using  WiringPi

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

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

int main(void)
{
    int value;
    wiringPiSetup();
    pcf8591Setup(BASE,Address);

    while(1)
    {
        value = analogRead(A0);
        printf("Analoge: %dmv\n",value*3300/255);
        delay(1000);
    }
}

Save the file as “pcf8591.c”. Compile and run with:

gcc -Wall pcf8591.c -o pcf8591 -lbcm2835 -lwiringPi
sudo ./pcf8591
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