I would to declare an array of multiple PCF8575 devices within a struct, something like:

PCF8575 PCF[DEVICES];

Then, in another part of my code do something like:

PCF[0].digitalRead(PINNUM);

I cannot figure out how to do this with this library as it appears at minimum I need to assign an address with the constructor.

Any suggestions would be greatly appreciated.

Thanks.

Hi,

From datasheet, I only figured out if I want to set a pin (e.g P17) to output LOW, I can use I2C to write 3 bytes as the following:
0100 A2A1A00
0xxx xxxx
xxxx xxxx

Is it correct? But I cannot figure out how to set P17 to output mode.

I am trying to add a PCF8575 (well actually a PCF8574) to an esp32cam . But should be the same...
(note I am a little new at this...)

I am trying to map to different pins for the SDA and SCL - since the esp32cam SDA and SCL pins are not avaialbe. But I believe I should be able to map them to most any pin.
But can't make it work.

I wanted to change pins for the SDA and SCL on an esp32.
I wanted to use pins 27 and 14 for an esp32 for testing (but really I wanted this for an esp32cam using pins 12 and 2).

I tried using the wire.h library and the PCF8574 lib...but for some reason it keep son forcing pins 21 and 22 as the SDA and SCL...and I did read that I need to sort out the .cpp files to make sure it is not being forced to set SDL and SCL pins... on this tutorial https://randomnerdtutorials.com/esp32-i2c-communication-arduino-ide/ but I have no clue how to do that!!

And I see on a different sensor - the libraries will allow you to change pins...with the twowires...

"In those cases, you need to take a closer look at the .cpp library files and see how to pass your own TwoWire parameters." https://randomnerdtutorials.com/esp32-i2c-communication-arduino-ide/ . But I cannot figure out how to do this...

For testing I was using the code below.

using I2C scanner I get address for PCF as 0x38
running below sketch - SDA and SCL are still using pins 21 and 22 ...and it works - the LED blinks on/off using pins 21 and 22...

But pins should be mapped to 27 and 14....
How to fix??
Can you update library to allow mapping?? Or am I doing something wrong?
Thanks!

#include "Wire.h"
#include "Arduino.h"
#include "PCF8574.h"

TwoWire I2Cone = TwoWire(0);

PCF8574 pcf8574(&I2Cone, 0x38);

(note your tutorial it think it has typo... line 39 >> PCF8574 pcf8574(&I2Ctwo, 0x20); >>> I think it should be PCF8574 pcf8574(&2Ctwo, 0x20); ) Your editor is added letters...

void setup(){

Serial.begin(115200);
delay (100);

I2Cone.begin(27,14,100000);

// Set the pinModes
pcf8574.pinMode(P0, OUTPUT);
pcf8574.pinMode(P1, OUTPUT);
pcf8574.begin();
}

void loop(){
pcf8574.digitalWrite(P0, HIGH);
pcf8574.digitalWrite(P1, LOW);
delay(1000);
pcf8574.digitalWrite(P0, LOW);
pcf8574.digitalWrite(P1, HIGH);
delay(1000);
}

Hi,
I tried the keypress on a switch button and followed the wiring on your home page.
I then used the code here https://github.com/xreef/PCF8575_library/blob/master/examples/keyPressedPin1/keyPressedPin1.ino
I am using an ESP32 and it actually does not work for me.

If I removed the 10K pull-down resistor connected to the ground then it now work.
I brought out my tester and I noticed that when the switch is open the reading at the P1 pin is around 4.2V (HIGH) but when I pressed the button it goes down to 3.9V which still registers as a HIGH which is not registering a LOW.

I tried removing the 10K resistor and everything is ok?

Can you comment on this or if the wiring is correct? Or I could be missing some setup on my end. Thank you.

I have the digitalread on all pins working on my esp32, I followed the example but is not working. When I measure the pin to ground it stays low on digitalwrite.

This is the expansion board I am using

I have solderd vcc to vdd (for not using the voltage regulator)

In the library I did

#define NOT_SEQUENTIAL_PINOUT

#include <PCF8575.h>
#include <Wire.h>

TwoWire I2Cone = TwoWire(0);
//TwoWire I2Ctwo = TwoWire(1);
PCF8575 PCF(&I2Cone, 0x20, 16,17);

void setup() {
	Serial.begin(115200);
	while (!Serial);
	//PCF.pinMode(P00, INPUT);

	I2Cone.begin(16, 17, 400000); // SDA pin 16, SCL pin 17, 400kHz frequency

	for (int i = 0; i < 8; i++) {
		PCF.pinMode(i, OUTPUT);
	}
	
	//PCF.begin(16, 17);

	PCF.begin();

	write();
}
void loop() {
	delay(1000);
	//read();
}
void read() {
	Serial.print("val: ");
	Serial.println(PCF.digitalRead(P00));
}
void write() {
	//PCF.digitalWrite(P07, HIGH);

	for (int i = 0; i < 8; i++) {
		PCF.digitalWrite(i, HIGH);
	}
}

Hi, great libray, thank you!

PCF8575.h define device pins as P0 - P15, see lines 68 - 83 contain:

#define P0  	0
#define P1  	1
#define P2  	2
#define P3  	3
#define P4  	4
#define P5  	5
#define P6  	6
#define P7  	7
#define P8  	8
#define P9  	9
#define P10  	10
#define P11  	11
#define P12  	12
#define P13  	13
#define P14  	14
#define P15  	15

but in real world PCF8575 device pins are labeled P00 - P07 and then P10 - P17, would you consider changing the code to:

#define P00  	0
#define P01  	1
#define P02  	2
#define P03  	3
#define P04  	4
#define P05  	5
#define P06  	6
#define P07  	7
#define P10  	8
#define P11  	9
#define P12  	10
#define P13  	11
#define P14  	12
#define P15  	13
#define P16  	14
#define P17  	15

so P0 -> P00, P1 -> P01 .. P7 -> P07, then there is no P8 and P9, insted 8th pin is P10, 9th pin is P11, etc...

not sure if you'd want to commit to this change. Posting this in hopes someone will find this usefull as it may be confusing...

I have ESP32 and 2 PCF8575 like inputs + 2 PCF8575 like outputs on standart 21-22 SDA SSL.

`//Все GPIO могут быть настроены для обработки прерываний.
#define ESP32_INTERRUPTED_PIN1 2
#define ESP32_INTERRUPTED_PIN2 3

//адреса расширителей
#define addrIn1 0x20
#define addrIn2 0x21
#define addrOut1 0x22
#define addrOut2 0x23

// Function interrupt
void keyChangedOnPCF1();
void keyChangedOnPCF2();

bool keyChanged1 = false;
bool keyChanged2 = false;

PCF8575 in1(addrIn1, ESP32_INTERRUPTED_PIN1, keyChangedOnPCF1);
PCF8575 in2(addrIn2, ESP32_INTERRUPTED_PIN2, keyChangedOnPCF2);
PCF8575 out1(addrOut1);
PCF8575 out2(addrOut2);

//uint32_t click_st, dbl_st, hold_st; // переменные для текуших статусов входных сигналов

struct Button {
const uint8_t PIN;
bool pressed;
bool dbl;
bool hold;
};

unsigned long timeElapsed;

byte mac[] = {
0x00, 0xAA, 0xBB, 0xCC, 0xDE, 0x02
};

void setup() {
Serial.begin(112560);

// Set pinMode to OUTPUT
for (uint8_t i = 0; i < 16; i++) {
in1.pinMode(i, INPUT);
in2.pinMode(i, INPUT);
out1.pinMode(i, INPUT);
out2.pinMode(i, INPUT);
}
//in1.begin(); //
//in2.begin();
//out1.begin();
//out2.begin();`

I need using *.begin 4 times or no need begin for esp32 and 21-22 SDA-SCL?

how to use music throught pcf8575 ?

Any chance you can do the same fix you did here xreef/PCF8574_library#15 to the PCF8575 library ?
This would allow setting the pin state on .begin().

Currently I hacked the .cpp file on line 179 as follows:
uint16_t usedPin = readMode; //writeMode |
And this works (as per datasheet 0 on a write call sets the pin low) but have not fully tested it.

Hi there, your forum is apparently not accepting registrations... Is it still active?

Hi.
Why doesn't it work?
Am I making a mistake somewhere?

void loop()
{
pcf8575.digitalWrite(P10, HIGH);
int p10Digital = pcf8575.digitalRead(P10);
Serial.println(p10Digital);
PCF8575::DigitalInput di = pcf8575.digitalReadAll();
Serial.print(di.p10);
Serial.print(" - ");
Serial.print(di.p11);
Serial.print(" - ");
Serial.print(di.p12);
Serial.print(" - ");
Serial.println(di.p13);
delay(5000);
//---------------------------------------------------
pcf8575.digitalWrite(P10, LOW);
int p10Digital1 = pcf8575.digitalRead(P10);
Serial.println(p10Digital1);
PCF8575::DigitalInput di1 = pcf8575.digitalReadAll();
Serial.print(di1.p10);
Serial.print(" - ");
Serial.print(di1.p11);
Serial.print(" - ");
Serial.print(di1.p12);
Serial.print(" - ");
Serial.println(di1.p13);
delay(5000);
}

ser.monitor
1
0 - 0 - 0 - 0
0
0 - 0 - 0 - 0
1
0 - 0 - 0 - 0
0
0 - 0 - 0 - 0
1
0 - 0 - 0 - 0
0
0 - 0 - 0 - 0
1
0 - 0 - 0 - 0
0
0 - 0 - 0 - 0
1

They need to write the status P10 - P17 via the ser.monitor 00000000

My code

PCF8575 pcf8575(0x20);

long in =0;
void setup() {

// put your setup code here, to run once:

pcf8575.pinMode(P0, OUTPUT);
pcf8575.begin();

pcf8575.digitalWrite(P0, HIGH);
in = millis();

}
void loop() {

if(Serial.available())
{
int valA = Serial.parseInt();
Serial.println(valA);

if( valA == 2){
pcf8575.digitalWrite(P0, HIGH);

}

Serial.flush();
}

if(millis() - in >= 1000){

// put your main code here, to run repeatedly:

uint8_t val =  pcf8575.digitalRead(P0);
if( val == LOW) {
  Serial.print("P0: ");
  Serial.print( "LOW");
 Serial.println();
 }

in = millis();

}
}

Although I write pcf8575.digitalWrite(P0, HIGH), it always prints LOW.

Hi,
First of all, thanks for all your hard work on this and the PCF8574. That one I use all the time with no problems. Recently, I tried to do the same things with the PCF8575. All the ports work as expected as OUTPUT like this:

void setup(){
    Wire.begin(SDA_GPIO, SCL_GPIO);

    for (size_t i = 0; i < 16; i++)
        pcf.pinMode(i, OUTPUT);

    for (size_t i = 0; i < 16; i++)
        pcf.digitalWrite(i, HIGH);

    pcf.begin();
}

void loop(){
    if (millis() - i2cMillis > 250)
    {
        for (size_t i = 0; i < 16; i++)
            pcf.digitalWrite(i, 1 - pcf.digitalRead(i));

        i2cMillis = millis();
    }
}

Awesome! But when I try to use the ports as input they fail miserably:

void setup(){
    Wire.begin(SDA_GPIO, SCL_GPIO);

    for (size_t i = 0; i < 16; i++)
        pcf.pinMode(i, INPUT);

    pcf.begin();
}

void loop(){
    PCF8575::DigitalInput di = pcf.digitalReadAll();
    SerialMon.printf("%u - %u - %u - %u - %u - %u - %u - %u\r\n", di.p0, di.p1, di.p2, di.p3, di.p4, di.p5, di.p6, di.p7);
}

resulting in this:

0 - 0 - 0 - 0 - 0 - 0 - 0 - 0

Looking at the circuit with an oscilloscope I can see that although all the pins are pulled up to 3.3V with a 10k resistor, the PCF8575 pulls them down constantly to Gnd.

I have already spent 2 days on trying to figure out what went wrong, but I'm stuck. Any idea what I'm missing?

Thanks for any pointers!

ps: my environment is Windows 11 64 bit, VS Code with PlatformIO. and this is the relevant bit of platformio.ini:

##################################################
#   ENVIRONMENT
##################################################

[env:esp32s3]
board = esp32-s3-devkitc-1

platform = espressif32
framework = arduino

##################################################
#   PRE-BUILD
##################################################
extra_scripts = 
    pre:../../scripts/preIncrementBuildNumber.py
    platformio_upload.py

##################################################
#   BUILD
##################################################

build_type = release

board_build.filesystem = littlefs

lib_deps =
    ; xreef/PCF8574 library @ ^2.3.6    
    xreef/PCF8575 library @ ^1.1.1


##################################################
#   UPLOAD
##################################################

upload_protocol = esptool
upload_port = COM5
upload_speed = 921600