More than one pcf8574 expander

Tagged: pcf8574

This topic has 11 replies, 1 voice, and was last updated 3 years, 2 months ago by Renzo Mischianti.

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- 11 August 2020 at 16:46 #5522
  hmronline
  Could you please provide an example for initializing a few (let’s say 4) gpio expanders ?
  I was thinking on having an array, in order to be able to do something like this: gpioExpander[3].digitalWrite(7, HIGH);
  
  Is that possible ?
  
  Thanks in advance!
- 11 August 2020 at 16:48 #5523
  Renzo Mischianti
  Keymaster
  Hi hmronline,
  I think something like this can work
```
#include "Arduino.h"
#include "PCF8574.h"

PCF8574 pcf8574_1(0x38);
PCF8574 pcf8574_2(0x39);


PCF8574 arrayOfPCF[2];
//The setup function is called once at startup of the sketch
void setup()
{
	Serial.begin(115200);

	pcf8574_1.pinMode(P0, OUTPUT);
	pcf8574_1.pinMode(P1, OUTPUT);
	pcf8574_1.pinMode(P2, OUTPUT);

	pcf8574_2.pinMode(P1, OUTPUT);
	pcf8574_2.pinMode(P2, OUTPUT);
	pcf8574_2.pinMode(P3, OUTPUT);


	pcf8574_1.begin();
	pcf8574_2.begin();

	arrayOfPCF[0] = pcf8574_1;
	arrayOfPCF[1] = pcf8574_1;

}


void loop()
{
	arrayOfPCF[0].digitalWrite(P1, HIGH);
	arrayOfPCF[1].digitalWrite(P1, HIGH);
	delay(2000);
	arrayOfPCF[0].digitalWrite(P1, HIGH);
	arrayOfPCF[1].digitalWrite(P1, HIGH);
	delay(2000);

}
```
  Give me a feedback.
  Bye Renzo
- 11 August 2020 at 16:49 #5524
  hmronline
  Hi Renzo, thanks for you prompt response!
  
  I’ve tried something similar before, but no luck with that, I’ve got an error on array declaration: no matching function for call to ‘PCF8574::PCF8574()’
  
  Any suggestions ?
- 11 August 2020 at 16:49 #5525
  Renzo Mischianti
  Keymaster
  I try to compile my sketch and no error, can you post your code??
- 11 August 2020 at 16:51 #5526
  hmronline
  I’m using your code, but have to mention I’m testing it with platform.io (using visual studio code).
  The provided error appears after hitting Build task.
  
  Complete error message is:
  
  src/main.cpp:7:21: error: no matching function for call to 'PCF8574::PCF8574()' PCF8574 arrayOfPCF[2]; ^ src/main.cpp:7:21: note: candidates are: In file included from src/main.cpp:2:0: .pio/libdeps/nodemcuv2/PCF8574 library/PCF8574.h:111:2: note: PCF8574::PCF8574(uint8_t, uint8_t, uint8_t, uint8_t, void (*)()) PCF8574(uint8_t address, uint8_t sda, uint8_t scl, uint8_t interruptPin, void (*interruptFunction)()); ^ .pio/libdeps/nodemcuv2/PCF8574 library/PCF8574.h:111:2: note: candidate expects 5 arguments, 0 provided .pio/libdeps/nodemcuv2/PCF8574 library/PCF8574.h:110:2: note: PCF8574::PCF8574(uint8_t, uint8_t, uint8_t) PCF8574(uint8_t address, uint8_t sda, uint8_t scl); ^ .pio/libdeps/nodemcuv2/PCF8574 library/PCF8574.h:110:2: note: candidate expects 3 arguments, 0 provided .pio/libdeps/nodemcuv2/PCF8574 library/PCF8574.h:107:2: note: PCF8574::PCF8574(uint8_t, uint8_t, void (*)()) PCF8574(uint8_t address, uint8_t interruptPin, void (*interruptFunction)() ); ^ .pio/libdeps/nodemcuv2/PCF8574 library/PCF8574.h:107:2: note: candidate expects 3 arguments, 0 provided .pio/libdeps/nodemcuv2/PCF8574 library/PCF8574.h:106:2: note: PCF8574::PCF8574(uint8_t) PCF8574(uint8_t address); ^ .pio/libdeps/nodemcuv2/PCF8574 library/PCF8574.h:106:2: note: candidate expects 1 argument, 0 provided .pio/libdeps/nodemcuv2/PCF8574 library/PCF8574.h:103:7: note: constexpr PCF8574::PCF8574(const PCF8574&) class PCF8574 { ^ .pio/libdeps/nodemcuv2/PCF8574 library/PCF8574.h:103:7: note: candidate expects 1 argument, 0 provided .pio/libdeps/nodemcuv2/PCF8574 library/PCF8574.h:103:7: note: constexpr PCF8574::PCF8574(PCF8574&&) .pio/libdeps/nodemcuv2/PCF8574 library/PCF8574.h:103:7: note: candidate expects 1 argument, 0 provided *** [.pio/build/nodemcuv2/src/main.cpp.o] Error 1
- 11 August 2020 at 16:52 #5527
  hmronline
  Could you add an option to set I2C Address with begin function instead of setting it with class constructor ?
  
  As an example, this library (which seems its abandoned) receives I2C address on begin function: https://github.com/microseti/pcf857x
  
  It seems this way is easier to set an array of PCF8574 instances, something like this:
```
#include "Arduino.h"
#include "PCF8574.h"

PCF8574 arrayOfPCF[2];

//The setup function is called once at startup of the sketch
void setup()
{
Serial.begin(115200);

// This way, I2C addresses could be determined during execution time (maybe obtained with an i2cscanner function).

arrayOfPCF[0].begin(0x38);
arrayOfPCF[1].begin(0x39);

arrayOfPCF[0].pinMode(P0, OUTPUT);
arrayOfPCF[0].pinMode(P1, OUTPUT);
arrayOfPCF[0].pinMode(P2, OUTPUT);

arrayOfPCF[1].pinMode(P1, OUTPUT);
arrayOfPCF[1].pinMode(P2, OUTPUT);
arrayOfPCF[1].pinMode(P3, OUTPUT);

}

void loop()
{
arrayOfPCF[0].digitalWrite(P1, HIGH);
arrayOfPCF[1].digitalWrite(P1, HIGH);
delay(2000);
arrayOfPCF[0].digitalWrite(P1, HIGH);
arrayOfPCF[1].digitalWrite(P1, HIGH);
delay(2000);

}
```
  What do you think ?
- 11 August 2020 at 16:54 #5528
  Renzo Mischianti
  Keymaster
  Hi hmronline,
  It’s true, the sketch not working on Arduino, only in esp8266 core, try this
```
#include "Arduino.h"
#include "PCF8574.h"

PCF8574 pcf8574_1(0x38);
PCF8574 pcf8574_2(0x39);

PCF8574* arrayOfPCF[2];
//The setup function is called once at startup of the sketch
void setup()
{
	Serial.begin(115200);

	pcf8574_1.pinMode(P0, OUTPUT);
	pcf8574_1.pinMode(P1, OUTPUT);
	pcf8574_1.pinMode(P2, OUTPUT);

	pcf8574_2.pinMode(P1, OUTPUT);
	pcf8574_2.pinMode(P2, OUTPUT);
	pcf8574_2.pinMode(P3, OUTPUT);

	pcf8574_1.begin();
	pcf8574_2.begin();

	arrayOfPCF[0] = &pcf8574_1;
	arrayOfPCF[1] = &pcf8574_2;

}

void loop()
{
	arrayOfPCF[0]->digitalWrite(P1, HIGH);
	arrayOfPCF[1]->digitalWrite(P1, HIGH);
	delay(2000);
	arrayOfPCF[0]->digitalWrite(P1, HIGH);
	arrayOfPCF[1]->digitalWrite(P1, HIGH);
	delay(2000);

}
```
  or
```
#include "Arduino.h"
#include "PCF8574.h"

PCF8574 pcf8574_1(0x38);
PCF8574 pcf8574_2(0x39);

PCF8574 arrayOfPCF[2] = {pcf8574_1, pcf8574_2};
//The setup function is called once at startup of the sketch
void setup()
{
	Serial.begin(115200);

	pcf8574_1.pinMode(P0, OUTPUT);
	pcf8574_1.pinMode(P1, OUTPUT);
	pcf8574_1.pinMode(P2, OUTPUT);

	pcf8574_2.pinMode(P1, OUTPUT);
	pcf8574_2.pinMode(P2, OUTPUT);
	pcf8574_2.pinMode(P3, OUTPUT);

	pcf8574_1.begin();
	pcf8574_2.begin();

}

void loop()
{
	arrayOfPCF[0].digitalWrite(P1, HIGH);
	arrayOfPCF[1].digitalWrite(P1, HIGH);
	delay(2000);
	arrayOfPCF[0].digitalWrite(P1, HIGH);
	arrayOfPCF[1].digitalWrite(P1, HIGH);
	delay(2000);

}
```
  Bye Renzo
- 11 August 2020 at 16:54 #5529
  hmronline
  Second option seems its working fine for me, thank you Renzo!
- 9 March 2021 at 08:27 #10489
  sergio contro
  Ciao.
  
  First example , last row before loop function :
  
  arrayOfPCF[1] = &pcf8574_1;
  
  should be
  
  arrayOfPCF[1] = &pcf8574_2;
  - 9 March 2021 at 08:37 #10490
    Renzo Mischianti
    Keymaster
    Hi Sergio,
    Thanks, I fixed It.
    Bye Renzo
- 20 September 2021 at 11:12 #14937
  Chandrasiri
  I need to have two PCF8574s and one of them will use INT . I use them with ESP8266 and wish to define pins for SDA and SCL. So I need to define Address, SDA Pin No, SCL Pin No, Interrupt Pin No, Interrupt Function but pcf8574 constructor can only accept 3 (either ADD, SDA, SCL or ADD, Int Pin, Int Function). Pls help how to do this
- 20 September 2021 at 14:17 #14948
  Renzo Mischianti
  Keymaster
  Hi,
  you can check this to understand the basic constructor.
  
  To manage interrupt you can find all information here at this link.
  
  Bye Renzo
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