How to use PCF875 module with WEMOS MINI D1

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 The PCF875 is a 16-bit I/O expander that can be controlled via the I2C protocol. The Wemos D1 mini is a development board based on the ESP8266 WiFi module, which also has support for I2C communication.

To use the PCF875 with the Wemos D1 mini, you will need to connect the two devices together using the I2C interface. Here's how you can do it:

  1. Connect the VCC pin of the PCF875 to the 3.3V pin of the Wemos D1 mini.
  2. Connect the GND pin of the PCF875 to the GND pin of the Wemos D1 mini.
  3. Connect the SDA pin of the PCF875 to the D2 pin of the Wemos D1 mini.
  4. Connect the SCL pin of the PCF875 to the D1 pin of the Wemos D1 mini.

Once you have made the necessary connections, you can use a library like the "Wire.h" library in the Arduino IDE to communicate with the PCF875. Here's an example code to get you started:

C++
#include <Wire.h>


#define PCF875_ADDRESS 0x20 // Replace with the address of your PCF875 
void setup() { 
 Wire.begin(); 
 Wire.beginTransmission(PCF875_ADDRESS); 
 Wire.write(0xFF); // Set all pins to input 
 Wire.endTransmission();
 } 
void loop() { 
// Read the value of the PCF875 inputs 
 Wire.beginTransmission(PCF875_ADDRESS); 
 Wire.write(0x00); // Address of input register 
 Wire.endTransmission(); 
 Wire.requestFrom(PCF875_ADDRESS, 1); 
 byte input = Wire.read();

  // Do something with the input value

  if (input & 0x01) { 
// Pin 0 is high 
 } 
if (input & 0x02) { 
// Pin 1 is high

  }
  // ... and so on
}

This code sets all pins of the PCF875 to input mode and then reads the value of the input register in a loop. You can modify it to suit your needs by setting the pins to output mode or writing values to the output register instead.

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