Interrup expender use pcf8574

 To use the interrupt pin with the PCF8574, which is an 8-bit I/O expander for I2C bus, you can follow these steps:

1. Identify the interrupt pin: The PCF8574 does not have a dedicated interrupt pin. However, it can be configured to generate an interrupt by setting the INT output to an interrupt mode. The INT pin is internally connected to the ORed outputs of all the I/O pins.

2. Connect the INT pin: Connect the INT pin of the PCF8574 to an interrupt-capable pin on your microcontroller or host system. Ensure that you have the necessary pull-up resistor on the INT pin to provide a default high level when no interrupt is occurring.

3. Configure the interrupt: Set up the interrupt handling mechanism in your microcontroller's firmware or software. Configure the interrupt pin as an input and enable the interrupt functionality. Refer to your microcontroller's documentation to learn how to set up interrupts.

4. Enable interrupt mode on the PCF8574: To enable the interrupt functionality on the PCF8574, you need to write to the configuration registers. The specific method for configuring the interrupt mode can vary depending on the library or code you are using. Here's a general example using .

   In this example, we set all the pins of the PCF8574 as inputs (by writing 0xFF to the control register at address 0x02). This configuration allows any change on the I/O pins to trigger an interrupt on the INT pin.

#include <Wire.h>

void setup() {

  Wire.begin();  // Initialize I2C bus

  Wire.beginTransmission(0x20);  // Replace 0x20 with your PCF8574 address

  Wire.write(0x02);  // Control register address

  Wire.write(0xFF);  // Set all bits as inputs

  Wire.endTransmission();

}

void loop() {

  // Your main program code

}

1. Handle the interrupt: When an interrupt occurs on the INT pin, the microcontroller's interrupt service routine (ISR) will be executed. In the ISR, you can read the state of the PCF8574's I/O pins to determine which pin triggered the interrupt and take appropriate actions.

Remember to refer to the datasheet of the PCF8574 and the documentation of your microcontroller for more specific details on configuring interrupts and accessing the I2C bus. The example provided here is a general guideline and may require modifications to suit your specific hardware and software setup.