Use Different I2C Pins with ESP32 (change default I2C pins 變更內定I2C的腳位)

Use Different I2C Pins with ESP32 (change default I2C pins)

源自於 https://randomnerdtutorials.com/esp32-i2c-communication-arduino-ide/

With the ESP32 you can set almost any pin to have I2C capabilities, you just need to set that in your code.

When using the ESP32 with the Arduino IDE, use the Wire.h library to communicate with devices using I2C. With this library, you initialize the I2C as follows:

Wire.begin(I2C_SDA, I2C_SCL);

So, you just need to set your desired SDA and SCL GPIOs on the I2C_SDA and I2C_SCL variables.

However, if you’re using libraries to communicate with those sensors, this might not work and it might be a bit tricky to select other pins. That happens because those libraries might overwrite your pins if you don’t pass your own Wire instance when initializing the library.

In those cases, you need to take a closer look at the .cpp library files and see how to pass your own TwoWire parameters.

For example, if you take a closer look at the Adafruit BME280 library, you’ll find out that you can pass your own TwoWire to the begin() method.

So, the example sketch to read from the BME280 using other pins, for example GPIO 33 as SDA and and GPIO 32 as SCL is as follows.

/*
  Rui Santos
  Complete project details at https://RandomNerdTutorials.com/esp32-i2c-communication-arduino-ide/
  
  Permission is hereby granted, free of charge, to any person obtaining a copy
  of this software and associated documentation files.
  
  The above copyright notice and this permission notice shall be included in all
  copies or substantial portions of the Software.
*/

#include <Wire.h>
#include <Adafruit_Sensor.h>
#include <Adafruit_BME280.h>

#define I2C_SDA 33
#define I2C_SCL 32

#define SEALEVELPRESSURE_HPA (1013.25)

TwoWire I2CBME = TwoWire(0);
Adafruit_BME280 bme;

unsigned long delayTime;

void setup() {
  Serial.begin(115200);
  Serial.println(F("BME280 test"));
  I2CBME.begin(I2C_SDA, I2C_SCL, 100000);

  bool status;

  // default settings
  // (you can also pass in a Wire library object like &Wire2)
  status = bme.begin(0x76, &I2CBME);  
  if (!status) {
    Serial.println("Could not find a valid BME280 sensor, check wiring!");
    while (1);
  }

  Serial.println("-- Default Test --");
  delayTime = 1000;

  Serial.println();
}

void loop() { 
  printValues();
  delay(delayTime);
}

void printValues() {
  Serial.print("Temperature = ");
  Serial.print(bme.readTemperature());
  Serial.println(" *C");
  
  // Convert temperature to Fahrenheit
  /*Serial.print("Temperature = ");
  Serial.print(1.8 * bme.readTemperature() + 32);
  Serial.println(" *F");*/
  
  Serial.print("Pressure = ");
  Serial.print(bme.readPressure() / 100.0F);
  Serial.println(" hPa");

  Serial.print("Approx. Altitude = ");
  Serial.print(bme.readAltitude(SEALEVELPRESSURE_HPA));
  Serial.println(" m");

  Serial.print("Humidity = ");
  Serial.print(bme.readHumidity());
  Serial.println(" %");

  Serial.println();
}

View raw code

Click image to enlarge

Let’s take a look at the relevant parts to use other I2C pins.

First, define your new I2C pins on the I2C_SDA and I2C_SCL variables. In this case, we’re using GPIO 33 and GPIO 32.

#define I2C_SDA 33
#define I2C_SCL 32

Create a new TwoWire instance. In this case, it’s called I2CBME. This simply creates an I2C bus.

TwoWire I2CBME = TwoWire(0);

In the setup(), initialize the I2C communication with the pins you’ve defined earlier. The third parameter is the clock frequency.

I2CBME.begin(I2C_SDA, I2C_SCL, 400000);

Finally, initialize a BME280 object with your sensor address and your TwoWire object.

status = bme.begin(0x76, &I2CBME);

After this, you can use use the usual methods on your bme object to request temperature, humidity and pressure.

Note: if the library you’re using uses a statement like wire.begin() in its file, you may need to comment that line, so that you can use your own pins.