How to choose alternate I2C pins on ESP32?

Question

I'm a begginer with Arduino and this may be a basic question but I'm facing an issue.

I'm using a HTU21D sensor with an ESP32. This sensor use I2C communication. Inside the Arduino library, there is this function to start to collect data:

//Start I2C communication
void HTU21D::begin(TwoWire &wirePort)
{
 _i2cPort = &wirePort; //Grab which port the user wants us to use
 _i2cPort->begin();
}

As you can see, we can set in this function which port we want to use. Perfect. But my probleme is that I don't know how to use the type TwoWire. I checked some documentation but I was still unable to find a solution. I want to use GPIO_16 as SDA and GPIO_17 as SCL. So I tried something like that without result: htu21d.begin(Wire(16, 17));

How to set SDA and SCL pin in TwoWire type ? (in my case GPIO_16 and GPIO_17)

• Juraj: did you try htu21d.begin(Wire);? Wire is an object, an instance of TwoWire class. it is defined in Wire.h at the end
• Gazouu: But how do I tell Wire that I want to use pin 16 as SDA and pin 17 as SCL ?
• jsotola: found this void TwoWire::begin(int sdaPin, int sclPin, uint32_t frequency) here github.com/espressif/arduino-esp32/blob/master/libraries/Wire/…
• Juraj: you call Wire.begin

Answer 1

I was able to resolve my issue thanks to Juraj comment. I did :

Wire.begin(16, 17);
htu21d.begin(Wire);

• alireza: worked for me too, thanks, Wire.begin(SDA, SCK); for ssd1306 library for oled .
• Georgi Peev: Some of the ESP32 pins do not support SPI. You can only use pins 11,12,13,18,23,24,25,26,29 and 30 as SDA or SCK.

Answer 2

Here is the example of how you can change esp8266 i2c pins. I used it for my ESP8266 and bme280, but the same for Arduino and other sensors.

#include <Wire.h>
#include <Adafruit_Sensor.h>
#include <Adafruit_BME280.h>
void setup() {
 Wire.pins(12,2); //new SDA SCL pins (D6 and D4 for esp8266)
 Serial.begin(115200);
 delay(100);
 bme.begin(0x76, &Wire); //here is the address for my bme280 and instance of TwoWire object
} 

For my ESP8266 I tried to use GPIO0 for SDA and GPIO2 for SCL, but no luck. Probably because GPIO0 is a Flash pin. Changing SDA to GPIO12 (or D6 pin) helped me.