For PlatformIO users: The setters setSDA() and setSCL() are not available in Wire class.

Instead you can do (e.g. for I2C0):

#define I2C_SDA_PIN 20
#define I2C_SCL_PIN 21
MbedI2C myWire(I2C_SDA_PIN,I2C_SCL_PIN);
Adafruit_SSD1306 display(SCREEN_WIDTH, SCREEN_HEIGHT, &myWire, OLED_RESET);

and at the beginning of setup() before display.begin(…):

myWire.begin();

Thanks for sharing.
Regards,
Sara

Adafruit_SSD1306 display(SCREEN_WIDTH, SCREEN_HEIGHT, &Wire1, -1);

Now, you need to add 3 lines to your setup() section before you call the display.begin routine

For I2C0
Wire.setSDA(16); // Change the 16 to the GPIO pin you’re using
Wire.setSCL(17); // Change the 17 to the GPIO pin you’re using
Wire.begin();

For I2C1
Wire1.setSDA(26); // Change the 26 to the GPIO pin you’re using
Wire1.setSCL(27); // Change the 27 to the GPIO pin you’re using
Wire1.begin();

That got it to work for me. I wasn’t able to find this info anywhere and basically stumbled onto it by accident.

Hi.
You can use other combination of pins, but you need to choose certain combinations.
See this section about I2C in our pinout guide: https://randomnerdtutorials.com/raspberry-pi-pico-w-pinout-gpios/#i2c

After choosing the pins:

In the setup(), you need to start an I2C communication using GPIO x and GPIO y. So, you need to add the following line:

Wire.begin(x, y);

After that, initialize the display with the following parameters:

if(!display.begin(SSD1306_SWITCHCAPVCC, 0x3C, false, false)) {
The parameters set as false ensure that the library doesn’t use the default I2C pins and use the pins defined in the code.

I think this should work but I haven’t tested it.

Regards,
Sara

Hi.
What do you mean?
Regards,
Sara

is it possible to change the default I2C adress of the pico?

thank you

Great.
I’m glad everything is working as expected.
Regards,
Sara

Thank you for your response. I did the entire installation procedure again. When installing the boards I was immediately given an update option. After doing this, all programs worked as before and the error messages disappeared.
I have no idea what went wrong before, but it works again./
Thank you for your patience.

Weird….
I’m not sure what might be causing the issue.
You said it worked before… I really don’t know what might have caused the issue…

Regards,
Sara