I need to use the ID_SD and ID_SC pins for a ultrasonic sensor. Is this possible?

I am already using SDA and SCL for i2c communication so disabling the i2c bus in raspi-config is not an option.

This stackexchange post sheds some light on it but seems to suggest it might be possible. Does anyone have any input on this? Thank you.

1 Answer 1


As far as I am aware you will be fine provided

  1. You are not using a HAT which is configured via ID_SD and ID_SC.
  2. You are not using a Pi3 or if you are using a Pi3 you will not be using the ID_SD or ID_SC GPIO in I2C mode.

The Pi3 uses I2C bus 0 for internal purposes. Setting the ID_SD and ID_SC GPIO as I2C will confuse I2C bus 0.

  • Pins 27/28 are configured as Input after boot. I have seen instructions for setting them as I²C (but have not tested this). They are certainly NOT configured as I²C in normal use, so I see no evidence they cannot be used as normal.
    – Milliways
    Commented Sep 12, 2016 at 11:48
  • @joan I am using it with a Pi 3. Looks like I'm out of luck.
    – Shoumik
    Commented Sep 12, 2016 at 12:01
  • @Milliways I think they're set as i2c if the i2c bus is enabled in raspi-config.
    – Shoumik
    Commented Sep 12, 2016 at 12:03
  • @joan Is it possible to switch my SDA and SCL to ID_SD and ID_SC respectively and use them as my i2c connections? Or is i2c bus 0 for Pi3 absolutely out of the question?
    – Shoumik
    Commented Sep 12, 2016 at 12:44
  • @kimuohs Not on a Pi3. Using I2C bus 0 is a no no. However perhaps Milliways is correct, in which case just try using 27/28 as normal GPIO and see if the sonar ranger works.
    – joan
    Commented Sep 12, 2016 at 13:20

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