RPI3-I2C0-dat.md

Raspberry Pi 3 — ID_SD / ID_SC for I²C?

✔ Yes, they are an I²C bus

• ID_SD = I2C data
  
• ID_SC = I2C clock
  
• This bus is known as I2C bus 0 (I2C0).

⚠ Important limitations

1. Reserved for HAT identification

   • On official Raspberry Pi boards, I2C0 on ID_SD/ID_SC is used exclusively to read the HAT EEPROM.
   • The OS may lock or restrict this bus.

2. 3.3V only

   • Same voltage rules as other Pi GPIO pins.

3. Limited functionality

   • SDA/SCL pull-ups are weak (1.8–3.3 kΩ typical on HATs).
   • Designed for short traces and tiny EEPROMs, not general sensors.

✔ How to enable as general I²C (optional)

Not recommended, but possible.

Edit /boot/config.txt: dtparam=i2c_vc=on

Then you can access it as:

• /dev/i2c-0 (I2C0)

✔ Recommended method

Use the main I²C bus:

• SDA = GPIO 2
  
• SCL = GPIO 3
  
• Bus = /dev/i2c-1

This is the standard I²C bus for all sensors, modules, etc.

ref

• RPI3-dat