Raspberry Pi Pinout

BCM 3 (I2C Clock)

Alt0Alt1Alt2Alt3Alt4Alt5
I2C1 SCLSMI SA2DPI HSYNCAVEOUT HSYNCAVEIN HSYNC
  • Physical pin 5
  • BCM pin 3
  • Wiring Pi pin 9
  • BCM pin 1 on Rev 1 ( very early ) Pi

SCL (i2c Clock) is one of the i2c pins on the Pi, learn more about i2c.

SCL includes a fixed, 1.8 kohms pull-up to 3.3v, which means this pin is not suitable for use as a general purpose IO where no pullup resistor is desired.