Hardware Reference
In-Depth Information
PIN NUMBER
PURPOSE
23
GPIO 11 (SCLK)
24
GPIO 8 (CE0)
25
Ground
26
GPIO 7 (CE1)
The pins are meant for input no higher than 3.3 V, and there is no overvoltage
protection.
Inter-Integrated Circuit (I2C)
The I2C interface (SDA and SCL), which you can access through pins 3 and 5, is a
connection for low-speed peripherals or sensors. You can have multiple devices con-
nected through the same pins.
Pulse-Width Modulation (PWM)
Pin 12 offers control for motors similar to analog control through pulse-width modu-
lation (labeled PCM_CLK). For some purposes, you can achieve the same effect
through software, which may be useful since the Pi has only one PWM pin.
Universal Asynchronous Receiver/Transmitter (UART)
The UART pins (14/TXD and 15/RXD) are used for serial console access. If you don't
need that, you can switch them to GPIO for an extra two GPIO pins. This is also true
of the I2C and SPI pins, but you're least likely to want to use the UART pins.
Serial Peripheral Interface Bus (SPI)
The SPI pins are the pins you'll use for some types of sensors or attaching other de-
vices. SPI operates in master/slave fashion:
• 19 - Master Out, Slave In (MOSI)
• 21 - Master In, Slave Out (MISO)
• 23 - Serial Clock (SCLK)
• 24 - CE0 (chip select)
• 26 - CE1 (chip select)
