Raspberry pi pin guide

Any of the GPIO pins can be designated in software as an input or output pin and used for a wide range of purposes.

Voltages

Two 5V pins and two 3.3V pins are present on the board, as well as a number of ground pins (GND), which can not be reconfigured. The remaining pins are all general-purpose 3.3V pins, meaning outputs are set to 3.3V and inputs are 3.3V-tolerant.

Inputs and outputs:

A GPIO pin designated as an input pin can be read as high (3.3V) or low (0V). This is made easier with the use of internal pull-up or pull-down resistors. Pins GPIO2 and GPIO3 have fixed pull-up resistors, but for other pins this can be configured in software.

A GPIO pin designated as an output pin can be set to high (3.3V) or low (0V).

Other functions on pins:

As well as simple input and output devices, the GPIO pins can be used with a variety of alternative functions, some are available on all pins, others on specific pins.

• PWM (pulse-width modulation)
  • Software PWM available on all pins
  • Hardware PWM available on GPIO12, GPIO13, GPIO18, GPIO19
    
    
• SPI
  
  • SPI0: MOSI (GPIO10); MISO (GPIO9); SCLK (GPIO11); CE0 (GPIO8), CE1 (GPIO7)
  • SPI1: MOSI (GPIO20); MISO (GPIO19); SCLK (GPIO21); CE0 (GPIO18); CE1 (GPIO17); CE2 (GPIO16)
    
    
• I2C
  
  • Data: (GPIO2); Clock (GPIO3)
  • EEPROM Data: (GPIO0); EEPROM Clock (GPIO1)
    
    
• Serial
  
  • TX (GPIO14); RX (GPIO15)
    
    

Other useful information

A GPIO reference can be accessed on your Raspberry Pi by opening a terminal window and running the command pinout. 

If wanting to use the I2C bus then it needs to be enabled in the Raspberry Pi configuration panel.

Each pin can have load of absolute maximum 16 ma, and the total for all GPIO pins must not exceed 50 ma.