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Voltages
Two 5V pins and two 3V3 pins are present on the board, as well as a number of ground pins (0V), which are unconfigurable.
The remaining pins are all general purpose 3V3 pins, meaning outputs are set to 3V3 and inputs are 3V3-tolerant.
Outputs
A GPIO pin designated as an output pin can be set to high (3V3) or low (0V).
Inputs
A GPIO pin designated as an input pin can be read as high (3V3) 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.
More
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