5.1.2. GPIO Control

Your OpenMV Cam has between 9 (OpenMV Cam M4) to 10 (OpenMV Cam M7) general purpose I/O pins onboard for talking to the real-world. We’re probably going to keep the pin count this low moving into the future to keep the OpenMV Cam tiny.

Anyway, there are a few ways to use GPIO pins.

5.1.2.1. As an Input

To use a GPIO pin as an input just do:

import pyb

p = pyb.Pin("P0", pyb.Pin.IN)
p.value() # Returns 0 or 1.

The pyb.Pin() constructor creates a pin object which you will use to control the I/O pin on your OpenMV Cam. The string you pass to the OpenMV Cam should be P and then 0-8 for the OpenMV Cam M4 and 0-9 for the OpenMV Cam M7.

Once you’ve created the GPIO pin use the pyb.Pin.value() method to get the state of the IO pin.

Finally, if you need to pull-up or pull-down the IO pin pass pyb.Pin.PULL_UP or pyb.Pin.PULL_DOWN as additional arguments to pyb.Pin() constructor:

p = pyb.Pin("P0", pyb.Pin.IN, pyb.Pin.PULL_UP)

5.1.2.2. As an Output

Now, to use a GPIO pin as an output just do:

import pyb

p = pyb.Pin("P0", pyb.Pin.OUT_PP)
p.high() # or p.value(1) to make the pin high (3.3V)
p.low() # or p.value(0) to make the pin low (0V)

It’s that easy! However, what if you want to open-drain an output? Just do:

p = pyb.Pin("P0", pyb.Pin.OUT_OD)

And now pyb.Pin.high() will cause the pin to float while pyb.Pin.low() will pull the pin low. If you need a pull-up resistor on the Pin just add:

p = pyb.Pin("P0", pyb.Pin.OUT_OD, pyb.Pin.PULL_UP)

... to the constructor.