If you're following along with a Raspberry Pi, Beaglebone or any other supported small linux computer, we'll use a special library called adafruit_blinka (named after Blinka, the CircuitPython mascot) to provide the layer that translates the CircuitPython hardware API to whatever library the Linux board provides. It's CircuitPython, on Pi!
If you haven't set up Blinka and the Adafruit IO Python Library yet on your Raspberry Pi, follow our guide:
We use two pins on the Pi (SDA/SCL) to communicate over I2c with the PCA9685. You only have to do this step once per Raspberry Pi, the I2C interface is disabled by default.
Once you're done with this and have rebooted, verify you have the SPI devices with the command:
sudo i2cdetect -y 1
The output from running this command should look like the following: