This shield has two power supplies. One is logic level power - that is the 3.3V power from the Feather, it is used to power the PWM chip and determines the I2C logic level and the PWM signal logic level.
To power servos you will need to also connect the 5V Servo power supply - this is the power supply for the servos. (If you are lighting up single LEDs you may not need this power supply.) This power supply should be 5 to 6VDC. You can connect this power through the blue terminal block. There is reverse-polarity protection in case you hook up power backwards.
When the servo power pin is powered, the 5VOK LED will be lit. If this LED is not lit, the V+ pins will not have any voltage on them and the servos won't be powered.
Nearly all servos are designed to run on about 5 or 6v. Keep in mind that a lot of servos moving at the same time (particularly large powerful ones) will need a lot of current. Even micro servos will draw several hundred mA when moving. Some high-torque servos will draw more than 1A each under load.
Good power choices are:
You can add an extra large-value electrolytic capacitor to the servo power supply to help stabilize the power supply, see the Usage page for details
The PWM driver does all of the data transfer over the I2C pins, highlighed above SDA and SCL. No other pins are required. There are two 10K pullups to 3V on each.
These pins can be shared with other I2C devices.
The default I2C address is 0x40 and can be changed by closing jumpers on the bottom. See the Advanced Usage page for more details
OK now we get to the fun part. These are the pins we can use for driving LEDs or Servos. There are 8 outputs, each in a 3-pin "port"
Each port contains three pins:
- GND - power and signal ground
- V+ - 5V power from the terminal block for powering servos or LEDs that are common anode or require 5V
- Signal - 3.3V logic signal from the PCA9685 PWM generator
If you're driving LEDs you can probably get away with just using either GND or V+ and the signal. For servos you will need all three pins.