A Feather board without ambition is a Feather board without FeatherWings! This is the 8-Channel PWM or Servo​ FeatherWing, you can add 8 x 12-bit PWM outputs to your Feather board. Using our Feather Stacking Headers or Feather Female Headers you can connect a FeatherWing on top or bottom of your Feather board and let the board take flight!

You want to make a cool robot, maybe a hexapod walker, or maybe just a piece of art with a lot of moving parts. Or maybe you want to drive a lot of LEDs with precise PWM output. What now? You could give up OR you could just get our handy PWM and Servo FeatherWing. It's a lot like our popular PWM/Servo Shield but with half the channels & squished into a nice small portable size and works with any of our Feather boards.

Since the FeatherWing only uses the I2C (SDA & SCL pins), it works with any and all Feathers- ATmega32u4, ATSAM M0 or ESP8266-based. You can stack it with any other FeatherWing or with itself (just make sure you have each wing with a unique I2C address) Check out our range of Feather boards here.

Specs:

• There's an I2C-controlled PWM driver with a built in clock. That means that, unlike the TLC5940 family, you do not need to continuously send it signal tying up your microcontroller, its completely free running!
• It is 5V compliant, which means you can control it from a 3.3V Feather and still safely drive up to 6V outputs (this is good for when you want to control white or blue LEDs with 3.4+ forward voltages)
• 6 address select pins so you can stack up to 62 of these on a single i2c bus, a total of 496 outputs - that's a lot of servos or LEDs
• Adjustable frequency PWM up to about 1.6 KHz
• 12-bit resolution for each output - for servos, that means about 4us resolution at 60Hz update rate
• Configurable push-pull or open-drain output

We wrapped up this lovely chip into a FeatherWing with a couple nice extras:

• Terminal block for power input (or you can use the 0.1" breakouts on the side)
• Reverse polarity protection on the terminal block input
• Green power-good LED
• Two groups of 4 outputs on either side, 8 total.
• Stackable design. You'll need to pick up stacking headers and right angle 3x4 headers in order to stack on top of this shield without the servo connections getting in the way.
• A spot to place a big capacitor on the V+ line (in case you need it)
• 220 ohm series resistors on all the output lines to protect them, and to make driving LEDs trivial
• Solder jumpers for the 6 address select pins

This product comes with a fully tested and assembled wing as well as 2 pieces of 3x4 male straight header (for servo/LED plugs), a 2-pin terminal block (for power) and a stick of 0.1" header so you can plug into a Feather. A little light soldering will be required to assemble and customize the board by attaching the desired headers but it is a 15 minute task that even a beginner can do.

If you want to use right-angle 3x4 headers, we also carry a 4 pack in the shop. Servos and Feather not included, but we have lots of servos in the shop.

Power Pins

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:

• 5v 2A switching power supply (up to perhaps 4 servos)
• 5v 10A switching power supply (up to perhaps 16 servos)
• 4xAA Battery Holder - 6v with Alkaline cells. 4.8v with NiMH rechargeable cells, portable!
• 4.8 or 6v Rechargeable RC battery packs from a hobby store.

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

I2C Data Pins

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

Servo / PWM Pins

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:

1. GND - power and signal ground
2. V+ - 5V power from the terminal block for powering servos or LEDs that are common anode or require 5V
3. 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.

It's easy to control PWM or servos with the Adafruit 8-Channel PWM or Servo FeatherWing. There are multiple CircuitPython libraries available to work with the different features of this board including Adafruit CircuitPython PCA9685, and Adafruit CircuitPython ServoKit. These libraries make it easy to write Python code to control PWM and servo motors.

CircuitPython Microcontroller Wiring

First assemble the FeatherWing exactly as shown in the previous pages. There's no wiring needed to connect the FeatherWing to the Feather. The example below shows the FeatherWing attached to a Feather using the stacking assembly method, and wiring a barrel jack to the power terminal to attach an appropriate external power source to the FeatherWing. The FeatherWing will not power servos without an external power source!

To dim an LED, wire it to the board as follows. Note: you don't need to use a resistor to limit current through the LED as the FeatherWing will limit the current to around 10mA.

To control a servo, wire it to the board as follows.

CircuitPython Installation of ServoKit and Necessary Libraries

You'll need to install a few libraries on your Feather board.

First make sure you are running the latest version of Adafruit CircuitPython for your board.

Next you'll need to install the necessary libraries to use the hardware--carefully follow the steps to find and install these libraries from Adafruit's CircuitPython library bundle.  Our CircuitPython starter guide has a great page on how to install the library bundle.

If you choose, you can manually install the libraries individually on your board:

• adafruit_pca9685
• adafruit_bus_device
• adafruit_register
• adafruit_motor
• adafruit_servokit

Before continuing make sure your board's lib folder or root filesystem has the adafruit_pca9685.mpy, adafruit_register, adafruit_motor, adafruit_bus_device and adafruit_servokit files and folders copied over.

Next connect to the board's serial REPL so you are at the CircuitPython >>> prompt.

CircuitPython Usage

To demonstrate the usage, we'll use Python code to control PWM to dim an LED and to control servo motors from the board's Python REPL.

Dimming LEDs

This FeatherWing uses the PCA9685. Each channel of the FeatherWing can be used to control the brightness of an LED.  The PCA9685 generates a high-speed PWM signal which turns the LED on and off very quickly.  If the LED is turned on longer than turned off it will appear brighter to your eyes.

First you'll need to import the necessary modules, initialize the I2C bus for your board, and create an instance of the class.

import board
import busio
import adafruit_pca9685
i2c = busio.I2C(board.SCL, board.SDA)
wing = adafruit_pca9685.PCA9685(i2c)

import board
import busio
import adafruit_pca9685
i2c = busio.I2C(board.SCL, board.SDA)
wing = adafruit_pca9685.PCA9685(i2c)

The PCA9685 class provides control of the PWM frequency and each channel's duty cycle.  Check out the PCA9685 class documentation for more details.

For dimming LEDs you typically don't need to use a fast PWM signal frequency and can set the board's PWM frequency to 60hz by setting the frequency attribute:

wing.frequency = 60

wing.frequency = 60

The FeatherWing supports 8 separate channels that share a frequency but can have independent duty cycles. That way you could dim 8 LEDs separately!

The PCA9685 object has a channels attribute which has an object for each channel that can control the duty cycle. To get the individual channel use the [] to index into channels.

led_channel = wing.channels[0]

led_channel = wing.channels[0]

Now control the LED brightness by controlling the duty cycle of the channel connected to the LED. The duty cycle value should be a 16-bit value, i.e. 0 to 0xffff (65535), which represents what percent of the time the signal is on vs. off.  A value of 0xffff is 100% brightness, 0 is 0% brightness, and in-between values go from 0% to 100% brightness.

For example set the LED completely on with a duty_cycle of 0xffff:

led_channel.duty_cycle = 0xffff

led_channel.duty_cycle = 0xffff

After running the command above you should see the LED light up at full brightness!

Now turn the LED off with a duty_cycle of 0:

led_channel.duty_cycle = 0

led_channel.duty_cycle = 0

Try an in-between value like 1000:

led_channel.duty_cycle = 1000

led_channel.duty_cycle = 1000

You should see the LED dimly lit.  Try experimenting with other duty cycle values to see how the LED changes brightness!

For example make the LED glow on and off by setting duty_cycle in a loop:

# Increase brightness:
for i in range(0xffff):
    led_channel.duty_cycle = i

# Decrease brightness:
for i in range(0xffff, 0, -1):
    led_channel.duty_cycle = i

# Increase brightness:
for i in range(0xffff):
    led_channel.duty_cycle = i

# Decrease brightness:
for i in range(0xffff, 0, -1):
    led_channel.duty_cycle = i

These for loops take a while because 16-bits is a lot of numbers. CTRL-C to stop the loop from running and return to the REPL.

That's all there is to dimming LEDs using CircuitPython and the PWM/Servo FeatherWing!

Controlling Servos

We've written a handy CircuitPython library for the various PWM/Servo kits called Adafruit CircuitPython ServoKit that handles all the complicated setup for you. All you need to do is import the appropriate class from the library, and then all the features of that class are available for use. We're going to show you how to import the ServoKit class and use it to control servo motors with the Adafruit PWM/Servo FeatherWing.

First you'll need to import and initialize the ServoKit class. You must specify the number of channels available on your board. The FeatherWing has 8 channels, so when you create the class object, you will specify 8.

from adafruit_servokit import ServoKit
kit = ServoKit(channels=8)

from adafruit_servokit import ServoKit
kit = ServoKit(channels=8)

Now you're ready to control both standard and continuous rotation servos.

Standard Servos

To control a standard servo, you need to specify the channel the servo is connected to. You can then control movement by setting angle to the number of degrees.

For example to move the servo connected to channel 0 to 180 degrees:

kit.servo[0].angle = 180

kit.servo[0].angle = 180

To return the servo to 0 degrees:

kit.servo[0].angle = 0

kit.servo[0].angle = 0

With a standard servo, you specify the position as an angle. The angle will always be between 0 and the actuation range. The default is 180 degrees but your servo may have a smaller sweep. You can change the total angle by setting actuation_range.

For example, to set the actuation range to 160 degrees:

kit.servo[0].actuation_range = 160

kit.servo[0].actuation_range = 160

Often the range an individual servo recognises varies a bit from other servos. If the servo didn't sweep the full expected range, then try adjusting the minimum and maximum pulse widths using set_pulse_width_range(min_pulse, max_pulse).

To set the pulse width range to a minimum of 1000 and a maximum of 2000:

kit.servo[0].set_pulse_width_range(1000, 2000)

kit.servo[0].set_pulse_width_range(1000, 2000)

That's all there is to controlling standard servos with the PWM/Servo FeatherWing, CircuitPython and ServoKit!

Continuous Rotation Servos

To control a continuous rotation servo, you must specify the channel the servo is on. Then you can control movement using throttle.

For example, to start the continuous rotation servo connected to channel 1 to full throttle forwards:

kit.continuous_servo[1].throttle = 1

kit.continuous_servo[1].throttle = 1

To start the continuous rotation servo connected to channel 1 to full reverse throttle:

kit.continuous_servo[1].throttle = -1

kit.continuous_servo[1].throttle = -1

To set half throttle, use a decimal:

kit.continuous_servo[1].throttle = 0.5

kit.continuous_servo[1].throttle = 0.5

And, to stop continuous rotation servo movement set throttle to 0:

kit.continuous_servo[1].throttle = 0

kit.continuous_servo[1].throttle = 0

That's all there is to controlling continuous rotation servos with the PWM/Servo FeatherWing, CircuitPython and ServoKit!

Full Example Code

# SPDX-FileCopyrightText: 2021 ladyada for Adafruit Industries
# SPDX-License-Identifier: MIT

"""Simple test for a standard servo on channel 0 and a continuous rotation servo on channel 1."""

import time

from adafruit_servokit import ServoKit

# Set channels to the number of servo channels on your kit.
# 8 for FeatherWing, 16 for Shield/HAT/Bonnet.
kit = ServoKit(channels=8)

kit.servo[0].angle = 180
kit.continuous_servo[1].throttle = 1
time.sleep(1)
kit.continuous_servo[1].throttle = -1
time.sleep(1)
kit.servo[0].angle = 0
kit.continuous_servo[1].throttle = 0

# SPDX-FileCopyrightText: 2021 ladyada for Adafruit Industries
# SPDX-License-Identifier: MIT

"""Simple test for a standard servo on channel 0 and a continuous rotation servo on channel 1."""

import time

from adafruit_servokit import ServoKit

# Set channels to the number of servo channels on your kit.
# 8 for FeatherWing, 16 for Shield/HAT/Bonnet.
kit = ServoKit(channels=8)

kit.servo[0].angle = 180
kit.continuous_servo[1].throttle = 1
time.sleep(1)
kit.continuous_servo[1].throttle = -1
time.sleep(1)
kit.servo[0].angle = 0
kit.continuous_servo[1].throttle = 0

Adding a Capacitor to the thru-hole capacitor slot

We have a spot on the PCB for soldering in an electrolytic capacitor. Based on your usage, you may or may not need a capacitor. If you are driving a lot of servos from a power supply that dips a lot when the servos move, n * 100uF where n is the number of servos is a good place to start - eg 470uF or more for 5 servos. Since its so dependent on servo current draw, the torque on each motor, and what power supply, there is no "one magic capacitor value" we can suggest which is why we don't include a capacitor in the kit.

Adding/Stacking Servo Feathers - Using different i2c addresses

If you need more Servos, you can stack the FeatherWings (see Stacking Assembly) - each new Wing will give you 8 more Servos

You'll need to solder in stacking Feather headers so you can plug more Wings on top!

You'll also need to use right-angle 3x4 headers on the Servo Wings so that the servos connect off the ends rather than straight up

Each I2C device connected to your Feather must be assigned a unique address. This is done with the address jumpers on the bottom of the board. The I2C base address for each board is 0x40. The binary address that you program with the address jumpers is added to the base I2C address.

To program the address offset, use a drop of solder to bridge the corresponding address jumper for each binary '1' in the address.

Board 0: Address = 0x40 Offset = binary 00000 (no jumpers required)
Board 1: Address = 0x41 Offset = binary 00001 (bridge A0)
Board 2: Address = 0x42 Offset = binary 00010 (bridge A1)
Board 3: Address = 0x43 Offset = binary 00011 (bridge A0 & A1)
Board 4: Address = 0x44 Offset = binary 00100 (bridge A2)
etc.

See how we do this for the Arduino Shield vesion of this board, its nearly identical:

Files

• PCA9685 Datasheet
• EagleCad PCB files on GitHub
• Fritzing object in Adafruit Fritzing library

Schematic

Click to embiggen

Fabrication Print

Dimensions in Inches