Pololu Maestro Servo Controller¶
MPF supports servos connected to Pololu Maestro servo controllers. Each Maestro can control multiple servos, with models that control 6, 12, 18, or 24 servos.
1. Install the Pololu Maestro drivers¶
Just like any hardware device you connect to a computer, you need to install the drivers so your computer can see it. It is easier to do the initial hardware configuration on a Windows PC. Follow the “Getting Started” section of the Pololu Maestro Servo Controller User’s Guide. You will need to set Maestro’s serial mode to USB Dual Port on the Serial Settings tab of the Maestro Control Center.
2. Configure your hardware platform section¶
Next, you need to tell MPF that you want to use the
for servos. (MPF supports several different models of servo controllers.)
To do this, add
servo_controllers: pololu_maestro to the
of your machine-wide config file, like this:
hardware: platform: fast driverboards: fast servo_controllers: pololu_maestro
This tells MPF that you want the default servo platform to be
If you happen to be using multiple different types of servo controllers, you can
override the default by adding a
platform: entry to individual servo devices
(just like any device in MPF that can have its platform overwritten in the device
3. Configure the serial port¶
Next, you need to tell MPF what port the Maestro is connected to. (Note that when you plug in the Maestro, you’ll see two serial ports appear. You want to use the first one (the lower number).
Add a section to your machine-wide config like this:
pololu_maestro: port: COM5
On Linux or Mac, it will probably look like this:
pololu_maestro: port: /dev/ttyACM0
4. Add your servo devices¶
Now that all your hardware is configured, you can add the actual servos to your
machine config. In MPF, servos are just like any other device (light, LEDs,
coils, etc.) You add a
servos: section to your config, and then create sub
entries in there for each servo you have.
servos: servo1: servo_min: 0.2 servo_max: 0.8 positions: 0.1: servo1_down 0.9: servo1_up reset_position: 0.5 reset_events: reset_servo1 speed_limit: 0.5 acceleration_limit: 0.5 number: 1 servo2: positions: 0.2: servo2_left 1.0: servo2_home reset_position: 1.0 reset_events: reset_servo2 number: 2
Okay, there’s a lot going on in there. Let’s break it down.
First, all these config options are explained in-depth in the servos: section of the config file reference. But let’s point out a few Maestro-specific things here.
number: of the servo is simply which channel on the Maestro board each
servo is connected to. These numbers start with 0, so a Micro Maestro 6 supports
six servos via numbers 0-5, the Mini Maestro 12 supports twelve servos numbered
All servo positioning in MPF is controlled via a floating point value from 0.0 to 1.0. In other words, if you tell a servo to go to position 0.0, that will be one end of its motion, and position 1.0 will be the other end. A value of 0.4 will tell the servo to move to a position that’s 40% along from the start limit to the stop limit, etc.
So that’s universal, 0.0 - 1.0, throughout MPF.
The way servos actually move to a position is that the servo controller sends a series of microsecond-level pulses which the servo reads and can then translate into a certain position. The actual value of these pulses varies depending on the servo controller and servos you actually have.
You may also set servo_min and servo_max if the servo is trying to move beyond its (hardware) limits when setting it to position 0.0 or 1.0. Those two values will be applied to all positions. For instance, if you move it to 0.0 it will actually move to servo_min (0.2 in the example) and to servo_max for 1.0 (0.8 in the example). Everything in between will be interpolated.
The Pololu Maestro servo controllers can accept speed and acceleration settings
which specify how fast the servo moves to the new position, and how (or whether)
it accelerates and decelerates when starting and stopping. If you want to use these
acceleration_limit: settings to your config.
5. Using the servo in your game¶
position: setting contains a list of numerical servo values
mapped to MPF events. So to move a servo in your game, just add the position
you want to the list and then post that event.
Again, see the servos: section of the config file reference for details.
6. Future enhancements¶
Multiple Pololu Maestro controllers can be chained together (via a single USB port). We don’t have support for that yet. (It requires adding and additional address setting to the servo config.) If you want that, let us know and we’ll add it.