Tutorial step 6: Add keyboard control

Once you get to this point, you should be able to run the MPF game engine as well as the media controller, and you should have a pop-up window which shows some text. You should have your flippers configured, and if you have a physical machine connected, you should be able to flip.

In this step, we’re going to add some keyboard settings to your machine config which will let you map keyboard keys on your computer to switches in your pinball machine. This lets you “play” your game on your computer, which is useful for (1) cases where you don’t have a physical machine nearby, and (2) scenarios where your pinball machine is all the way on the other side of the room and you don’t feel like getting up every time you start MPF.

1. Create your key-to-switch mappings

The first step is to create your key-to-switch mappings in your config file. You do this by adding a keyboard: section, and then in there you add entries for each keyboard key and what type of action in MPF you want to map them to. (Switches, in this case.)

Here’s an example where we map the left flipper button to the Z key and the right flipper button to the ? key:

keyboard:
    z:
        switch: s_left_flipper
    "?":
        switch: s_right_flipper

Note that the question mark is in quotes since it’s a non-standard character, and if you don’t put it in quotes, it will confuse the YAML parser.

Also it’s weird that the key is the question mark, because if you push that key normally it types a slash. (The question mark is the shift option for that key.) So if you set a key mapping and it doesn’t work, try the other character on the key.)

Again make sure that you have proper YAML formatting. The z: and "?": entries should indented the same number of spaces, and the “switch” words should be indented further. Also make sure you have a space to the right of the colon after switch:. At first you might think it’s a bit tedious to have to write the word “switch” for each line. After all, why can’t you just enter them as z: s_left_flipper? This is because the MPF keyboard interface can actually be used to control a lot more than just keys. The details of that are not important now, so for now just make sure your keyboard: section looks like the example above.

2. Test your new keyboard interface

At this point we’re ready to test this out. Pretty simple. Save your config file and run your game again. (Seriously, we can’t tell you how many times things don’t work only to realize we didn’t save our config after changing it!). So now run your game, starting both the media controller and the MPF core. Again you can either do this by running both commands manually in separate windows or by running mpf both.

Note that if you have a physical machine connected, your physical flippers will not flip with the keyboard keys.

Let’s repeat this to be clear. If MPF is connected to physical hardware, pushing flipper button keys on your keyboard will not actually operate your physical switches. (We’ll cover why not in Step 3 below.)

In order for the keys to work, the catch is that the graphical popup window (the one with the attract mode slide in it) has to be the active window for it to receive the keys. (It has to have “focus”, in OS parlance.) Just like how your typing is only sent to the current active window on your desktop, the media controller’s graphical window has to be active for your game to see your keystrokes and convert them to switches. So make sure this window is active (you can ALT+TAB to it or click on it).

Then try hitting the “Z” and “/” keys, and you should see them show up in your console window which is running the MPF game engine as MPF switch events, like this:

INFO : SwitchController : <<<<< switch: s_left_flipper, State:1 >>>>>
INFO : SwitchController : <<<<< switch: s_left_flipper, State:0 >>>>>
INFO : SwitchController : <<<<< switch: s_right_flipper, State:1 >>>>>
INFO : SwitchController : <<<<< switch: s_right_flipper, State:0 >>>>>

When you hit a key that you’ve configured on your keyboard, it’s actually received by the media controller which in turn converts it to switch name and sends it to the MPF game engine. (This is because the MC controls the popup window, not MPF, and you need a window to track key states.)

Notice that there are actually state changes each time you hit and release a key. The “State: 1” means that switch has become active (i.e. when you press down the key), and the “State: 0” means that switch has just become inactive (when you release the key). You can experiment with this by holding down a key and seeing the log event for the associated switch becoming active, and then when you release it you’ll see that switch becoming inactive. Go ahead and play around with this, and notice that you can push and hold the two keys in different orders and combinations.

3. Why can’t you “flip” your physical machine with the keyboard?

If you’re working with a physical machine with this tutorial, you might be surprised to see that your flippers don’t fire when you hit the Z or / keys! Even more confounding is that you will still see the flipper switch events in your console log, and if you reach over and hit the physical buttons on your machine, the flippers will work. So what gives?!?

This happens because MPF uses “hardware rules” to program quick-response mechanisms (like flippers), meaning the flippers are activated by the control system rather than MPF software.

Read the How MPF handles “quick response” mechs (flippers, slingshots, etc.) guide for details.

What if it doesn’t work?

If you don’t see your switch events in the console when you press your keys, there are a few things you can try to troubleshoot:

  • Double-check to make sure you actually saved your updated config file. :)
  • Make sure no modifier keys (shift, control, etc.) are being pressed at the same time. Since there are way more switches in a pinball machine than keys on a keyboard, MPF lets you add modified keys to your keyboard: map. This means that MPF will see Z, SHIFT+Z, CRTL+Z, SHIFT+CTRL+Z, etc. all as different switches.
  • Remember that the media controller’s pop-up window has to be in focus. Make sure it’s the active window on your desktop and try hitting your keys again.
  • Remember that your physical flippers will not flip if you hit the keyboard keys for your flipper buttons.

Check out the complete config.yaml file so far

If you want to see a complete config.yaml file up to this point, it’s in the mpf-examples/tutorial folder with the name step6.yaml.

You can run this file directly by switching to that folder and then running the following command:

C:\mpf-examples\tutorial>mpf both -c step6