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Snux System 11 Driver Board

This board is most likely not available

This section about the "Snux" System 11 driverboard probably no longer applies, as that board was only released as a hobby kit in the early 2010s and does not appear to be available anymore. (Or is it? Update this page if you know more.)

Other solutions for controlling System 11 machines exist though.

Related Config File Sections:

MPF can be used with Williams System 11 machines. (Also since Data East's system was a clone of Williams System 11, everything here also applies to those machines.) This How To guide walks you through the process of buying the hardware you need and configuring MPF to work with it.

(A) Understand the challenges of System 11 hardware

The original System 11 Williams/Bally hardware (and the Data East clone) was created in a time when computing resources were scarce and hardware was expensive. It's sort of a "crossover" between the early solid state machines of the '80s and the more modern WPC machines. Because of this, there are a lot of, umm... "quirks" to the design which were necessary at the time but which may seem a bit strange in today's world. Even though we tend to lump all "System 11" machines into a single category, there were actually four different generations of System 11 machines, called System 11, System 11A, System 11B, and System 11C. (And just to make things even more fun, some changes were made part way through System 11B.) So technically-speaking there are actually five different types of System 11 machines out there!


On modern WPC pinball machines, flipper buttons are just regular switches that send their inputs to the CPU, and flipper coils are just regular coils that are controlled by the CPU. Typical flippers in MPF are configured via the flippers: section of the config file, and when flippers are enabled, hardware rules are written to the pinball controller to allow them to be fired "instantly" when the flipper buttons are hit. Back in the days of System 11, the CPUs in those machines didn't have enough horsepower to constantly poll the status of the flipper buttons and to drive the flippers in software while also doing everything else the CPU needed to do to run the game. So instant, System 11 machines had the flipper buttons directly connected to the flipper coils, meaning that hitting the flipper button would activate the flipper coil directly without any intervention of the CPU. Of course the machine still needed a way to enable or disable the flippers, since the flippers needed to be disabled when a game was not going on and when the player tilted. To do this, System 11 machines used a "flipper enable" relay. This was a mechanical relay connected to a driver output on the driver board. When that driver was enabled, the relay was energized and the flippers worked. When that relay was disabled, the relay de-energized, the electrical connection to the flipper buttons was broken, and the flippers stopped working. While this meant that the CPU didn't have to directly control the flippers, it also meant that many modern conveniences are not available on that hardware. For example, on modern machines you can control the strength of the flipper by adjusting the pulse times of the flipper coils with millisecond-level accuracy. But these older machines gave full power to the flipper until the flipper bat hit the end-of-stroke (EOS) switch, and that switch mechanically cut off power to the high-power winding (while keeping power enabled on the low-power hold winding). So in those days, changing the strength of a flipper was done by physically swapping out the flipper coil with a stronger or weaker one.

"Special" Solenoids

Flippers are not the only types of devices that require instant response in pinball machines. They also need instant response action for slingshots, pop bumpers, and (sometimes) diverters. In many System 11 machines, these types of devices were also controlled by the flipper enable relay. So when that relay was enabled, it enabled not just the flippers but also the pop bumpers and slingshots. Of course pop bumpers and slingshots are a bit different than flippers:

  • The CPU needs to know when pop bumpers and slingshots are hit so it can assign points, flash lights, play sounds, etc.
  • The CPU needs to be able to manually fire pop bumpers and slingshots for things like ball search and the coil test options in the operators menu.

In other words, it seems that pop bumpers and slingshots really need to be controlled the "new" way since the CPU needs to know when they're hit and the CPU needs to be able to manually fire them. But of course firing a pop bumper or slingshot when their switch is hit needs to happen instantly, and as we just discussed, that was not possible in the System 11 days. So how did they get around it? System 11 machines call these types of solenoids special solenoids (that is literally what they're called in the manual) because they're actually controllable via two different ways:

  • When the flipper enable relay is enabled, a hit to these devices' switches creates a direct electrical connection to their coils which fires them.
  • These devices' coils also have a second (additional) control input which lets the CPU fire them from the service test menu or for ball search.

Furthermore you'll also notice that there are switches in the switch matrix for many of these devices which are used to let the CPU know that these devices have been hit to assign points and to do effects. At this point you might think, "Great! So these devices have CPU-controlled coils, and they have switches in the switch matrix, so I can just set them up like regular devices since I'm using modern hardware!" Not so fast. In many System 11 machines, the switches in the switch matrix which tell the CPU that a pop bumper or slingshot has been hit are not the same switches that fire the coil! For example, the switch attached to the skirt of the pop bumper that the ball hits is a high-voltage switch that is physically connected to the pop bumper's coil. The CPU does not see that switch at all. When that switch is hit (if the flipper enable relay is active), then it grounds the connection to the coil and the coil fires. When the coil fires, its shaft hits a second switch underneath, and that's the switch that is connected to the switch matrix and the CPU. (And actually there's a third switch under there too which is the EOS switch which cuts power to the coil after it's been fired.) So in reality, yeah, you may see a switch in the switch matrix for a pop bumper, but that switch is not, "Hey the pop bumper skirt switch was hit, so fire the pop bumper now," rather, that switch is, "Hey the pop bumper just fired. Just FYI." The exact details of how these special solenoids work depends on the specific machine and which version of System 11 it is. For example, some devices (like pop bumpers and slingshots) should always be on whenever the flippers are enabled, so the flipper enable relay enables them too. Other devices (like diverters) should only be active sometimes, so they have their own enable driver (which is like the flipper enable relay, but separate from it) so they can be controlled individually.

The A/C Relay & Switched Solenoids

But wait! There's more! System 11 machines also have this concept of the A/C relay. This is not A/C in the terms of alternating current. It has nothing to do with that. It's actually used to control things called A-side and C-side devices. The basic concept is that since the driver circuitry was expensive, Williams decided they could get double their "bang for their buck" by connecting two devices so a single output. So you might see on a schematic that a single driver output is connected to both a ball kickout coil and a flasher. Then there was a relay (called the A/C relay, or sometimes the C-select relay) connected in there too. If the A/C relay was in the A position, then firing that driver would fire the coil connected to the A side of that output, and if the A/C relay was in the C position, then firing that driver would fire the device connected to the C side of that output. This worked because they had a single A/C relay that was connected to an entire bank of 8 drivers. So they could actually control 16 different devices (8 drivers with two devices each) from just 9 driver outputs (8 drivers plus 1 for the A/C relay). They were also smart about what types of devices they connected to each side of the relay. System 11 machines put the "important" devices on the A side (things that interact with the ball on the playfield, like diverters, kickout holes, motors, etc.), and they put the "less important" things on the C side (flashers and the knocker coil). So this means they will constantly enable and disable the A/C relay to do different effects, but if two things need to happen at exactly the same time, they can service the A-side first (since those are the important ones) and then flip the relay to the C-side and pick those up after a few hundred milliseconds of delay.

Controlled Solenoids

In addition to switched, controlled, and flipper solenoids, System 11 machines also included what they called "controlled" solenoids which was their name for normal, modern-style solenoids. So in addition to all the craziness of the other control schemes, some solenoids were regular. No special switches. No special handling. Just regular solenoids.

GI (General Illumination)

In WPC machines, GI strings are controlled via separate GI drivers (which are alternating current and which may or may not be dimmable). In System 11, GI strings were regular driver outputs, just like any solenoid. The catch is that most (maybe all?) GI strings on System 11 machines are "backwards" in the sense that the GI is on when the driver is disabled, and you enable the driver to turn off the GI. This was done because the GI is almost always on all the time, though there are periods when you might want to turn it off for special effects. So to save on wear of the relays and make things simpler, in System 11 machines, the GI is just always on until the CPU turns it off.

Putting it all together

If you look at the solenoid table in the operators manual of a System 11 machine, you'll see that all the drivers fall into these categories. Some are are switched, some are controlled, some are flippers, and some are special. Check out the solenoid table from PinBot. Note that the first 16 solenoids are the A/C switched solenoids, and there are two coils for each number 1-8 with an "A" and "C" suffix denoting which side they're on. Then the next 8 (numbers 9-16) are controlled solenoids. These are the regular modern-style drivers which also include the GI (remember they're active off) and important flashers they don't want to share with A/C switched drivers. Then you have the next batch 17-22 which are the special solenoids that are enabled when the flipper enable relay is enabled, but they can also be manually controlled for ball search and testing. And finally you have the left and right flipper solenoids which don't have numbers because they're not connected to the driver board. Also notice solenoid 14 is the "Solenoid Select Relay." That's the A/C select which when inactive means that drivers 1-8 are connected to the A-side devices, and when active means drivers 1-8 are connected to the C-side devices.

(B) The Snux board

Okay, so now that you're caught up with the intricacies of System 11 hardware, how do you actually control this via MPF? The usual way you control an existing machine is to remove the original CPU board and to replace it with either a P-ROC controller. The new pinball controller plugs into the backbox and uses the existing driver board. The problem with System 11 is that unlike more modern machines, the System 11 CPU board and driver board were actually combined into one single huge board. So when you take out the CPU board, you also lose the driver board. This means if you put a P-ROC controller into a System 11 machine, you don't have a driver board. :( This is where the Snux board comes in. The Snux board (which is our name for it) is a System 11 driver board created by Mark Sunnucks. (His online handle is Snux which is why we call it the Snux board.) Mark developed this board a few years ago because he wanted to control an F-14 machine with a P-ROC. The Snux board can be thought of kind of like the WPC power driver board except that it's made to work with System 11 machines instead of WPC machines. Since the original System 11 combo CPU board / driver board was so huge, when you remove it from your System 11 machine there's plenty of room to put the Snux board and a P-ROC controller in it's place. The Snux board connects to the P-ROC controller via the standard 34-pin ribbon cable, and then it has all the connectors (in their proper locations) to connect the existing wiring connectors from the System 11 machine to it. So in order to control a System 11 machine with MPF, you need to get a Snux board. Mark has a day job and built this board as a hobby, but he sells them to other folks who are interested in modernizing System 11 machines. Mark lives in the UK, so the exact price you pay depends on the exchange rate, shipping to your country but it's around \$180 US (Then you also have to buy a P-ROC to drive it.) You can contact Mark via PM (on Pinside as Snux). In addition to the board there are 3 or 4 cables you'll need, Mark can advise.


All System 11 machines used various combinations of segment displays and these cannot be directly controlled via the P-ROC. If you do want to use the original segment displays, Jim at sells an adaptor board that will connect between the P-ROC and the displays. Otherwise you can use the various other display options that MPF provides.

(C) Understand how MPF works with the Snux board

Once you have your P-ROC controller and the Snux board installed in your System 11 machine, you need to build your machine-wide configuration file for your machine. MPF has a Snux interface which is actually implemented as a platform overlay. A platform overlay, in MPF, is like a second layer that sits on top of the regular platform interface and modifies the way it works. So since the Snux board works with the P-ROC controller, the main platform interface MPF uses is the P-ROC platform. Then the Snux platform overlay layers on top of it to handle the special cases that arise when using the P-ROC with a Snux board. (For example, automatically controlling the A/C relay to make sure it's in the right position when an A-side or C-side driver is activated, and preventing the activation of C-side drivers when the A/C relay is in the A position and vice-versa.) The Snux driver overlay completely hides the nuances of the System 11 hardware from you. You can freely enable, disable, or pulse any A-side or C-side driver you want, and MPF will automatically control the A/C relay and make sure it's in the proper position. Since A-side drivers are more important in the machine, MPF will always give them priority. If simultaneous requests for an A-side and C-side driver come in at the same time, MPF will service the A-side driver and add the C-side driver to a queue, and then when the A-side driver is done, MPF will flip the relay to the C-side and then service the C-side driver. Similarly if drivers on the C-side are active and an A-side request comes in, MPF will deactivate the C-side drivers, flip the relay, and then service the A-side drivers. The takeaways from this are (1) A-side drivers always have priority, and (2) the handling of the A/C relay is automatic.

(D) System 11-specific MPF configuration

Once you have your hardware setup, there are a few things you need to do in your config file.

1. Configure your hardware interface

The first thing to do is to configure your hardware options in the hardware section of your machine-wide config. You configure the main platform as p_roc, but then for driverboards you configure it as snux, like this:

  platform: virtual
  driverboards: wpc
  coils: snux
  switches: snux

2. Configure snux options

The MPF machine-wide config file contains a few options for the Snux driverboard. These options are set in the default mpfconfig.yaml file which means you don't have to add them to your own config file, but we're including them here just for completeness:

    number: c24
    default_hold_power: 1.0

  diag_led_driver: c_diag_led_driver

The Snux board maps driver c_diag_led_driver which is driver 24 to the "diag" LED on the board. When you power on your machine, the diag LED is off. Then when MPF connects to the board, this LED turns on solid. Finally when MPF is done loading and it starts the main machine loop, this LED flashes twice per second. If this LED stops flashing, that means MPF crashed. :)

3. Configure system11 options

Next you need to add a system11: section to your machine-wide config and specific some System 11 options. At this point you might be wondering, "Why aren't these options in the snux section?" The reason is that the settings in the snux section apply to the Snux board itself, whereas the settings in this system11 section apply to any System 11 machine that MPF might control. Of course at this point, that's only possible via the Snux board, but they're technically separate settings since the architecture allows for future System 11 boards that may exist at some point. Here's the system11 configuration section from Pin*Bot:

  ac_relay_delay_ms: 75
  ac_relay_driver_number: c14

The ac_relay_delay_ms is the number of milliseconds MPF waits before and after flipping the A/C select relay to allow for it to fully switch positions. For example, if you have a C-side driver active and you need to activate an A-side driver, MPF cannot simply deactivate the A/C relay and the C-side device and activate the A-side device all at the same time. If it does then power will "leak" from one side to the other as the relay is transitioning. So what actually happens in this scenario is that MPF will deactivate the C-side devices, then wait 75ms for them to really be "off", then deactivate the A/C relay, then wait another 75ms for the relay to flip, then activate the A-side device. We did some experimentation with different delay times. On Pin*Bot, 50ms was definitely too short as we'd see some weak flashes from C-side flashers connected to A-side devices we were activating on the transition. 75ms seems fine, though really this is all faster than humans can perceive (and C-side devices aren't as time sensitive), so even setting this to 100ms is probably fine. 75ms is the default if you don't add this section to your config. The ac_relay_driver_number is the driver (with a "C" added to it) from the manual for the A/C select relay. Be sure you check the A/C relay driver number from your manual. It's different in the two System 11 machines we tested. (C14 in PinBot* and C12 in Jokerz!) Also it's labeled differently in different manuals. In the Jokerz! manual it's called the "A/C Select Relay," and in the PinBot* manual it's called the "Solenoid Select Relay."

4. Enable flippers

The Snux board uses driver 23 to enable the flippers:

    number: c23
    type: driver
    enable_events: ball_started
    disable_events: ball_will_end

You can change the events when the flipper should enable and disable. By default we will enable the flippers on ball start and disable them on ball end.

5. Configuring driver numbers


Please ensure that you have established common ground between logic and coil power before turning on high voltage on your coils (especially on homebrew machines). Ignoring this might lock on your coils, overheat them, burn down your house or kill you. We are serious, floating grounds are dangerous. If you are not an electrical engineer read the guide about voltages and power.

In a nutshell: You need to connect your logic ground (5V/12V) and your high voltage ground (48V or 80V). A power entry or power filter board is a convenient solution to solve this (and more) issues.

Always turn all PSUs off when connecting power or you might fry all boards at once. This is generally a good idea but even more important when connecting more than one power supply to a board.


When you configure coils, flashers, and gis in your MPF hardware config, you can enter the numbers straight out of the operators manual. The only thing to note here is that you must add a "C" to the beginning of the driver number (even for flashers and GI), since that's what triggers MPF to do a WPC-style lookup to convert the driver number to the internal hardware number the platform uses. (It's an WPC-style lookup since the Snux driver board emulates a WPC driver board.) Also for switched solenoids which use the A/C relay, you also need to add an "A" or a "C" to the end of the driver number. Here's a snippet (incomplete) from the PinBot* machine-wide config file:

    number: c01a
    number: c01c
    number: c02a
    number: c13
    allow_enable: true
    number: c02c
    number: c03c
    number: c04c
    number: c05c
    number: c06c
    number: c07c
    number: c08c
    number: c09
    number: c15
    number: c16

Again, don't forgot the "a" or the "c" at the end of the switched solenoids, since that's how MPF knows it needs to use the A/C relay logic for those devices!

6. Configure lamps

Configuring the numbers for matrix lamps is pretty straightforward and something you can also use the manual for. The format for lamp number is the letter "L" followed by the column, then the row. In other words, light number L25 is the light in column 2, row 5. This is a bit confusing because these are not the numbers that the lamps use in the manual! The lights in the lamp matrix table are simply numbered from 1 to 64. So you need to use the chart in the manual to get the column and row positions, not to get the actual light numbers! (When Williams switched to WPC, they switched to lamp numbers based on the column and row. So in WPC machines, the lamps in column 1 are numbers 11-18, the lamps in column 2 are 21-28, etc. System 11 numbers would be 1-8 for column 1, 9-16 for column 2, etc. Basically since System 11 machines have an 8x8 lamp matrix, there should be no numbers 9 or 0 anywhere in your lamp numbers. Here's a snippet of the configuration from Pin*Bot:

    number: L11
    number: L12
    number: L13
    number: L14
    number: L15
    number: L16
    number: L17
    number: L18
    number: L21
    number: L22

Again, don't forget that they should all start with "L", and they're based on the positions in the matrix, not on the numbers from the manual.

7. Configure switches

Switch numbering in System 11 machines is the same as lamp numbering, except the numbers start with "S". Again the numeric portion of the number is based on the column/row, not the switch number in the manual. So even though the manual says that the switch in column 5, row 6 is number 38, you actually enter "L56". Here's another snippet from PinBot*:

    number: S24
    label: Left Outlane
    tags: playfield_active
    number: S25
    label: Left Inlane
    tags: playfield_active
    number: S26
    label: Right Inlane
    tags: playfield_active
    number: S27
    label: Right Outlane
    tags: playfield_active

You might have to do some detective work to figure out where the switches are and how they work. For example, remember that switches from slingshots or pop bumpers are most likely activated by the physical action of the device's coil, not by the switch above the playfield. So on Pin*Bot hitting the pop bumper skirt does not activate the pop bumper switch, but manually pushing the pop bumper ring down with your fingers will activate that switch. Also you might see switches with names along the lines of "Right Lane Change." If the lane change in that machine is activated by a slingshot, then most likely the Right Lane Change switch is under the playfield and activated by the physical slingshot arm hitting it. Same for flipper-controlled lane changes. You'll have to hunt to see whether there's a second switch in the flipper EOS stack under the playfield or perhaps a second switch in the stack behind the flipper button.

8. Create your System 11-style trough

Troughs in System 11 machines are not like troughs in modern machines. Rather than a single ball device which acts as the drain as well as the feeder to the plunger lane, System 11 machines have two separate devices with two solenoids. One device is typically called the "outhole" (or "drain") which receives the ball from the playfield, and it kicks the ball over to the trough where the ball is stored. Then the trough has a second coil which kicks the ball into the plunger lane when it needs it. We have a separate How To guide which details how to setup a System 11 1980s-style trough, link below (since many games do this, even ones that aren't System 11), so you can read that for more details. The result though will look something like this:

#! switches:
#!   outhole:
#!     number: 1
#!   trough1:
#!     number: 2
#!   trough2:
#!     number: 3
#!   plunger_lane:
#!     number: 4
#! coils:
#!   outhole:
#!     number: 1
#!   trough:
#!     number: 2
    ball_switches: outhole
    eject_coil: outhole
    confirm_eject_type: target
    eject_targets: trough
    tags: drain
    ball_switches: trough1, trough2
    eject_coil: trough
    eject_targets: plunger_lane
    tags: home, trough
    ball_switches: plunger_lane
    mechanical_eject: true
    eject_timeouts: 3s

The key is that you're setting up a "chain" of devices (from outhole to trough to plunger lane), and you're breaking up the special tags so that each device is tagged with it's exact role. (And hey! Now you know why these are all separate tags in MPF instead of a single tag called "trough".)

See Setting up a System 11 Style Trough for details.

(E) Final Steps and additional information

MPF's System 11 interface is new, and we haven't yet built a complete game using it. There are most likely things that we haven't thought of yet, so if you're using MPF with a System 11 machine, please post to the forum if you find anything that's weird or that doesn't work as expected.

Snux on Pinside.

This is an example code block with the main Sys11 elements in.

  platform: virtual
  driverboards: wpc
  coils: snux
  switches: snux

  ac_relay_delay_ms: 75
  ac_relay_driver: c_ac_relay

  diag_led_driver: c_diag_led_driver

    number: c23
    type: driver
    enable_events: ball_started
    disable_events: ball_will_end

    number: c24
    default_hold_power: 1.0
    number: c25
    default_hold_power: 1.0
    number: c11a
    number: c12a
    default_hold_power: 0.5
    number: c11c
    number: c12c
    default_hold_power: 0.5

What if it did not work?

Have a look at our hardware troubleshooting guide.

Something missing or wrong? You can fix it!

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