An I/O controller for virtual pinball machines: accelerometer nudge sensing, analog plunger input, button input encoding, LedWiz compatible output controls, and more.

Dependencies:   mbed FastIO FastPWM USBDevice

Fork of Pinscape_Controller by Mike R


This is Version 2 of the Pinscape Controller, an I/O controller for virtual pinball machines. (You can find the old version 1 software here.) Pinscape is software for the KL25Z that turns the board into a full-featured I/O controller for virtual pinball, with support for accelerometer-based nudging, a real plunger, button inputs, and feedback device control.

In case you haven't heard of the concept before, a "virtual pinball machine" is basically a video pinball simulator that's built into a real pinball machine body. A TV monitor goes in place of the pinball playfield, and a second TV goes in the backbox to serve as the "backglass" display. A third smaller monitor can serve as the "DMD" (the Dot Matrix Display used for scoring on newer machines), or you can even install a real pinball plasma DMD. A computer is hidden inside the cabinet, running pinball emulation software that displays a life-sized playfield on the main TV. The cabinet has all of the usual buttons, too, so it not only looks like the real thing, but plays like it too. That's a picture of my own machine to the right. On the outside, it's built exactly like a real arcade pinball machine, with the same overall dimensions and all of the standard pinball cabinet hardware.

A few small companies build and sell complete, finished virtual pinball machines, but I think it's more fun as a DIY project. If you have some basic wood-working skills and know your way around PCs, you can build one from scratch. The computer part is just an ordinary Windows PC, and all of the pinball emulation can be built out of free, open-source software. In that spirit, the Pinscape Controller is an open-source software/hardware project that offers a no-compromises, all-in-one control center for all of the unique input/output needs of a virtual pinball cabinet. If you've been thinking about building one of these, but you're not sure how to connect a plunger, flipper buttons, lights, nudge sensor, and whatever else you can think of, this project might be just what you're looking for.

You can find much more information about DIY Pin Cab building in general in the Virtual Cabinet Forum on Also visit my Pinscape Resources page for more about this project and other virtual pinball projects I'm working on.


  • Pinscape Release Builds: This page has download links for all of the Pinscape software. To get started, install and run the Pinscape Config Tool on your Windows computer. It will lead you through the steps for installing the Pinscape firmware on the KL25Z.
  • Config Tool Source Code. The complete C# source code for the config tool. You don't need this to run the tool, but it's available if you want to customize anything or see how it works inside.


The new Version 2 Build Guide is now complete! This new version aims to be a complete guide to building a virtual pinball machine, including not only the Pinscape elements but all of the basics, from sourcing parts to building all of the hardware.

You can also refer to the original Hardware Build Guide (PDF), but that's out of date now, since it refers to the old version 1 software, which was rather different (especially when it comes to configuration).

System Requirements

The new config tool requires a fairly up-to-date Microsoft .NET installation. If you use Windows Update to keep your system current, you should be fine. A modern version of Internet Explorer (IE) is required, even if you don't use it as your main browser, because the config tool uses some system components that Microsoft packages into the IE install set. I test with IE11, so that's known to work. IE8 doesn't work. IE9 and 10 are unknown at this point.

The Windows requirements are only for the config tool. The firmware doesn't care about anything on the Windows side, so if you can make do without the config tool, you can use almost any Windows setup.

Main Features

Plunger: The Pinscape Controller started out as a "mechanical plunger" controller: a device for attaching a real pinball plunger to the video game software so that you could launch the ball the natural way. This is still, of course, a central feature of the project. The software supports several types of sensors: a high-resolution optical sensor (which works by essentially taking pictures of the plunger as it moves); a slide potentionmeter (which determines the position via the changing electrical resistance in the pot); a quadrature sensor (which counts bars printed on a special guide rail that it moves along); and an IR distance sensor (which determines the position by sending pulses of light at the plunger and measuring the round-trip travel time). The Build Guide explains how to set up each type of sensor.

Nudging: The KL25Z (the little microcontroller that the software runs on) has a built-in accelerometer. The Pinscape software uses it to sense when you nudge the cabinet, and feeds the acceleration data to the pinball software on the PC. This turns physical nudges into virtual English on the ball. The accelerometer is quite sensitive and accurate, so we can measure the difference between little bumps and hard shoves, and everything in between. The result is natural and immersive.

Buttons: You can wire real pinball buttons to the KL25Z, and the software will translate the buttons into PC input. You have the option to map each button to a keyboard key or joystick button. You can wire up your flipper buttons, Magna Save buttons, Start button, coin slots, operator buttons, and whatever else you need.

Feedback devices: You can also attach "feedback devices" to the KL25Z. Feedback devices are things that create tactile, sound, and lighting effects in sync with the game action. The most popular PC pinball emulators know how to address a wide variety of these devices, and know how to match them to on-screen action in each virtual table. You just need an I/O controller that translates commands from the PC into electrical signals that turn the devices on and off. The Pinscape Controller can do that for you.

Expansion Boards

There are two main ways to run the Pinscape Controller: standalone, or using the "expansion boards".

In the basic standalone setup, you just need the KL25Z, plus whatever buttons, sensors, and feedback devices you want to attach to it. This mode lets you take advantage of everything the software can do, but for some features, you'll have to build some ad hoc external circuitry to interface external devices with the KL25Z. The Build Guide has detailed plans for exactly what you need to build.

The other option is the Pinscape Expansion Boards. The expansion boards are a companion project, which is also totally free and open-source, that provides Printed Circuit Board (PCB) layouts that are designed specifically to work with the Pinscape software. The PCB designs are in the widely used EAGLE format, which many PCB manufacturers can turn directly into physical boards for you. The expansion boards organize all of the external connections more neatly than on the standalone KL25Z, and they add all of the interface circuitry needed for all of the advanced software functions. The big thing they bring to the table is lots of high-power outputs. The boards provide a modular system that lets you add boards to add more outputs. If you opt for the basic core setup, you'll have enough outputs for all of the toys in a really well-equipped cabinet. If your ambitions go beyond merely well-equipped and run to the ridiculously extravagant, just add an extra board or two. The modular design also means that you can add to the system over time.

Expansion Board project page

Update notes

If you have a Pinscape V1 setup already installed, you should be able to switch to the new version pretty seamlessly. There are just a couple of things to be aware of.

First, the "configuration" procedure is completely different in the new version. Way better and way easier, but it's not what you're used to from V1. In V1, you had to edit the project source code and compile your own custom version of the program. No more! With V2, you simply install the standard, pre-compiled .bin file, and select options using the Pinscape Config Tool on Windows.

Second, if you're using the TSL1410R optical sensor for your plunger, there's a chance you'll need to boost your light source's brightness a little bit. The "shutter speed" is faster in this version, which means that it doesn't spend as much time collecting light per frame as before. The software actually does "auto exposure" adaptation on every frame, so the increased shutter speed really shouldn't bother it, but it does require a certain minimum level of contrast, which requires a certain minimal level of lighting. Check the plunger viewer in the setup tool if you have any problems; if the image looks totally dark, try increasing the light level to see if that helps.

New Features

V2 has numerous new features. Here are some of the highlights...

Dynamic configuration: as explained above, configuration is now handled through the Config Tool on Windows. It's no longer necessary to edit the source code or compile your own modified binary.

Improved plunger sensing: the software now reads the TSL1410R optical sensor about 15x faster than it did before. This allows reading the sensor at full resolution (400dpi), about 400 times per second. The faster frame rate makes a big difference in how accurately we can read the plunger position during the fast motion of a release, which allows for more precise position sensing and faster response. The differences aren't dramatic, since the sensing was already pretty good even with the slower V1 scan rate, but you might notice a little better precision in tricky skill shots.

Keyboard keys: button inputs can now be mapped to keyboard keys. The joystick button option is still available as well, of course. Keyboard keys have the advantage of being closer to universal for PC pinball software: some pinball software can be set up to take joystick input, but nearly all PC pinball emulators can take keyboard input, and nearly all of them use the same key mappings.

Local shift button: one physical button can be designed as the local shift button. This works like a Shift button on a keyboard, but with cabinet buttons. It allows each physical button on the cabinet to have two PC keys assigned, one normal and one shifted. Hold down the local shift button, then press another key, and the other key's shifted key mapping is sent to the PC. The shift button can have a regular key mapping of its own as well, so it can do double duty. The shift feature lets you access more functions without cluttering your cabinet with extra buttons. It's especially nice for less frequently used functions like adjusting the volume or activating night mode.

Night mode: the output controller has a new "night mode" option, which lets you turn off all of your noisy devices with a single button, switch, or PC command. You can designate individual ports as noisy or not. Night mode only disables the noisemakers, so you still get the benefit of your flashers, button lights, and other quiet devices. This lets you play late into the night without disturbing your housemates or neighbors.

Gamma correction: you can designate individual output ports for gamma correction. This adjusts the intensity level of an output to make it match the way the human eye perceives brightness, so that fades and color mixes look more natural in lighting devices. You can apply this to individual ports, so that it only affects ports that actually have lights of some kind attached.

IR Remote Control: the controller software can transmit and/or receive IR remote control commands if you attach appropriate parts (an IR LED to send, an IR sensor chip to receive). This can be used to turn on your TV(s) when the system powers on, if they don't turn on automatically, and for any other functions you can think of requiring IR send/receive capabilities. You can assign IR commands to cabinet buttons, so that pressing a button on your cabinet sends a remote control command from the attached IR LED, and you can have the controller generate virtual key presses on your PC in response to received IR commands. If you have the IR sensor attached, the system can use it to learn commands from your existing remotes.

Yet more USB fixes: I've been gradually finding and fixing USB bugs in the mbed library for months now. This version has all of the fixes of the last couple of releases, of course, plus some new ones. It also has a new "last resort" feature, since there always seems to be "just one more" USB bug. The last resort is that you can tell the device to automatically reboot itself if it loses the USB connection and can't restore it within a given time limit.

More Downloads

  • Custom VP builds: I created modified versions of Visual Pinball 9.9 and Physmod5 that you might want to use in combination with this controller. The modified versions have special handling for plunger calibration specific to the Pinscape Controller, as well as some enhancements to the nudge physics. If you're not using the plunger, you might still want it for the nudge improvements. The modified version also works with any other input controller, so you can get the enhanced nudging effects even if you're using a different plunger/nudge kit. The big change in the modified versions is a "filter" for accelerometer input that's designed to make the response to cabinet nudges more realistic. It also makes the response more subdued than in the standard VP, so it's not to everyone's taste. The downloads include both the updated executables and the source code changes, in case you want to merge the changes into your own custom version(s).

    Note! These features are now standard in the official VP releases, so you don't need my custom builds if you're using 9.9.1 or later and/or VP 10. I don't think there's any reason to use my versions instead of the latest official ones, and in fact I'd encourage you to use the official releases since they're more up to date, but I'm leaving my builds available just in case. In the official versions, look for the checkbox "Enable Nudge Filter" in the Keys preferences dialog. My custom versions don't include that checkbox; they just enable the filter unconditionally.
  • Output circuit shopping list: This is a saved shopping cart at with the parts needed to build one copy of the high-power output circuit for the LedWiz emulator feature, for use with the standalone KL25Z (that is, without the expansion boards). The quantities in the cart are for one output channel, so if you want N outputs, simply multiply the quantities by the N, with one exception: you only need one ULN2803 transistor array chip for each eight output circuits. If you're using the expansion boards, you won't need any of this, since the boards provide their own high-power outputs.
  • Cary Owens' optical sensor housing: A 3D-printable design for a housing/mounting bracket for the optical plunger sensor, designed by Cary Owens. This makes it easy to mount the sensor.
  • Lemming77's potentiometer mounting bracket and shooter rod connecter: Sketchup designs for 3D-printable parts for mounting a slide potentiometer as the plunger sensor. These were designed for a particular slide potentiometer that used to be available from an seller but is no longer listed. You can probably use this design as a starting point for other similar devices; just check the dimensions before committing the design to plastic.

Copyright and License

The Pinscape firmware is copyright 2014, 2021 by Michael J Roberts. It's released under an MIT open-source license. See License.

Warning to VirtuaPin Kit Owners

This software isn't designed as a replacement for the VirtuaPin plunger kit's firmware. If you bought the VirtuaPin kit, I recommend that you don't install this software. The VirtuaPin kit uses the same KL25Z microcontroller that Pinscape uses, but the rest of its hardware is different and incompatible. In particular, the Pinscape firmware doesn't include support for the IR proximity sensor used in the VirtuaPin plunger kit, so you won't be able to use your plunger device with the Pinscape firmware. In addition, the VirtuaPin setup uses a different set of GPIO pins for the button inputs from the Pinscape defaults, so if you do install the Pinscape firmware, you'll have to go into the Config Tool and reassign all of the buttons to match the VirtuaPin wiring.

--- a/main.cpp	Fri Aug 08 20:59:39 2014 +0000
+++ b/main.cpp	Mon Aug 18 21:46:10 2014 +0000
@@ -171,7 +171,16 @@
 //    byte 2 = new LedWiz unit number, 0x01 to 0x0f
 //    byte 3 = feature enable bit mask:
 //             0x01 = enable CCD (default = on)
+// Plunger calibration mode: the host can activate plunger calibration mode
+// by sending this packet.  This has the same effect as pressing and holding
+// the plunger calibration button for two seconds, to allow activating this
+// mode without attaching a physical button.
+//    length = 8 bytes
+//    byte 0 = 65 (0x41)
+//    byte 1 = 2 (0x02)
 #include "mbed.h"
 #include "math.h"
@@ -220,6 +229,22 @@
 const uint16_t USB_VERSION_NO = 0x0006;
 const uint8_t DEFAULT_LEDWIZ_UNIT_NUMBER = 0x07;
+// Number of pixels we read from the sensor on each frame.  This can be
+// less than the physical pixel count if desired; we'll read every nth
+// piexl if so.  E.g., with a 1280-pixel physical sensor, if npix is 320,
+// we'll read every 4th pixel.  It takes time to read each pixel, so the
+// fewer pixels we read, the higher the refresh rate we can achieve.
+// It's therefore better not to read more pixels than we have to.
+// VP seems to have an internal resolution in the 8-bit range, so there's
+// no apparent benefit to reading more than 128-256 pixels when using VP.
+// Empirically, 160 pixels seems about right.  The overall travel of a
+// standard pinball plunger is about 3", so 160 pixels gives us resolution
+// of about 1/50".  This seems to take full advantage of VP's modeling
+// ability, and is probably also more precise than a human player's
+// perception of the plunger position.
+const int npix = 160;
 // On-board RGB LED elements - we use these for diagnostic displays.
 DigitalOut ledR(LED1), ledG(LED2), ledB(LED3);
@@ -302,23 +327,24 @@
     { PTD5, true },      // pin J2-4,  LW port 8  (PWM capable - TPM 0.5 = channel 6)
     { PTD0, true },      // pin J2-6,  LW port 9  (PWM capable - TPM 0.0 = channel 1)
     { PTD3, true },      // pin J2-10, LW port 10 (PWM capable - TPM 0.3 = channel 4)
-    { PTC8, false },     // pin J1-14, LW port 11
-    { PTC9, false },     // pin J1-16, LW port 12
-    { PTC7, false },     // pin J1-1,  LW port 13
-    { PTC0, false },     // pin J1-3,  LW port 14
-    { PTC3, false },     // pin J1-5,  LW port 15
-    { PTC4, false },     // pin J1-7,  LW port 16
-    { PTC5, false },     // pin J1-9,  LW port 17
-    { PTC6, false },     // pin J1-11, LW port 18
-    { PTC10, false },    // pin J1-13, LW port 19
-    { PTC11, false },    // pin J1-15, LW port 20
-    { PTC12, false },    // pin J2-1,  LW port 21
-    { PTC13, false },    // pin J2-3,  LW port 22
-    { PTC16, false },    // pin J2-5,  LW port 23
-    { PTC17, false },    // pin J2-7,  LW port 24
-    { PTA16, false },    // pin J2-9,  LW port 25
-    { PTA17, false },    // pin J2-11, LW port 26
-    { PTE31, false },    // pin J2-13, LW port 27
+    { PTD2, false },     // pin J2-8,  LW port 11
+    { PTC8, false },     // pin J1-14, LW port 12
+    { PTC9, false },     // pin J1-16, LW port 13
+    { PTC7, false },     // pin J1-1,  LW port 14
+    { PTC0, false },     // pin J1-3,  LW port 15
+    { PTC3, false },     // pin J1-5,  LW port 16
+    { PTC4, false },     // pin J1-7,  LW port 17
+    { PTC5, false },     // pin J1-9,  LW port 18
+    { PTC6, false },     // pin J1-11, LW port 19
+    { PTC10, false },    // pin J1-13, LW port 20
+    { PTC11, false },    // pin J1-15, LW port 21
+    { PTC12, false },    // pin J2-1,  LW port 22
+    { PTC13, false },    // pin J2-3,  LW port 23
+    { PTC16, false },    // pin J2-5,  LW port 24
+    { PTC17, false },    // pin J2-7,  LW port 25
+    { PTA16, false },    // pin J2-9,  LW port 26
+    { PTA17, false },    // pin J2-11, LW port 27
+    { PTE31, false },    // pin J2-13, LW port 28
     { PTD6, false },     // pin J2-17, LW port 29
     { PTD7, false },     // pin J2-19, LW port 30
     { PTE0, false },     // pin J2-18, LW port 31
@@ -343,6 +369,12 @@
 // ---------------------------------------------------------------------------
+// utilities
+// number of elements in an array
+#define countof(x) (sizeof(x)/sizeof((x)[0]))
+// ---------------------------------------------------------------------------
 // LedWiz emulation
@@ -381,7 +413,7 @@
 // initialize the output pin array
 void initLwOut()
-    for (int i = 0 ; i < sizeof(lwPin) / sizeof(lwPin[0]) ; ++i)
+    for (int i = 0 ; i < countof(lwPin) ; ++i)
         PinName p = ledWizPortMap[i].pin;
         lwPin[i] = (ledWizPortMap[i].isPWM
@@ -467,6 +499,15 @@
         iap.program_flash(addr, this, sizeof(*this));
+    // reset calibration data for calibration mode
+    void resetPlunger()
+    {
+        // set extremes for the calibration data
+        d.plungerMax = 0;
+        d.plungerZero = npix;
+        d.plungerMin = npix;
+    }
     // stored data (excluding the checksum)
@@ -640,7 +681,7 @@
-    void get(int &x, int &y, int &rx, int &ry) 
+    void get(int &x, int &y) 
          // disable interrupts while manipulating the shared data
@@ -711,14 +752,6 @@
          x = rawToReport(vx);
          y = rawToReport(vy);
-         // apply a small dead zone near the center
-         // if (abs(x) < 6) x = 0;
-         // if (abs(y) < 6) y = 0;
-         // report the calibrated instantaneous acceleration in rx,ry
-         rx = int(round((ax - cx_)*JOYMAX));
-         ry = int(round((ay - cy_)*JOYMAX));
          if (x != 0 || y != 0)        
              printf("%f %f %d %d %f\r\n", vx, vy, x, y, dt);
@@ -874,22 +907,6 @@
     // check for valid flash
     bool flash_valid = flash->valid();
-    // Number of pixels we read from the sensor on each frame.  This can be
-    // less than the physical pixel count if desired; we'll read every nth
-    // piexl if so.  E.g., with a 1280-pixel physical sensor, if npix is 320,
-    // we'll read every 4th pixel.  It takes time to read each pixel, so the
-    // fewer pixels we read, the higher the refresh rate we can achieve.
-    // It's therefore better not to read more pixels than we have to.
-    //
-    // VP seems to have an internal resolution in the 8-bit range, so there's
-    // no apparent benefit to reading more than 128-256 pixels when using VP.
-    // Empirically, 160 pixels seems about right.  The overall travel of a
-    // standard pinball plunger is about 3", so 160 pixels gives us resolution
-    // of about 1/50".  This seems to take full advantage of VP's modeling
-    // ability, and is probably also more precise than a human player's
-    // perception of the plunger position.
-    const int npix = 160;
     // if the flash is valid, load it; otherwise initialize to defaults
     if (flash_valid) {
         memcpy(&cfg, flash, sizeof(cfg));
@@ -918,7 +935,6 @@
     // plunger calibration button debounce timer
     Timer calBtnTimer;
-    int calBtnDownTime = 0;
     int calBtnLit = false;
     // Calibration button state:
@@ -957,10 +973,16 @@
     // so when we detect the start of this motion, we immediately tell VP
     // to return the plunger to rest, then we monitor the real plunger 
     // until it atcually stops.
-    bool firing = false;
+    int firing = 0;
     // start the first CCD integration cycle
+    // Device status.  We report this on each update so that the host config
+    // tool can detect our current settings.  This is a bit mask consisting
+    // of these bits:
+    //    0x01  -> plunger sensor enabled
+    uint16_t statusFlags = (cfg.d.ccdEnabled ? 0x01 : 0x00);
     // we're all set up - now just loop, processing sensor reports and 
     // host requests
@@ -1009,7 +1031,7 @@
                     // message type.
                     if (data[1] == 1)
-                        // Set Configuration:
+                        // 1 = Set Configuration:
                         //     data[2] = LedWiz unit number (0x00 to 0x0f)
                         //     data[3] = feature enable bit mask:
                         //               0x01 = enable CCD
@@ -1022,9 +1044,26 @@
                         cfg.d.ledWizUnitNo = newUnitNo;
                         cfg.d.ccdEnabled = data[3] & 0x01;
+                        // update the status flags
+                        statusFlags = (statusFlags & ~0x01) | (data[3] & 0x01);
+                        // if the ccd is no longer enabled, use 0 for z reports
+                        if (!cfg.d.ccdEnabled)
+                            z = 0;
                         // save the configuration
               , flash_addr);
+                    else if (data[1] == 2)
+                    {
+                        // 2 = Calibrate plunger
+                        // (No parameters)
+                        // enter calibration mode
+                        calBtnState = 3;
+                        calBtnTimer.reset();
+                        cfg.resetPlunger();
+                    }
@@ -1057,38 +1096,32 @@
             case 0: 
                 // button not yet pushed - start debouncing
-                calBtnDownTime = calBtnTimer.read_ms();
                 calBtnState = 1;
             case 1:
                 // pushed, not yet debounced - if the debounce time has
                 // passed, start the hold period
-                if (calBtnTimer.read_ms() - calBtnDownTime > 50)
+                if (calBtnTimer.read_ms() > 50)
                     calBtnState = 2;
             case 2:
                 // in the hold period - if the button has been held down
                 // for the entire hold period, move to calibration mode
-                if (calBtnTimer.read_ms() - calBtnDownTime > 2050)
+                if (calBtnTimer.read_ms() > 2050)
                     // enter calibration mode
                     calBtnState = 3;
-                    // set extremes for the calibration data, so that the actual
-                    // values we read will set new high/low water marks on the fly
-                    cfg.d.plungerMax = 0;
-                    cfg.d.plungerZero = npix;
-                    cfg.d.plungerMin = npix;
+                    calBtnTimer.reset();
+                    cfg.resetPlunger();
             case 3:
-                // Already in calibration mode - pushing the button in this
-                // state doesn't change the current state, but we won't leave
-                // this state as long as it's held down.  We can simply do
-                // nothing here.
+                // Already in calibration mode - pushing the button here
+                // doesn't change the current state, but we won't leave this
+                // state as long as it's held down.  So nothing changes here.
@@ -1101,8 +1134,7 @@
             // Otherwise, return to the base state without saving anything.
             // If the button is released before we make it to calibration
             // mode, it simply cancels the attempt.
-            if (calBtnState == 3
-                && calBtnTimer.read_ms() - calBtnDownTime > 17500)
+            if (calBtnState == 3 && calBtnTimer.read_ms() > 15000)
                 // exit calibration mode
                 calBtnState = 0;
@@ -1127,7 +1159,7 @@
         case 2:
             // in the hold period - flash the light
-            newCalBtnLit = (((calBtnTimer.read_ms() - calBtnDownTime)/250) & 1);
+            newCalBtnLit = ((calBtnTimer.read_ms()/250) & 1);
         case 3:
@@ -1150,13 +1182,13 @@
                 calBtnLed = 1;
                 ledR = 1;
                 ledG = 1;
-                ledB = 1;
+                ledB = 0;
             else {
                 calBtnLed = 0;
                 ledR = 1;
                 ledG = 1;
-                ledB = 0;
+                ledB = 1;
@@ -1246,14 +1278,34 @@
             // is complete, allowing VP to carry out the firing motion using
             // its internal model plunger rather than trying to track the
             // intermediate positions of the mechanical plunger throughout
-            // the firing motion.  This has several benefits.  First is that 
-            // our readings aren't very accurate during rapid movement,
-            // because we get too much motion blur.  Second is that the
-            // event approach allows VP to simulate the plunger motion
-            // according to each table's particular plunger settings.
-            // Different tables have different plunger strengths and speeds,
-            // so we want to defer to the model for the physics of the firing
-            // motion within each simulation.
+            // the firing motion.  This is essential because the firing
+            // motion is too fast for us to track - in the time it takes us
+            // to read one frame, the plunger can make it all the way to the
+            // zero position and bounce back halfway.  Fortunately, the range
+            // of motions for the plunger is limited, so if we see any rapid
+            // change of position toward the rest position, it's reasonably
+            // safe to interpret it as a firing event.  
+            //
+            // This isn't foolproof.  The user can trick us by doing a 
+            // controlled rapid forward push but stopping short of the rest 
+            // position.  We'll misinterpret that as a firing event.  But 
+            // that's not a natural motion that a user would make with a
+            // plunger, so it's probably an acceptable false positive.
+            //
+            // Possible future enhancement: we could add a second physical
+            // sensor that detects when the plunger reaches the zero position
+            // and asserts an interrupt.  In the interrupt handler, set a
+            // flag indicating the zero position signal.  On each scan of
+            // the CCD, also check that flag; if it's set, enter firing
+            // event mode just as we do now.  The key here is that the
+            // secondary sensor would have to be something much faster
+            // than our CCD scan - it would have to react on, say, the
+            // millisecond time scale.  A simple mechanical switch or a
+            // proximity sensor could work.  This would let us detect
+            // with certainty when the plunger physically fires, eliminating
+            // the case where the use can fool us with motion that's fast
+            // enough to look like a release but doesn't actually reach the
+            // starting position.
             // To detremine when a firing even occurs, we watch for rapid
             // motion from a retracted position towards the rest position -
@@ -1264,12 +1316,38 @@
             // position, and then suspend reports until the mechanical
             // readings indicate that the plunger has come to rest (indicated
             // by several readings in a row at roughly the same position).
-            // Check to see if plunger firing is in progress.  If not, check
-            // to see if it looks like we just started firing.
-            const int restTol = JOYMAX/npix * 4;
-            const int fireTol = JOYMAX/npix * 12;
-            if (firing)
+            //
+            // Tolerance for firing is 1/3 of the current pull distance, or
+            // about 1/2", whichever is greater.  Making this value too small
+            // makes for too many false positives.  Empirically, 1/4" is too
+            // twitchy, so set a floor at about 1/2".  But we can be less
+            // sensitive the further back the plunger is pulled, since even
+            // a long pull will snap back quickly.  Note that JOYMAX always
+            // corresponds to about 3", no matter how many pixels we're
+            // reading, since the physical sensor is about 3" long; so we
+            // factor out the pixel count calculate (approximate) physical
+            // distances based on the normalized axis range.
+            // 
+            // Firing pattern: when firing, don't simply report a solid 0,
+            // but instead report a series of pseudo-bouces.  This looks
+            // more realistic, beacause the real plunger is also bouncing
+            // around during this time.  To get maximum firing power in
+            // the simulation, though, our pseudo-bounces are tiny cmopared
+            // to the real thing.
+            const int restTol = JOYMAX/24;
+            int fireTol = z/3 > JOYMAX/6 ? z/3 : JOYMAX/6;
+            static const int firePattern[] = { 
+                -JOYMAX/12, -JOYMAX/12, -JOYMAX/12, 
+                0, 0, 0,
+                JOYMAX/16, JOYMAX/16, JOYMAX/16,
+                0, 0, 0,
+                -JOYMAX/20, -JOYMAX/20, -JOYMAX/20,
+                0, 0, 0, 
+                JOYMAX/24, JOYMAX/24, JOYMAX/24,
+                0, 0, 0,
+                -JOYMAX/30, -JOYMAX/30, -JOYMAX/30 
+            };
+            if (firing != 0)
                 // Firing in progress - we've already told VP to send its
                 // model plunger all the way back to the rest position, so
@@ -1278,11 +1356,23 @@
                 if (abs(z0 - z2) < restTol && abs(znew - z2) < restTol)
                     // the plunger is back at rest - firing is done
-                    firing = false;
+                    firing = 0;
                     // resume normal reporting
                     z = z2;
+                else if (firing < countof(firePattern))
+                {
+                    // firing - report the next position in the pseudo-bounce 
+                    // pattern
+                    z = firePattern[firing++];
+                }
+                else
+                {
+                    // firing, out of pseudo-bounce items - just report the
+                    // rest position
+                    z = 0;
+                }
             else if (z0 < z2 && z1 < z2 && znew < z2
                      && (z0 < z2 - fireTol 
@@ -1305,8 +1395,10 @@
                 // virtual plunger, rather than imposing the actual
                 // mechanical charateristics of the physical plunger on
                 // every table.
-                firing = true;
-                z = 0;
+                firing = 1;
+                // report the first firing pattern position
+                z = firePattern[0];
@@ -1320,10 +1412,16 @@
             z1 = z0;
             z0 = znew;
+        else
+        {
+            // plunger disabled - pause 10ms to throttle updates to a
+            // reasonable pace
+            wait_ms(10);
+        }
         // read the accelerometer
-        int xa, ya, rxa, rya;
-        accel.get(xa, ya, rxa, rya);
+        int xa, ya;
+        accel.get(xa, ya);
         // confine the results to our joystick axis range
         if (xa < -JOYMAX) xa = -JOYMAX;
@@ -1342,7 +1440,7 @@
         // arrangement of our nominal axes aligns with VP's standard
         // setting, so that we can configure VP with X Axis = X on the
         // joystick and Y Axis = Y on the joystick.
-        js.update(y, x, z, rxa, rya, 0);
+        js.update(y, x, z, 0, statusFlags);
         if (x != 0 || y != 0)