Mike R / Mbed 2 deprecated Pinscape_Controller_V2

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 mechanical plunger, button inputs, and feedback device control.

In case you haven't heard of the idea 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 show the backglass artwork. Some cabs also include a third monitor to simulate the DMD (Dot Matrix Display) used for scoring on 1990s machines, or even an original plasma DMD. A computer (usually a Windows PC) 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 trim hardware.

It's possible to buy a pre-built virtual pinball machine, but it also makes a great 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 vpforums.org. Also visit my Pinscape Resources page for more about this project and other virtual pinball projects I'm working on.

Downloads

• 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.

Documentation

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 potentiometer (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 mouser.com 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 Aliexpress.com 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 KL25Z can only run one firmware program at a time, so if you install the Pinscape firmware on your KL25Z, it will replace and erase your existing VirtuaPin proprietary firmware. If you do this, the only way to restore your VirtuaPin firmware is to physically ship the KL25Z back to VirtuaPin and ask them to re-flash it. They don't allow you to do this at home, and they don't even allow you to back up your firmware, since they want to protect their proprietary software from copying. For all of these reasons, if you want to run the Pinscape software, I strongly recommend that you buy a "blank" retail KL25Z to use with Pinscape. They only cost about $15 and are available at several online retailers, including Amazon, Mouser, and eBay. The blank retail boards don't come with any proprietary firmware pre-installed, so installing Pinscape won't delete anything that you paid extra for.

With those warnings in mind, if you're absolutely sure that you don't mind permanently erasing your VirtuaPin firmware, it is at least possible to use Pinscape as a replacement for the VirtuaPin firmware. Pinscape uses the same button wiring conventions as the VirtuaPin setup, so you can keep your buttons (although you'll have to update the GPIO pin mappings in the Config Tool to match your physical wiring). As of the June, 2021 firmware, the Vishay VCNL4010 plunger sensor that comes with the VirtuaPin v3 plunger kit is supported, so you can also keep your plunger, if you have that chip. (You should check to be sure that's the sensor chip you have before committing to this route, if keeping the plunger sensor is important to you. The older VirtuaPin plunger kits came with different IR sensors that the Pinscape software doesn't handle.)

--- a/main.cpp	Fri Oct 20 06:21:40 2017 +0000
+++ b/main.cpp	Thu Dec 14 00:20:20 2017 +0000
@@ -1312,11 +1312,12 @@
 };
 
 
-// Conversion table for 8-bit DOF level to pulse width in microseconds,
-// with gamma correction.  We could use the layered gamma output on top 
-// of the regular LwPwmOut class for this, but we get better precision
-// with a dedicated table, because we apply gamma correction to the
-// 32-bit microsecond values rather than the 8-bit DOF levels.
+// Conversion table for 8-bit DOF level to pulse width, with gamma correction
+// pre-calculated.  The values are normalized duty cycles from 0.0 to 1.0.
+// Note that we could use the layered gamma output on top of the regular 
+// LwPwmOut class for this instead of a separate table, but we get much better 
+// precision with a dedicated table, because we apply gamma correction to the
+// actual duty cycle values (as 'float') rather than the 8-bit DOF values.
 static const float dof_to_gamma_pwm[] = {
     0.000000f, 0.000000f, 0.000001f, 0.000004f, 0.000009f, 0.000017f, 0.000028f, 0.000042f,
     0.000062f, 0.000086f, 0.000115f, 0.000151f, 0.000192f, 0.000240f, 0.000296f, 0.000359f,
@@ -1360,43 +1361,60 @@
 // The value register controls the duty cycle, so it's what you have to write
 // if you want to update the brightness of an output.
 //
-// Our solution is to simply repeat all PWM updates periodically.  If a write
-// is lost on one cycle, it'll eventually be applied on a subseuqent periodic
-// update.  For low overhead, we do these repeat updates periodically during
-// the main loop.
-//
-// The mbed library has its own solution to this bug, but it creates a 
-// separate problem of its own.  The mbed solution is to write the value
-// register immediately, and then also reset the "count" register in the 
-// TPM unit containing the output.  The count reset truncates the current
-// PWM cycle, which avoids the hardware problem with more than one write per
-// cycle.  The problem is that the truncated cycle causes visible flicker if
-// the output is connected to an LED.  This is particularly noticeable during
-// fades, when we're updating the value register repeatedly and rapidly: an
-// attempt to fade from fully on to fully off causes rapid fluttering and 
-// flashing rather than a smooth brightness fade.
-//
-// The hardware bug is a case of good intentions gone bad.  The hardware is
-// *supposed* to make it easy for software to avoid glitching during PWM
-// updates, by providing a staging register in front of the real value
-// register.  The software actually writes to the staging register, which
-// holds updates until the end of the cycle, at which point the hardware
-// automatically moves the value from the staging register into the real
-// register.  This ensures that the real register is always updated exactly
-// at a cycle boundary, which in turn ensures that there's no flicker when
-// values are updated.  A great design - except that it doesn't quite work.
-// The problem is that the staging register actually seems to be implemented
-// as a one-element FIFO in "stop when full" mode.  That is, when you write
-// the FIFO, it becomes full.  When the cycle ends and the hardware reads it
-// to move the staged value into the real register, the FIFO becomes empty.
-// But if you try to write the FIFO twice before the hardware reads it and
-// empties it, the second write fails, leaving the first value in the queue.
-// There doesn't seem to be any way to clear the FIFO from software, so you
-// just have to wait for the cycle to end before writing another update.
-// That more or less defeats the purpose of the staging register, whose whole
-// point is to free software from worrying about timing considerations with
-// updates.  It frees us of the need to align our timing on cycle boundaries,
-// but it leaves us with the need to limit writes to once per cycle.
+// The symptom of the problem, if it's not worked around somehow, is that 
+// an output will get "stuck" due to a missed write.  This is especially
+// noticeable during a series of updates such as a fade.  If the last
+// couple of updates in a fade are lost, the output will get stuck at some
+// value above or below the desired final value.  The stuck setting will
+// persist until the output is deliberately changed again later.
+//
+// Our solution:  Simply repeat all PWM updates periodically.  This way, any
+// lost write will *eventually* take hold on one of the repeats.  Repeats of
+// the same value won't change anything and thus won't be noticeable.  We do
+// these periodic updates during the main loop, which makes them very low 
+// overhead (there's no interrupt overhead; we just do them when convenient 
+// in the main loop), and also makes them very frequent.  The frequency 
+// is crucial because it ensures that updates will never be lost for long 
+// enough to become noticeable.
+//
+// The mbed library has its own, different solution to this bug, but the
+// mbed solution isn't really a solution at all because it creates a separate 
+// problem of its own.  The mbed approach is reset the TPM "count" register
+// on every value register write.   The count reset truncates the current
+// PWM cycle, which bypasses the hardware problem.  Remember, the hardware
+// problem is that you can only write once per cycle; the mbed "solution" gets
+// around that by making sure the cycle ends immediately after the write.
+// The problem with this approach is that the truncated cycle causes visible 
+// flicker if the output is connected to an LED.  This is particularly 
+// noticeable during fades, when we're updating the value register repeatedly 
+// and rapidly: an attempt to fade from fully on to fully off causes rapid 
+// fluttering and flashing rather than a smooth brightness fade.  That's why
+// I had to come up with something different - the mbed solution just trades
+// one annoying bug for another that's just as bad.
+//
+// The hardware bug, by the way, is a case of good intentions gone bad.  
+// The whole point of the staging register is to make things easier for
+// us software writers.  In most PWM hardware, software has to coordinate
+// with the PWM duty cycle when updating registers to avoid a glitch that
+// you'd get by scribbling to the duty cycle register mid-cycle.  The
+// staging register solves this by letting the software write an update at
+// any time, knowing that the hardware will apply the update at exactly the
+// end of the cycle, ensuring glitch-free updates.  It's a great design,
+// except that it doesn't quite work.  The problem is that they implemented
+// this clever staging register as a one-element FIFO that refuses any more
+// writes when full.  That is, writing a value to the FIFO fills it; once
+// full, it ignores writes until it gets emptied out.  How's it emptied out?
+// By the hardware moving the staged value to the real register.  Sadly, they
+// didn't provide any way for the software to clear the register, and no way
+// to even tell that it's full.  So we don't have glitches on write, but we're
+// back to the original problem that the software has to be aware of the PWM
+// cycle timing, because the only way for the software to know that a write
+// actually worked is to know that it's been at least one PWM cycle since the
+// last write.  That largely defeats the whole purpose of the staging register,
+// since the whole point was to free software writers of these timing
+// considerations.  It's still an improvement over no staging register at
+// all, since we at least don't have to worry about glitches, but it leaves
+// us with this somewhat similar hassle.
 //
 // So here we have our list of PWM outputs that need to be polled for updates.
 // The KL25Z hardware only has 10 PWM channels, so we only need a fixed set
@@ -1997,14 +2015,13 @@
 }
 
 // Turn off all outputs and restore everything to the default LedWiz
-// state.  This sets outputs #1-32 to LedWiz profile value 48 (full
-// brightness) and switch state Off, sets all extended outputs (#33
-// and above) to zero brightness, and sets the LedWiz flash rate to 2.
-// This effectively restores the power-on conditions.
+// state.  This sets all outputs to LedWiz profile value 48 (full
+// brightness) and switch state Off, and sets the LedWiz flash rate 
+// to 2.  This effectively restores the power-on conditions.
 //
 void allOutputsOff()
 {
-    // reset all LedWiz outputs to OFF/48
+    // reset all outputs to OFF/48
     for (int i = 0 ; i < numOutputs ; ++i)
     {
         outLevel[i] = 0;
@@ -5690,6 +5707,7 @@
                 true,               // we support sbx/pbx extensions
                 true,               // we support the new accelerometer settings
                 true,               // we support the "flash write ok" status bit in joystick reports
+                true,               // we support the configurable joystick report timing features
                 mallocBytesFree()); // remaining memory size
             break;
             
@@ -6106,27 +6124,41 @@
     // we're now connected to the host
     connected = true;
     
-    // Last report timer for the joytick interface.  We use this timer to
-    // throttle the report rate to a pace that's suitable for VP.  Without
-    // any artificial delays, we could generate data to send on the joystick
-    // interface on every loop iteration.  The loop iteration time depends
-    // on which devices are attached, since most of the work in our main 
-    // loop is simply polling our devices.  For typical setups, the loop
-    // time ranges from about 0.25ms to 2.5ms; the biggest factor is the
-    // plunger sensor.  But VP polls for input about every 10ms, so there's 
-    // no benefit in sending data faster than that, and there's some harm,
-    // in that it creates USB overhead (both on the wire and on the host 
-    // CPU).  We therefore use this timer to pace our reports to roughly
-    // the VP input polling rate.  Note that there's no way to actually
-    // synchronize with VP's polling, but there's also no need to, as the
-    // input model is designed to reflect the overall current state at any
-    // given time rather than events or deltas.  If VP polls twice between
-    // two updates, it simply sees no state change; if we send two updates
-    // between VP polls, VP simply sees the latest state when it does get
-    // around to polling.
+    // Set up a timer for keeping track of how long it's been since we
+    // sent the last joystick report.  We use this to determine when it's
+    // time to send the next joystick report.  
+    //
+    // We have to use a timer for two reasons.  The first is that our main
+    // loop runs too fast (about .25ms to 2.5ms per loop, depending on the
+    // type of plunger sensor attached and other factors) for us to send
+    // joystick reports on every iteration.  We *could*, but the PC couldn't
+    // digest them at that pace.  So we need to slow down the reports to a
+    // reasonable pace.  The second is that VP has some complicated timing
+    // issues of its own, so we not only need to slow down the reports from
+    // our "natural" pace, but also time them to sync up with VP's input
+    // sampling rate as best we can.
     Timer jsReportTimer;
     jsReportTimer.start();
     
+    // Accelerometer sample "stutter" counter.  Each time we send a joystick
+    // report, we increment this counter, and check to see if it has reached 
+    // the threshold set in the configuration.  If so, we take a new 
+    // accelerometer sample and send it with the new joystick report.  It
+    // not, we don't take a new sample, but simply repeat the last sample.
+    //
+    // This lets us send joystick reports more frequently than accelerometer
+    // samples.  The point is to let us slow down accelerometer reports to
+    // a pace that matches VP's input sampling frequency, while still sending
+    // joystick button updates more frequently, so that other programs that
+    // can read input faster will see button changes with less latency.
+    int jsAccelStutterCounter = 0;
+    
+    // Last accelerometer report, in joystick units.  We normally report the 
+    // acceleromter reading via the joystick X and Y axes, per the VP 
+    // convention.  We can alternatively report in the RX and RY axes; this
+    // can be set in the configuration.
+    int x = 0, y = 0;
+    
     // Time since we successfully sent a USB report.  This is a hacky 
     // workaround to deal with any remaining sporadic problems in the USB 
     // stack.  I've been trying to bulletproof the USB code over time to 
@@ -6170,10 +6202,6 @@
     Accel accel(MMA8451_SCL_PIN, MMA8451_SDA_PIN, MMA8451_I2C_ADDRESS, 
         MMA8451_INT_PIN, cfg.accel.range, cfg.accel.autoCenterTime);
        
-    // last accelerometer report, in joystick units (we report the nudge
-    // acceleration via the joystick x & y axes, per the VP convention)
-    int x = 0, y = 0;
-    
     // initialize the plunger sensor
     plungerSensor->init();
     
@@ -6415,21 +6443,30 @@
         // the new report.  VP only polls for input in 10ms intervals, so
         // there's no benefit in sending reports more frequently than this.
         // More frequent reporting would only add USB I/O overhead.
-        if (cfg.joystickEnabled && jsReportTimer.read_us() > 10000UL)
+        if (cfg.joystickEnabled && jsReportTimer.read_us() > cfg.jsReportInterval_us)
         {
-            // read the accelerometer
-            int xa, ya;
-            accel.get(xa, ya);
+            // Increment the "stutter" counter.  If it has reached the
+            // stutter threshold, read a new accelerometer sample.  If 
+            // not, repeat the last sample.
+            if (++jsAccelStutterCounter >= cfg.accel.stutter)
+            {
+                // read the accelerometer
+                int xa, ya;
+                accel.get(xa, ya);
             
-            // confine the results to our joystick axis range
-            if (xa < -JOYMAX) xa = -JOYMAX;
-            if (xa > JOYMAX) xa = JOYMAX;
-            if (ya < -JOYMAX) ya = -JOYMAX;
-            if (ya > JOYMAX) ya = JOYMAX;
-            
-            // store the updated accelerometer coordinates
-            x = xa;
-            y = ya;
+                // confine the results to our joystick axis range
+                if (xa < -JOYMAX) xa = -JOYMAX;
+                if (xa > JOYMAX) xa = JOYMAX;
+                if (ya < -JOYMAX) ya = -JOYMAX;
+                if (ya > JOYMAX) ya = JOYMAX;
+                
+                // store the updated accelerometer coordinates
+                x = xa;
+                y = ya;
+                
+                // reset the stutter counter
+                jsAccelStutterCounter = 0;
+            }
             
             // Report the current plunger position unless the plunger is
             // disabled, or the ZB Launch Ball signal is on.  In either of
@@ -6438,14 +6475,14 @@
             // tells us that the table has a Launch Ball button instead of
             // a traditional plunger, so we don't want to confuse VP with
             // regular plunger inputs.
-            int z = plungerReader.getPosition();
-            int zrep = (!cfg.plunger.enabled || zbLaunchOn ? 0 : z);
+            int zActual = plungerReader.getPosition();
+            int zReported = (!cfg.plunger.enabled || zbLaunchOn ? 0 : zActual);
             
             // rotate X and Y according to the device orientation in the cabinet
             accelRotate(x, y);
 
             // send the joystick report
-            jsOK = js.update(x, y, zrep, jsButtons, statusFlags);
+            jsOK = js.update(x, y, zReported, jsButtons, statusFlags);
             
             // we've just started a new report interval, so reset the timer
             jsReportTimer.reset();