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.)

diff -r 42dc75fbe623 -r 8ed709f455c0 main.cpp
--- a/main.cpp	Mon Feb 22 06:57:59 2021 +0000
+++ b/main.cpp	Thu Apr 29 19:56:49 2021 +0000
@@ -306,6 +306,13 @@
 
 // --------------------------------------------------------------------------
 // 
+// placement new
+//
+void* operator new (size_t, void *p) { return p; }
+
+
+// --------------------------------------------------------------------------
+// 
 // OpenSDA module identifier.  This is for the benefit of the Windows
 // configuration tool.  When the config tool installs a .bin file onto
 // the KL25Z, it will first find the sentinel string within the .bin file,
@@ -4119,9 +4126,9 @@
 // I2C address of the accelerometer (this is a constant of the KL25Z)
 const int MMA8451_I2C_ADDRESS = (0x1d<<1);
 
-// SCL and SDA pins for the accelerometer (constant for the KL25Z)
-#define MMA8451_SCL_PIN   PTE25
-#define MMA8451_SDA_PIN   PTE24
+// I2C pins for the accelerometer (constant for the KL25Z)
+#define MMA8451_SDA_PIN   PTE25
+#define MMA8451_SCL_PIN   PTE24
 
 // Digital in pin to use for the accelerometer interrupt.  For the KL25Z,
 // this can be either PTA14 or PTA15, since those are the pins physically
@@ -4164,18 +4171,13 @@
 class Accel
 {
 public:
-    Accel(PinName sda, PinName scl, int i2cAddr, PinName irqPin, 
-        int range, int autoCenterMode)
-        : mma_(sda, scl, i2cAddr)        
+    Accel(const Config &cfg) : mma_(MMA8451_SDA_PIN, MMA8451_SCL_PIN, MMA8451_I2C_ADDRESS)        
     {
-        // remember the interrupt pin assignment
-        irqPin_ = irqPin;
-        
         // remember the range
-        range_ = range;
+        range_ = cfg.accel.range;
         
         // set the auto-centering mode
-        setAutoCenterMode(autoCenterMode);
+        setAutoCenterMode(cfg.accel.autoCenterTime);
         
         // no manual centering request has been received
         manualCenterRequest_ = false;
@@ -4184,6 +4186,62 @@
         reset();
     }
     
+    // Do a full reset of the object.  This tries to clear the I2C
+    // bus, and then re-creates the Accel object in place, running
+    // through all of the constructors again.  This is only a "soft"
+    // reset, since the KL25Z doesn't give us any way to do a power
+    // cycle on the MMA8451Q from software - its power connection is
+    // hardwired to the KL25Z's main board power connection, so the
+    // only way to power cycle the accelerometer is to power cycle
+    // the whole board.
+    //
+    // We use this to try to reset the accelerometer if it stops
+    // sending us new samples.  I've received a few reports from
+    // people who say their accelerometers seem to stop working even
+    // though the rest of the firmware is still functioning normally,
+    // which suggests that there's either a problem in the Accel class
+    // itself, or that the MMA8451Q can get into a non-responsive state
+    // under some circumstances.  Since the reports have been extremely
+    // rare and isolated, and since I've never myself seen this happen
+    // on any of the multiple KL25Z boards I've tested with (even after
+    // leaving them running for days at a time), my best guess is that
+    // it's actually a fault in the MMA8451Q.  The fact that everyone
+    // who's experienced the accelerometer freeze says that the rest of
+    // the firwmare is still working supports this hypothesis - given
+    // that the firmware is single-threaded, it seems unlikely that a
+    // "crash" of some kind in the accelerometer code wouldn't crash
+    // the firmware as a whole.  This soft reset code is an attempt to
+    // recover from a scenario where the MMA8451Q hardware is still
+    // functioning properly, but its internal state machine is somehow
+    // out of sync with the host in such a way that it can no longer
+    // send us samples - either its I2C state machine is stuck in the
+    // middle of a transaction, or its sample processing state machine
+    // is no longer taking samples.  The soft reset doesn't have any
+    // hope of rebooting the chip if the freeze is due to some kind
+    // of hardware fault, because our only connection to the chip is
+    // the I2C bus, and there's no reason to think its I2C state
+    // machine would even be running in the event of a hardware fault.
+    // Hopefully we can find out which it is by testing this fix on
+    // boards where the problem is known to have occurred, since it
+    // seems to be readily repeatable for the people who experience
+    // it at all.
+    static void softReset(Accel *accel, const Config &config)
+    {
+        // save the current centering position, so that the user
+        // doesn't see a jump across the reset
+        int cx = accel->cx_, cy = accel->cy_;
+        
+        // try to reset the I2C bus, in case that's 
+        accel->clear_i2c();
+        
+        // re-construct the Accel object
+        new (accel) Accel(config);
+
+        // restore the center point
+        accel->cx_ = cx;
+        accel->cy_ = cy; 
+    }
+    
     // Request manual centering.  This applies the trailing average
     // of recent measurements and applies it as the new center point
     // as soon as we have enough data.
@@ -4220,6 +4278,81 @@
         }
     }
     
+    // Clear the I2C bus for the MMA8451Q.  This seems necessary some of the time
+    // for reasons that aren't clear to me.  Doing a hard power cycle has the same
+    // effect, but when we do a soft reset, the hardware sometimes seems to leave
+    // the MMA's SDA line stuck low.  Presumably, the MMA8451Q's internal state
+    // machine is still in the middle of an I2C transaction, and it expects the
+    // host to clock in/out the rest of the bits for the transaction.  Forcing a
+    // series of clock pulses through SCL is the standard remedy for this type
+    // of situation, since it should force the state machine to the end of the
+    // I2C state it's stuck in so that it's ready to start a new transaction.
+    // This really shouldn't be necessary, because the mbed library I2C code that
+    // we're using in the MMA8451Q driver appears to do the same thing when it
+    // sets up the I2C pins, but it should at least be harmless.  What we really
+    // need is a way to power-cycle the MMA8451Q, but the KL25Z simply isn't
+    // wired to do that from software; the only way is to power-cycle the whole
+    // board.
+    // 
+    // If the accelerometer does get stuck, and a software reboot doesn't reset
+    // it, the only workaround is to manually power cycle the whole KL25Z by 
+    // unplugging both of its USB connections.
+    //
+    // The entire Accel object must be re-constructed after calling this,
+    // because this reconfigures the I2C SDA/SCL pins as plain digital in/out
+    // pins.  They have to be reconfigured as I2C pins again by the I2C
+    // constructor after this is called.
+    static bool clear_i2c()
+    {
+        // set up both pints as input pins
+        DigitalInOut pin_sda(MMA8451_SDA_PIN, PIN_INPUT, PullNone, 1);
+        DigitalInOut pin_scl(MMA8451_SCL_PIN, PIN_INPUT, PullNone, 1);
+
+        // if SCL is being held low, the bus is locked by another device;
+        // wait a couple of milliseconds and then give up
+        Timer t;
+        t.start();
+        while (pin_scl == 0 && t.read_us() < 2000) { }
+        if (pin_scl == 0)
+            return false;
+
+        // if SDA and SCL are both high, the bus is free
+        if (pin_sda == 1)
+            return true;
+
+        // Send a series of clock pulses to try to knock the device out
+        // of whatever I2C transaction it thinks it's in the middle of.
+        // 9 pulses should be sufficient for a device with byte commands,
+        // but do some extra for good measure, in case it's in some kind
+        // of multi-byte transaction.
+        pin_scl.mode(PullNone);
+        pin_scl.output();
+        for (int count = 0; count < 35; count++) 
+        {
+            pin_scl.mode(PullNone);
+            pin_scl = 0;
+            wait_us(5);
+            pin_scl.mode(PullUp);
+            pin_scl = 1;
+            wait_us(5);
+        }
+
+        // Send Stop
+        pin_sda.output();
+        pin_sda = 0;
+        wait_us(5);
+        pin_scl = 1;
+        wait_us(5);
+        pin_sda = 1;
+        wait_us(5);
+
+        // confirm that both SDA and SCL are now high, indicating that
+        // the bus is free
+        pin_sda.input();
+        pin_scl.input();
+        return (pin_scl != 0 && pin_sda != 0);
+    }
+
     void reset()
     {
         // clear the center point
@@ -4244,16 +4377,34 @@
         
         // read the current registers to clear the data ready flag
         mma_.getAccXYZ(ax_, ay_, az_);
+        
+        // start the FIFO timer
+        fifoTimer.reset();
+        fifoTimer.start();
+        tLastSample = tLastChangedSample = fifoTimer.read_us();
     }
     
-    void poll()
+    // Poll the accelerometer.  Returns true on success, false if the
+    // device appears to be wedged (because we haven't received a unique
+    // sample in a long time).  The caller can try re-creating the Accel
+    // object if the device is wedged.
+    bool poll()
     {
         // read samples until we clear the FIFO
         while (mma_.getFIFOCount() != 0)
         {
+            // read the raw data
             int x, y, z;
             mma_.getAccXYZ(x, y, z);
             
+            // note the time
+            tLastSample = fifoTimer.read_us();
+            
+            // note if this sample differs from the last one, to see if
+            // the accelerometer appears to be stuck
+            if (x != ax_ || y != ay_ || z != az_)
+                tLastChangedSample = tLastSample;
+            
             // add the new reading to the running total for averaging
             xSum_ += (x - cx_);
             ySum_ += (y - cy_);
@@ -4264,8 +4415,59 @@
             ay_ = y;
             az_ = z;
         }
+        
+        // If we haven't seen a new sample in a while, the device
+        // might be stuck.  Some people have observed an apparent
+        // freeze in the accelerometer readings even while the
+        // pluger and key inputs continue working, which seems
+        // like it must be due to something stuck on the MMA8451Q.
+        // The caller can try a software reset in that case, by
+        // re-creating the Accel object.  That will go through
+        // all of the I2C and MMA8451Q intialization code again
+        // to try to get things back to a good state.
+        //
+        // We poll about every 2.5ms (or more often, depending on
+        // the plunger sensor type), and we have the accelerometer
+        // set to generate samples at 800 Hz = every 1.25ms, so it
+        // would definitely indicate trouble if the last samples
+        // from the device are older than 5ms.  As for *unique*
+        // samples, that's a harder call, since it depends on how
+        // much background noise there is.  Given the sensitivity
+        // of the device, though, my experience is that nearly
+        // every sample will have at least one bit of difference
+        // from the last, so it's unlikely to see more than a few
+        // identical samples in a row, and extremely unlikely to
+        // see, say, 10 or 20 consecutive identical readings.  To
+        // be conservative, we'll time out the existence of a
+        // reading at 100ms, and unique readings at 2s.  This
+        // should reset a non-responsive device well before the
+        // freeze becomes apparent to the user (unless they're
+        // deliberately looking for it), but should also ensure
+        // that we don't reset unnecessarily - 2s represents 1600
+        // consecutive identical samples, and I think the odds of
+        // that happening for real are practically zero, barring
+        // some kind of test bed with extreme vibration suppression.
+        uint32_t tNow = fifoTimer.read_us();
+        if (static_cast<uint32_t>(tNow - tLastSample) > 100000  // 100 ms
+            || static_cast<uint32_t>(tNow - tLastChangedSample) > 2000000) // 2 seconds
+        {
+            // appears to be wedged
+            return false;
+        }
+        
+        // okay
+        return true;
     }
-
+    
+    // timer, for monitoring incoming FIFO samples
+    Timer fifoTimer;
+    
+    // time of last sample from FIFO
+    uint32_t tLastSample;
+    
+    // time of last *different* sample from FIFO
+    uint32_t tLastChangedSample;
+    
     void get(int &x, int &y) 
     {
         // read the shared data and store locally for calculations
@@ -4407,7 +4609,7 @@
     
     // atuo-centering timer
     Timer tCenter_;
-
+    
     // Auto-centering history.  This is a separate history list that
     // records results spaced out sparsely over time, so that we can
     // watch for long-lasting periods of rest.  When we observe nearly
@@ -4423,43 +4625,8 @@
     uint8_t iAccPrv_, nAccPrv_;
     static const uint8_t maxAccPrv = 5;
     AccHist accPrv_[maxAccPrv];
-    
-    // interurupt pin name
-    PinName irqPin_;
 };
 
-// ---------------------------------------------------------------------------
-//
-// Clear the I2C bus for the MMA8451Q.  This seems necessary some of the time
-// for reasons that aren't clear to me.  Doing a hard power cycle has the same
-// effect, but when we do a soft reset, the hardware sometimes seems to leave
-// the MMA's SDA line stuck low.  Forcing a series of 9 clock pulses through
-// the SCL line is supposed to clear this condition.  I'm not convinced this
-// actually works with the way this component is wired on the KL25Z, but it
-// seems harmless, so we'll do it on reset in case it does some good.  What
-// we really seem to need is a way to power cycle the MMA8451Q if it ever 
-// gets stuck, but this is simply not possible in software on the KL25Z. 
-// 
-// If the accelerometer does get stuck, and a software reboot doesn't reset
-// it, the only workaround is to manually power cycle the whole KL25Z by 
-// unplugging both of its USB connections.
-//
-void clear_i2c()
-{
-    // set up general-purpose output pins to the I2C lines
-    DigitalOut scl(MMA8451_SCL_PIN);
-    DigitalIn sda(MMA8451_SDA_PIN);
-    
-    // clock the SCL 9 times
-    for (int i = 0 ; i < 9 ; ++i)
-    {
-        scl = 1;
-        wait_us(20);
-        scl = 0;
-        wait_us(20);
-    }
-}
-
 
 // ---------------------------------------------------------------------------
 //
@@ -6534,7 +6701,7 @@
     NewPwmUnit::defaultPeriod = 0.0005f;
         
     // clear the I2C connection
-    clear_i2c();
+    Accel::clear_i2c();
     
     // Elevate GPIO pin interrupt priorities, so that they can preempt
     // other interrupts.  This is important for some external peripherals,
@@ -6745,8 +6912,7 @@
     acTimer.start();
     
     // create the accelerometer object
-    Accel accel(MMA8451_SCL_PIN, MMA8451_SDA_PIN, MMA8451_I2C_ADDRESS, 
-        MMA8451_INT_PIN, cfg.accel.range, cfg.accel.autoCenterTime);
+    Accel accel(cfg);
        
     // initialize the plunger sensor
     plungerSensor->init();
@@ -6815,7 +6981,8 @@
         LwChimeLogicOut::poll();
         
         // poll the accelerometer
-        accel.poll();
+        if (!accel.poll())
+            Accel::softReset(&accel, cfg);
             
         // Note the "effective" plunger enabled status.  This has two
         // components: the explicit "enabled" bit, and the plunger sensor