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.


17 months ago

File content as of revision 101:755f44622abc:

// Plunger Sensor Interface
// This module defines the abstract interface to the plunger sensors.
// We support several different physical sensor types, so we need a
// common interface for use in the main code.
// In case it's helpful in developing code for new sensor types, I've
// measured the maximum instantaneous speed of a plunger at .175 inches
// per millisecond, or 4.46 mm/ms.  (I measured that with an AEDR-8300;
// see that code for more details.)

#ifndef PLUNGER_H
#define PLUNGER_H

#include "config.h"

// Plunger reading with timestamp
struct PlungerReading
    // Raw sensor reading, normalied to 0x0000..0xFFFF range
    int pos;
    // Rimestamp of reading, in microseconds, relative to an arbitrary
    // zero point.  Note that a 32-bit int can only represent about 71.5
    // minutes worth of microseconds, so this value is only meaningful
    // to compute a delta from other recent readings.  As long as two
    // readings are within 71.5 minutes of each other, the time difference
    // calculated from the timestamps using 32-bit math will be correct
    // *even if a rollover occurs* between the two readings, since the
    // calculation is done mod 2^32-1.
    uint32_t t;

class PlungerSensor
    PlungerSensor(int nativeScale)
        // use the joystick scale as our native scale by default
        this->nativeScale = nativeScale;
        // figure the scaling factor
        scalingFactor = (65535UL*65536UL) / nativeScale;
        // presume no jitter filter
        jfWindow = 0;
        // initialize the jitter filter
        jfLo = jfHi = jfLast = 0;
        // presume normal orientation
        reverseOrientation = false;

    // ---------- Abstract sensor interface ----------
    // Initialize the physical sensor device.  This is called at startup
    // to set up the device for first use.
    virtual void init() { }
    // Auto-zero the plunger.  Relative sensor types, such as quadrature
    // sensors, can lose sync with the absolute position over time if they
    // ever miss any motion.  We can automatically correct for this by
    // resetting to the park position after periods of inactivity.  It's
    // usually safe to assume that the plunger is at the park position if it 
    // hasn't moved in a long time, since the spring always returns it to 
    // that position when it isn't being manipulated.  The main loop monitors
    // for motion, and calls this after a long enough time goes by without
    // seeing any movement.  Sensor types that are inherently absolute
    // (TSL1410, potentiometers) shouldn't do anything here.
    virtual void autoZero() { }

    // Is the sensor ready to take a reading?  The optical sensor requires
    // a fairly long time (2.5ms) to transfer the data for each reading, but 
    // this is done via DMA, so we can carry on other work while the transfer
    // takes place.  This lets us poll the sensor to see if it's still busy
    // working on the current reading's data transfer.
    virtual bool ready() { return true; }
    // Read the sensor position, if possible.  Returns true on success,
    // false if it wasn't possible to take a reading.  On success, fills
    // in 'r' with the current reading and timestamp and returns true.
    // Returns false if a reading couldn't be taken.
    // r.pos is set to the normalized position reading, and r.t is set to
    // the timestamp of the reading.
    // The normalized position is the sensor reading, corrected for jitter,
    // and adjusted to the abstract 0x0000..0xFFFF range.
    // The timestamp is the time the sensor reading was taken, relative to
    // an arbitrary zero point.  The arbitrary zero point makes this useful
    // only for calculating the time between readings.  Note that the 32-bit
    // timestamp rolls over about every 71 minutes, so it should only be
    // used for time differences between readings taken fairly close together.
    // In practice, the higher level code only uses this for a few consecutive
    // readings to calculate (nearly) instantaneous velocities, so the time
    // spans are only tens of milliseconds.
    // Timing requirements:  for best results, readings should be taken
    // in well under 5ms.  The release motion of the physical plunger
    // takes from 30ms to 50ms, so we need to collect samples much faster
    // than that to avoid aliasing during the bounce.
    bool read(PlungerReading &r)
        // fail if the hardware scan isn't ready
        if (!ready())
            return false;
        // get the raw reading
        if (readRaw(r))
            // adjust for orientation
            r.pos = applyOrientation(r.pos);

            // process it through the jitter filter
            r.pos = jitterFilter(r.pos);
            // adjust to the abstract scale via the scaling factor
            r.pos = uint16_t(uint32_t((scalingFactor * r.pos) + 32768) >> 16);
            // success
            return true;
            // no reading is available
            return false;

    // Get a raw plunger reading.  This gets the raw sensor reading with
    // timestamp, without jitter filtering and without any scale adjustment.
    virtual bool readRaw(PlungerReading &r) = 0;
    // Restore the saved calibration data from the configuration.  The main 
    // loop calls this at startup to let us initialize internals from the
    // saved calibration data.  This is called even if the plunger isn't 
    // calibrated, which is flagged in the config.
    virtual void restoreCalibration(Config &) { }
    // Begin calibration.  The main loop calls this when the user activates
    // calibration mode.  Sensors that work in terms of relative positions,
    // such as quadrature-based sensors, can use this to set the reference
    // point for the park position internally.
    virtual void beginCalibration(Config &) { }
    // End calibration.  The main loop calls this when calibration mode is
    // completed.
    virtual void endCalibration(Config &) { }
    // Send a sensor status report to the host, via the joystick interface.
    // This provides some common information for all sensor types, and also
    // includes a full image snapshot of the current sensor pixels for
    // imaging sensor types.
    // The default implementation here sends the common information
    // packet, with the pixel size set to 0.
    // 'flags' is a combination of bit flags:
    //   0x01  -> low-res scan (default is high res scan)
    // Low-res scan mode means that the sensor should send a scaled-down
    // image, at a reduced size determined by the sensor subtype.  The
    // default if this flag isn't set is to send the full image, at the
    // sensor's native pixel size.  The low-res version is a reduced size
    // image in the normal sense of scaling down a photo image, keeping the
    // image intact but at reduced resolution.  Note that low-res mode
    // doesn't affect the ongoing sensor operation at all.  It only applies
    // to this single pixel report.  The purpose is simply to reduce the USB 
    // transmission time for the image, to allow for a faster frame rate for 
    // displaying the sensor image in real time on the PC.  For a high-res
    // sensor like the TSL1410R, sending the full pixel array by USB takes 
    // so long that the frame rate is way below regular video rates.
    virtual void sendStatusReport(class USBJoystick &js, uint8_t flags)
        // read the current position
        int pos = 0xFFFF;
        PlungerReading r;
        if (readRaw(r))
            // adjust for reverse orientation
            r.pos = applyOrientation(r.pos);

            // success - apply the jitter filter
            pos = jitterFilter(r.pos);
        // Send the common status information, indicating 0 pixels, standard
        // sensor orientation, and zero processing time.  Non-imaging sensors 
        // usually don't have any way to detect the orientation, so assume
        // normal orientation (flag 0x01).  Also assume zero analysis time,
        // as most non-image sensors don't have to do anything CPU-intensive
        // with the raw readings (all they usually have to do is scale the
        // value to the abstract reporting range).
        js.sendPlungerStatus(0, pos, 0x01, getAvgScanTime(), 0);
        js.sendPlungerStatus2(nativeScale, jfLo, jfHi, r.pos, 0);
    // Set extra image integration time, in microseconds.  This is only 
    // meaningful for image-type sensors.  This allows the PC client to
    // manually adjust the exposure time for testing and debugging
    // purposes.
    virtual void setExtraIntegrationTime(uint32_t us) { }
    // Get the average sensor scan time in microseconds
    virtual uint32_t getAvgScanTime() = 0;
    // Apply the orientation filter.  The position is in unscaled
    // native sensor units.
    int applyOrientation(int pos)
        return (reverseOrientation ? nativeScale - pos : pos);
    // Apply the jitter filter.  The position is in unscaled native 
    // sensor units.
    int jitterFilter(int pos)
        // Check to see where the new reading is relative to the
        // current window
        if (pos < jfLo)
            // the new position is below the current window, so move
            // the window down such that the new point is at the bottom 
            // of the window
            jfLo = pos;
            jfHi = pos + jfWindow;
            // figure the new position as the centerpoint of the new window
            jfLast = pos = (jfHi + jfLo)/2;
            return pos;
        else if (pos > jfHi)
            // the new position is above the current window, so move
            // the window up such that the new point is at the top of
            // the window
            jfHi = pos;
            jfLo = pos - jfWindow;

            // figure the new position as the centerpoint of the new window
            jfLast = pos = (jfHi + jfLo)/2;
            return pos;
            // the new position is inside the current window, so repeat
            // the last reading
            return jfLast;
    // Process a configuration variable change.  'varno' is the
    // USB protocol variable number being updated; 'cfg' is the
    // updated configuration.
    virtual void onConfigChange(int varno, Config &cfg)
        switch (varno)
        case 19:
            // Plunger filters - jitter window and reverse orientation.
            setReverseOrientation((cfg.plunger.reverseOrientation & 0x01) != 0);
    // Set the jitter filter window size.  This is specified in native
    // sensor units.
    void setJitterWindow(int w)
        // set the new window size
        jfWindow = w;
        // reset the running window
        jfHi = jfLo = jfLast;
    // Set reverse orientation
    void setReverseOrientation(bool f) { reverseOrientation = f; }
    // Native scale of the device.  This is the scale used for the position
    // reading in status reports.  This lets us report the position in the
    // same units the sensor itself uses, to avoid any rounding error 
    // converting to an abstract scale.
    // The nativeScale value is the number of units in the range of raw
    // sensor readings returned from readRaw().  Raw readings thus have a
    // valid range of 0 to nativeScale-1.
    // Image edge detection sensors use the pixel size of the image, since
    // the position is determined by the pixel position of the shadow in
    // the image.  Quadrature sensors and other sensors that report the
    // distance in terms of physical distance units should use the number
    // of quanta in the approximate total plunger travel distance of 3".
    // For example, the VL6180X uses millimeter quanta, so can report
    // about 77 quanta over 3"; a quadrature sensor that reports at 1/300"
    // intervals has about 900 quanta over 3".  Absolute encoders (e.g., 
    // bar code sensors) should use the bar code range.
    // Sensors that are inherently analog (e.g., potentiometers, analog
    // distance sensors) can quantize on any arbitrary scale.  In most cases,
    // it's best to use the same 0..65535 scale used for the regular plunger
    // reports.
    uint16_t nativeScale;
    // Scaling factor to convert native readings to abstract units on the
    // 0x0000..0xFFFF scale used in the higher level sensor-independent
    // code.  Multiply a raw sensor position reading by this value to
    // get the equivalent value on the abstract scale.  This is expressed 
    // as a fixed-point real number with a scale of 65536: calculate it as
    //   (65535U*65536U) / (nativeScale - 1);
    uint32_t scalingFactor;
    // Jitter filtering
    int jfWindow;                // window size, in native sensor units
    int jfLo, jfHi;              // bounds of current window
    int jfLast;                  // last filtered reading
    // Reverse the raw reading orientation.  If set, raw readings will be
    // switched to the opposite orientation.  This allows flipping the sensor
    // orientation virtually to correct for installing the physical device
    // backwards.
    bool reverseOrientation;

// --------------------------------------------------------------------------
// Generic image sensor interface for image-based plungers.
// This interface is designed to allow the underlying sensor code to work
// asynchronously to transfer pixels from the sensor into memory using
// multiple buffers arranged in a circular list.  We have a "ready" state,
// which lets the sensor tell us when a buffer is available, and we have
// the notion of "ownership" of the buffer.  When the client is done with
// a frame, it must realease the frame back to the sensor so that the sensor
// can use it for a subsequent frame transfer.
class PlungerSensorImageInterface
    PlungerSensorImageInterface(int npix)
        native_npix = npix;
    // initialize the sensor
    virtual void init() = 0;

    // is the sensor ready?
    virtual bool ready() = 0;
    // Read the image.  This retrieves a pointer to the current frame
    // buffer, which is in memory space managed by the sensor.  This
    // MUST only be called when ready() returns true.  The buffer is
    // locked for the client's use until the client calls releasePix().
    // The client MUST call releasePix() when done with the buffer, so
    // that the sensor can reuse it for another frame.
    virtual void readPix(uint8_t* &pix, uint32_t &t) = 0;
    // Release the current frame buffer back to the sensor.  
    virtual void releasePix() = 0;
    // get the average sensor pixel scan time (the time it takes on average
    // to read one image frame from the sensor)
    virtual uint32_t getAvgScanTime() = 0;
    // Set the minimum integration time (microseconds)
    virtual void setMinIntTime(uint32_t us) = 0;
    // number of pixels on sensor
    int native_npix;

// ----------------------------------------------------------------------------
// Plunger base class for image-based sensors
template<class ProcessResult>
class PlungerSensorImage: public PlungerSensor
    PlungerSensorImage(PlungerSensorImageInterface &sensor, int npix, int nativeScale)
        : PlungerSensor(nativeScale), sensor(sensor)
        axcTime = 0;
        extraIntTime = 0;
        native_npix = npix;
    // initialize the sensor
    virtual void init() { sensor.init(); }

    // is the sensor ready?
    virtual bool ready() { return sensor.ready(); }
    // get the pixel transfer time
    virtual uint32_t getAvgScanTime() { return sensor.getAvgScanTime(); }

    // set extra integration time
    virtual void setExtraIntegrationTime(uint32_t us) { extraIntTime = us; }
    // read the plunger position
    virtual bool readRaw(PlungerReading &r)
        // read pixels from the sensor
        uint8_t *pix;
        uint32_t tpix;
        sensor.readPix(pix, tpix);
        // process the pixels
        int pixpos;
        ProcessResult res;
        bool ok = process(pix, native_npix, pixpos, res);
        // release the buffer back to the sensor
        // adjust the exposure time
        sensor.setMinIntTime(axcTime + extraIntTime);

        // if we successfully processed the frame, read the position
        if (ok)
            r.pos = pixpos;
            r.t = tpix;
        // return the result
        return ok;

    // Send a status report to the joystick interface.
    // See plunger.h for details on the arguments.
    virtual void sendStatusReport(USBJoystick &js, uint8_t flags)
        // get pixels
        uint8_t *pix;
        uint32_t t;
        sensor.readPix(pix, t);

        // start a timer to measure the processing time
        Timer pt;

        // process the pixels and read the position
        int pos, rawPos;
        int n = native_npix;
        ProcessResult res;
        if (process(pix, n, rawPos, res))
            // success - apply the jitter filter
            pos = jitterFilter(rawPos);
            // report 0xFFFF to indicate that the position wasn't read
            pos = 0xFFFF;
            rawPos = 0xFFFF;
        // adjust the exposure time
        sensor.setMinIntTime(axcTime + extraIntTime);

        // note the processing time
        uint32_t processTime = pt.read_us();
        // If a low-res scan is desired, reduce to a subset of pixels.  Ignore
        // this for smaller sensors (below 512 pixels)
        if ((flags & 0x01) && n >= 512)
            // figure how many sensor pixels we combine into each low-res pixel
            const int group = 8;
            int lowResPix = n / group;
            // combine the pixels
            int src, dst;
            for (src = dst = 0 ; dst < lowResPix ; ++dst)
                // average this block of pixels
                int a = 0;
                for (int j = 0 ; j < group ; ++j)
                    a += pix[src++];
                // we have the sum, so get the average
                a /= group;

                // store the down-res'd pixel in the array
                pix[dst] = uint8_t(a);
            // update the pixel count to the reduced array size
            n = lowResPix;
        // figure the report flags
        int jsflags = 0;
        // add flags for the detected orientation: 0x01 for normal orientation,
        // 0x02 for reversed orientation; no flags if orientation is unknown
        int dir = getOrientation();
        if (dir == 1) 
            jsflags |= 0x01; 
        else if (dir == -1)
            jsflags |= 0x02;
        // send the sensor status report headers
        js.sendPlungerStatus(n, pos, jsflags, sensor.getAvgScanTime(), processTime);
        js.sendPlungerStatus2(nativeScale, jfLo, jfHi, rawPos, axcTime);

        // send any extra status headers for subclasses
        extraStatusHeaders(js, res);
        // If we're not in calibration mode, send the pixels
        extern bool plungerCalMode;
        if (!plungerCalMode)
            // send the pixels in report-sized chunks until we get them all
            int idx = 0;
            while (idx < n)
                js.sendPlungerPix(idx, n, pix);
        // release the pixel buffer
    // process an image to read the plunger position
    virtual bool process(const uint8_t *pix, int npix, int &rawPos, ProcessResult &res) = 0;
    // send extra status headers, following the standard headers (types 0 and 1)
    virtual void extraStatusHeaders(USBJoystick &js, ProcessResult &res) { }
    // get the detected orientation
    virtual int getOrientation() const { return 0; }
    // underlying hardware sensor interface
    PlungerSensorImageInterface &sensor;

    // number of pixels
    int native_npix;
    // Auto-exposure time.  This is for use by process() in the subclass.
    // On each frame processing iteration, it can adjust this to optimize
    // the image quality.
    uint32_t axcTime;
    // Extra exposure time.  This is for use by the PC side, mostly for
    // debugging use to allow the PC user to manually adjust the exposure
    // when inspecting captured frames.
    uint32_t extraIntTime;

#endif /* PLUNGER_H */