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

/media/uploads/mjr/pinscape_no_background_small_L7Miwr6.jpg

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 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 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 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 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.

AltAnalogIn/AltAnalogIn.h

Committer:
mjr
Date:
12 months ago
Revision:
109:310ac82cbbee
Parent:
104:6e06e0f4b476

File content as of revision 109:310ac82cbbee:

#ifndef ALTANALOGIN_H
#define ALTANALOGIN_H

// This is a modified version of Scissors's FastAnalogIn, customized 
// for the needs of the Pinscape linear image sensor interfaces.  This
// class has a bunch of features to make it even faster than FastAnalogIn,
// including support for 8-bit and 12-bit resolution modes, continuous
// sampling mode, coordination with DMA to move samples into memory
// asynchronously, and client selection of the ADC timing modes.
//
// We need all of this special ADC handling because the image sensors
// have special timing requirements that we can only meet with the
// fastest modes offered by the KL25Z ADC.  The image sensors all
// operate by sending pixel data as a serial stream of analog samples,
// so the minimum time to read a frame is approximately <number of
// pixels in the frame> times <ADC sampling time per sample>.  The
// sensors we currently support vary from 1280 to 1546 pixels per frame.
// With the fastest KL25Z modes, that works out to about 3ms per frame,
// which is just fast enough for our purposes.  Using only the default
// modes in the mbed libraries, frame times are around 30ms, which is
// much too slow to accurately track a fast-moving plunger.
//
// This class works ONLY with the KL25Z.
//
// Important!  This class can't coexist at run-time with the standard
// mbed library version of AnalogIn, or with the original version of 
// FastAnalogIn.  All of these classes program the ADC configuration 
// registers with their own custom settings.  These registers are a 
// global resource, and the different classes all assume they have 
// exclusive control, so they don't try to coordinate with anyone else 
// programming the registers.  A program that uses AltAnalogIn in one 
// place will have to use AltAnalogIn exclusively throughout the 
// program for all ADC interaction.  (It *is* okay to statically link
// the different classes, as long as only one is actually used at
// run-time.  The Pinscape software does this, and selects the one to
// use at run-time according to which plunger class is selected.)

/*
 * Includes
 */
#include "mbed.h"
#include "pinmap.h"
#include "SimpleDMA.h"

// KL25Z definitions
#if defined TARGET_KLXX

// Maximum ADC clock for KL25Z in <= 12-bit mode - 18 MHz per the data sheet
#define MAX_FADC_12BIT      18000000

// Maximum ADC clock for KL25Z in 16-bit mode - 12 MHz per the data sheet
#define MAX_FADC_16BIT      12000000

#define CHANNELS_A_SHIFT     5          // bit position in ADC channel number of A/B mux
#define ADC_CFG1_ADLSMP      0x10       // long sample time mode
#define ADC_SC1_AIEN         0x40       // interrupt enable
#define ADC_SC2_ADLSTS(mode) (mode)     // long sample time select - bits 1:0 of CFG2
#define ADC_SC2_DMAEN        0x04       // DMA enable
#define ADC_SC2_ADTRG        0x40       // Hardware conversion trigger
#define ADC_SC3_CONTINUOUS   0x08       // continuous conversion mode
#define ADC_SC3_AVGE         0x04       // averaging enabled
#define ADC_SC3_AVGS_4       0x00       // 4-sample averaging
#define ADC_SC3_AVGS_8       0x01       // 8-sample averaging
#define ADC_SC3_AVGS_16      0x02       // 16-sample averaging
#define ADC_SC3_AVGS_32      0x03       // 32-sample averaging
#define ADC_SC3_CAL          0x80       // calibration - set to begin calibration
#define ADC_SC3_CALF         0x40       // calibration failed flag

#define ADC_8BIT             0          // 8-bit resolution
#define ADC_12BIT            1          // 12-bit resolution
#define ADC_10BIT            2          // 10-bit resolution
#define ADC_16BIT            3          // 16-bit resolution

// SIM_SOPT7 - enable alternative conversion triggers
#define ADC0ALTTRGEN         0x80

// SIM_SOPT7 ADC0TRGSEL bits for TPMn, n = 0..2
#define ADC0TRGSEL_TPM(n)    (0x08 | (n))  // select TPMn overflow


#else
    #error "This target is not currently supported"
#endif

#if !defined TARGET_LPC1768 && !defined TARGET_KLXX && !defined TARGET_LPC408X && !defined TARGET_LPC11UXX && !defined TARGET_K20D5M
    #error "Target not supported"
#endif


class AltAnalogIn {

public:
     /** Create an AltAnalogIn, connected to the specified pin
     *
     * @param pin AnalogIn pin to connect to
     * @param continuous true to enable continue sampling mode
     * @param long_sample_clocks long sample mode: 0 to disable, ADC clock count to enable (6, 10, 16, or 24)
     * @param averaging number of averaging cycles (1, 4, 8, 16, 32)
     * @param sample_bits sample size in bits (8, 10, 12, 16)
     */
    AltAnalogIn(PinName pin, bool continuous = false, int long_sample_clocks = 0, int averaging = 1, int sample_bits = 8);
    
    ~AltAnalogIn( void )
    {
    }
    
    // Calibrate the ADC.  Per the KL25Z reference manual, this should be
    // done after each CPU reset to get the best accuracy from the ADC.
    //
    // The calibration process runs synchronously (blocking) and takes
    // about 2ms.  Per the reference manual guidelines, we calibrate
    // using the same timing parameters configured in the constructor,
    // but we use the maximum averaging rounds.
    //
    // The calibration depends on the timing parameters, so if multiple
    // AltAnalogIn objects will be used in the same application, the
    // configuration established for one object might not be ideal for 
    // another.  The advice in the reference manual is to calibrate once
    // at the settings where the highest accuracy will be needed.  It's
    // also possible to capture the configuration data from the ADC
    // registers after a configuration and restore them later by writing
    // the same values back to the registers, for relatively fast switching
    // between calibration sets, but that's beyond the scope of this class.
    void calibrate();
    
    // Initialize DMA.  This connects the ADC port to the given DMA
    // channel.  This doesn't actually initiate a transfer; this just
    // connects the ADC to the DMA channel for later transfers.  Use
    // the DMA object to set up a transfer, and use one of the trigger
    // modes (e.g., start() for software triggering) to initiate a
    // sample.
    void initDMA(SimpleDMA *dma);
    
    // Enable interrupts.  This doesn't actually set up a handler; the
    // caller is responsible for that.  This merely sets the ADC registers
    // so that the ADC generates an ADC0_IRQ interrupt request each time
    // the sample completes.
    //
    // Note that the interrupt handler must read from ADC0->R[0] before
    // returning, which has the side effect of clearning the COCO (conversion
    // complete) flag in the ADC registers.  When interrupts are enabled,
    // the ADC asserts the ADC0_IRQ interrupt continuously as long as the
    // COCO flag is set, so if the ISR doesn't explicitly clear COCO before
    // it returns, another ADC0_IRQ interrupt will immediate occur as soon
    // as the ISR returns, so we'll be stuck in an infinite loop of calling
    // the ISR over and over.
    void enableInterrupts();
        
    // Start a sample.  This sets the ADC multiplexer to read from
    // this input and activates the sampler.
    inline void start()
    {
        // select my channel
        selectChannel();
        
        // set our SC1 bits - this initiates the sample
        ADC0->SC1[1] = sc1;
        ADC0->SC1[0] = sc1;
    }

    // Set the ADC to trigger on a TPM channel, and start sampling on
    // the trigger.  This can be used to start ADC samples in sync with a 
    // clock signal we're generating via a TPM.  The ADC is triggered each 
    // time the TPM counter overflows, which makes it trigger at the start 
    // of each PWM period on the unit.
    void setTriggerTPM(int tpmUnitNumber);
    
    // stop sampling
    void stop()
    {
        // set the channel bits to binary 11111 to disable sampling
        ADC0->SC1[0] = 0x1F;
    }
    
    // Resume sampling after a pause.
    inline void resume()  
    {
        // restore our SC1 bits
        ADC0->SC1[1] = sc1;
        ADC0->SC1[0] = sc1;
    }    
    
    // Wait for the current sample to complete.
    //
    // IMPORTANT!  DO NOT use this if DMA is enabled on the ADC.  It'll
    // always gets stuck in an infinite loop, because the CPU will never
    // be able to observe the COCO bit being set when DMA is enabled.  The
    // reason is that the DMA controller always reads its configured source
    // address when triggered.  The DMA source address for the ADC is the 
    // ADC result register ADC0->R[0], and reading that register by any 
    // means clears COCO.  And the DMA controller ALWAYS gets to it first,
    // so the CPU will never see COCO set when DMA is enabled.  It doesn't
    // matter whether or not a DMA transfer is actually running, either -
    // it's enough to merely enable DMA on the ADC.
    inline void wait()
    {
        while (!isReady()) ;
    }
    
    // Is the sample ready?
    //
    // NOTE: As with wait(), the CPU will NEVER observe the COCO bit being
    // set if DMA is enabled on the ADC.  This will always return false if
    // DMA is enabled.  (Not our choice - it's a hardware feature.)
    inline bool isReady()
    {
        return (ADC0->SC1[0] & ADC_SC1_COCO_MASK) != 0;
    }

    
private:
    uint32_t id;                // unique ID
    SimpleDMA *dma;             // DMA controller, if used
    char ADCnumber;             // ADC number of our input pin
    char ADCmux;                // multiplexer for our input pin (0=A, 1=B)
    uint32_t sc1;               // SC1 register settings for this input
    uint32_t sc1_aien;
    uint32_t sc2;               // SC2 register settings for this input
    uint32_t sc3;               // SC3 register settings for this input
    
    // Switch to this channel if it's not the currently selected channel.
    // We do this as part of start() (software triggering) or any hardware
    // trigger setup.
    static int lastMux;
    static uint32_t lastId;
    void selectChannel()
    {
        // update the MUX bit in the CFG2 register only if necessary
        if (lastMux != ADCmux) 
        {
            // remember the new register value
            lastMux = ADCmux;
        
            // select the multiplexer for our ADC channel
            if (ADCmux)
                ADC0->CFG2 |= ADC_CFG2_MUXSEL_MASK;
            else
                ADC0->CFG2 &= ~ADC_CFG2_MUXSEL_MASK;
        }
        
        // update the SC2 and SC3 bits only if we're changing inputs
        if (id != lastId) 
        {
            // set our ADC0 SC2 and SC3 configuration bits
            ADC0->SC2 = sc2;
            ADC0->SC3 = sc3;
        
            // we're the active one now
            lastId = id;
        }
    }
    
    // Unselect the channel.  This clears our internal flag for which
    // configuration was selected last, so that we restore settings on
    // the next start or trigger operation.
    void unselectChannel() { lastId = 0; }
};

// 8-bit sampler subclass
class AltAnalogIn_8bit : public AltAnalogIn
{
public:
    AltAnalogIn_8bit(PinName pin, bool continuous = false, int long_sample_clocks = 0, int averaging = 1) :
        AltAnalogIn(pin, continuous, long_sample_clocks, averaging, 8) { }

    /** Returns the raw value
    *
    * @param return Unsigned integer with converted value
    */
    inline uint16_t read_u16()
    {
        // wait for the hardware to signal that the sample is completed
        wait();
    
        // return the result register value
        return (uint16_t)ADC0->R[0] << 8;  // convert 16-bit to 16-bit, padding with zeroes
    }
    
    /** Returns the scaled value
    *
    * @param return Float with scaled converted value to 0.0-1.0
    */
    float read(void)
    {
        unsigned short value = read_u16();
        return value / 65535.0f;
    }
    
    /** An operator shorthand for read()
    */
    operator float() { return read(); }
};

// 16-bit sampler subclass
class AltAnalogIn_16bit : public AltAnalogIn
{
public:
    AltAnalogIn_16bit(PinName pin, bool continuous = false, int long_sample_clocks = 0, int averaging = 1) :
        AltAnalogIn(pin, continuous, long_sample_clocks, averaging, 16) { }

    /** Returns the raw value
    *
    * @param return Unsigned integer with converted value
    */
    inline uint16_t read_u16()
    {
        // wait for the hardware to signal that the sample is completed
        wait();
    
        // return the result register value
        return (uint16_t)ADC0->R[0];
    }
    
    /** Returns the scaled value
    *
    * @param return Float with scaled converted value to 0.0-1.0
    */
    float read(void)
    {
        unsigned short value = read_u16();
        return value / 65535.0f;
    }
    
    /** An operator shorthand for read()
    */
    operator float() { return read(); }
};

#endif