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.


12 months ago

File content as of revision 109:310ac82cbbee:

// IR Remote Transmitter
// This class lets you control an IR emitter LED connected to a GPIO port 
// to transmit remote control codes using numerous standard and proprietary 
// protocols.  You can use this to send remote codes to any device with
// a typical IR remote, such as A/V equipment, home automation devices, etc.
// You can also use this with the companion IR Receiver class running on
// a separate KL25Z to send IR commands to the other device.
// We do all of our transmissions with specific protocols rather than raw
// IR signals.  Every remote control has its own way of representing a
// string of data bits as a series of timed IR flashes.  The exact mapping
// between data bits and IR flashes is the protocol.  There are some quasi
// industry standard protocols, where several companies use the same format
// for their codes, but there are many proprietary protocols as well.  We
// have handlers for the most widely used protocols:  NEC, Sony, Philips RC5
// and RC6, Pioneer, Panasonic, and several others.  If your device isn't
// covered yet, it could probably be added, since we've tried to design
// the system to make it easy to add new protocols.
// When you transmit a code, you specify it in terms of the protocol to use 
// and the "code" value to send.  A "code" is just the data value for a
// particular key on a particular remote control, usually expressed as a 
// hex number.  There are published tables of codes for many remotes, but
// unfortunately they're not very consistent in how they represent the hex
// code values, so you'll often see the same key represented with different
// hex codes in different published tables.  We of course have our own way
// of mapping the hex codes; we've tried to use the format that the original
// manufacturer uses in their tales, if they publish them at all, but these
// may or may not be consistent with what you find in any tables you consult.
// So your best bet for finding the right codes to use here is usually to 
// "learn" the codes using our companion class IRReceiver.  That class has a 
// protocol decoder for each protocol transmitter we can use here, so if you
// set that up and point a remote at it, it will tell you the exact code we
// use for the key.
// The transmitter class provides a "virtual remote control" interface.
// This gives you an imaginary remote control keypad, with a set of
// virtual buttons programmed for individual remote control commands.
// You specify the protocol and command code for each virtual button.
// You can use different protocols for different buttons.
// How to use the software
// First, create an instance of IRTransmitter, telling it which pin the
// IR emitter is connected to (see below for wiring instructions) and how
// many virtual remote control keys you want.  The pin must be PWM capable.
//    IRTransmitter *tx = new IRTransmitter(PTC9, 32);
// Next, program the virtual remote keys.  For each key, set the IR protocol
// to use (an IRPRO_xxx code from IRProtocolID.h), the "ditto" mode (more on
// this below), and the hex code for the command.
//    // program virtual button #0 with Sony 20-bit code 0x123, no dittos
//    tx->programButton(0, IRPRO_SONY20, false, 0x123);
// Now you're set up to transmit.  In your main loop, decide when it's time
// to transmit a button, such as by monitoring a physical pushbutton via a
// GPIO DigitalIn pin.  When you want to transmit a code, just tell the
// transmitter that your virtual button is pressed, by calling pushButton()
// with the virtual button ID (corresponding to a virtual button ID you
// previously programmed wtih programButton()) and a status of 'true',
// meaning that the button is pressed.
//    tx->pushButton(0, true);  // push virtual button #0
// This starts the transmission and returns immediately.  The transmission
// proceeds in the background (via timer interrupts), so your main loop can
// go about its other business without waiting for the transmission to
// finish.  Most remote codes take 50ms to 100ms to transmit, and you don't
// usually want to stall an MCU app for that long.
// If a prior transmission is still in progress when you call pushButton(), 
// the new transmission doesn't interrupt the previous one.  Every code is
// sent as a complete unit to ensure data integrity, so the old one has to
// finish before the new one starts.  Some protocols have minimum repeat
// counts, and the transmitter takes this into account as well.  For example,
// the Sony protocols require each command to be sent at least three times,
// even if the button is only tapped for a brief instant.  So if you send
// a Sony code, a new command won't start transmitting until the last command
// has been sent completely, not just once, but at least three times.
// Once the transmitter starts sending the code for a new button, it keeps
// sending the same code on auto-repeat until you either un-press the
// virtual button or press a new virtual button.  Handling auto-repeat
// in the transmitter like this has an important benefit, besides just making
// the API simpler: it allows the transmitter to use the proper coding for
// the repeats according to the rules of the protocol.  Some protocols use
// a different format for the first code of a key press and auto-repeats
// of the same key.  Some protocols also have other repetition features,
// such as "toggle bits" or sequence counters.  The protocol handlers use
// the appropriate handling for their protocols, so you only have to think
// in terms of when the virtual buttons are pressed and un-pressed, without
// worrying about whether a toggle bit or a "ditto" code or a sequence
// counter is needed.
// When the button is no longer pressed, call pushButton() again with a
// status of 'false':
//    tx->pushButton(0, false);
// Multiple button presses use simple PC keyboard-like semantics.  At any
// given time, there can be only one pressed button.  When you call 
// pushButton(N, true), N becomes the pressed button, which means that the
// previous pressed button (if any) is forgotten.  As mentioned above, this
// doesn't cancel the previous transmission if it's still in progress.  The
// transmitter continues with the last code until it's finished.  When it
// finishes with a code, the transmitter looks to see if the same button is
// still pressed.  If so, it starts a new transmission for the same button,
// using the appropriate repeat code.  If a new button is pressed, the
// transmitter starts transmitting the new button's code.  If no button is
// pressed, the transmitter stops sending and becomes idle until you press
// another button.
// Note that button presses aren't queued.  Suppose you press button #0
// (while no other code is being sent): this starts transmitting the code
// for button #0 and returns.  Now suppose that a very short time later, 
// while that first send is still in progress, you briefly press and release
// button #1.  Button #1 will never be sent in this case.  When you press
// button #1, the transmitter is still sending the first code, so all it
// does at this point is mark button #1 as the currently pressed button,
// replacing button #0.  But as explained above, this doesn't cancel the
// button #0 code transmission in progress.  That continues until the
// complete code has been sent.  At that point, the transmitter looks to
// see which button is pressed, and discovers that NO button is pressed:
// you already told it button #1 was released.  So the transmitter simply
// stops sending and becomes idle.
// How to determine command codes and the "ditto" mode
// Our command codes are expressed as 64-bit integers.  The code numbers
// are in essence the data bits transmitted in the IR signal, but the mapping
// between the IR data bits and the 64-bit code value is different for each
// protocol.  We've tried to make our codes match the numbers shown in the
// tables published by the respective manufacturers for any given remote,
// but you might also find third-party tables that have completely different
// mappings.  The easiest thing to do, really, is to ignore all of that and
// just treat the codes as arbitrary, opaque identifiers, and identify the
// codes for the remote you want to use by "learning" them.  That is, set up
// a receiver with our companion class IRReceiver, point your remote at it,
// and see what IRReceiver reports as the decoded value for each button. 
// Simply use the same code value for each button when sending.
// The "ditto" flag is ignored for most protocols, but it's important for a
// few, such as the various NEC protocols.  This tells the sender whether to
// use the protocol's special repeat code for auto-repeats (true), or to send
// send the same key code repeatedly (false).  The concept of dittos only
// applies to a few protocols; most protocols just do the obvious thing and
// send the same code repeatedly when you hold down a key.  But the NEC
// protocols and a few others have special coding for repeated keys.  It's 
// important to use the special coding for devices that expect it, because 
// it lets them distinguish auto-repeat from multiple key presses, which
// can affect how they respond to certain commands.  The tricky part is that 
// manufacturers aren't always consistent about using dittos even when it's
// a standard part of the protocol they're using, so you have to determine
// whether or not to use it on a per-device basis.  The easiest way to do
// this is just like learning codes: set up a receiever with IRReceiver and
// see what it reports.  But this time, you're interested in what happens
// when you hold down a key.  You'll always get one ordinary report first,
// but check what happens for the repeats.  If IRReceiver reports the same 
// code repeatedly, set dittos = false when sending those codes.  If the
// repeats have the "ditto bit" set, though, set dittos = true when sending.
// How to wire an IR emitter
// Any IR LED should work as the emitter.  I used a Vishay TSAL6400 for my
// reference/testing implementation.  The TSAL6400 is quite bright, so it
// should send signals well across fairly large distances.
// WARNING!  DON'T connect the LED directly to the GPIO pin.  KL25Z GPIO
// pins have very low current limits - a typical IR emitter LED draws
// enough current to damage or destroy the KL25Z.  You'll need to build a
// simple transistor circuit to interface with the LED.  You'll need a
// common small signal NPN transistor (such as a 2222 or 2N4401), a 2.2K
// resistor, the IR LED, of course, and a current-limiting resistor for
// the LED.  Choose the current-limiting resistor by plugging your LED's
// specs into an LED resistor calculator, using a 5V supply voltage.  Now
// connect the GPIO pin to the current-limiting resistor, connect the
// resistor to the LED anode (+), connect the LED cathode (-) to the NPN
// collector, connect the NPN emitter to ground, connect the NPN base to
// the 2.2K resistor, and connect the 2.2K resistor to the GPIO pin.
// It's simple enough for a schematic rendered in ASCII art:
//       +5V   (from the KL25Z +5V pin, or directly from
//        |     the KL25Z's power supply)
//        <
//        >  R1 - use an LED resistor calculator to choose
//        <       the resistor size based on your selected 
//        |       LED's forward current & voltage and 5V source
//       ---  +
//       \ /  LED - Infrared emitter (e.g., Vishay TSAL6400)
//       ---  -
//        |
//        |
//         \|     2.2K
//          |-----/\/\/\---> to this GPIO pin
//         /|
//        v
//        |
//      -----
//       ---   Ground (KL25Z GND pin, or ground on the
//        -            KL25Z's power supply)
// If you want to be able to see the transmitter in action, you can connect
// another LED (a blue one, say) and its own current-limiting resistor in
// parallel with the R1 + IR LED circuit.  Let's call the blue LED's
// resistor R2.  Connect R2 to +5V, connect the other end of R2 to the
// blue LED (+), and connect the blue LED (-) to the NPN collector.  This
// will make the blue LED flash in sync with the IR LED.  IR remote control
// codes are slow enough that you'll be able to see the blue LED come on
// and flicker during each transmission, although the "bits" are too fast
// to see individually with the naked eye.  The detector shouldn't be 
// bothered by the extra light since these sensors have optical filters 
// that block most of the incoming light outside of the IR band the sensor 
// is looking for.


#include <mbed.h>

#include "NewPwm.h"
#include "IRRemote.h"
#include "IRCommand.h"
#include "IRProtocols.h"

// IR Remote Transmitter
class IRTransmitter
    // Construct.  
    // 'pin' is the GPIO pin controlling the IR LED.  The pin must be 
    // PWM-capable.  (Note also that each PWM channel on the KL25Z is 
    // shared among multiple pins, so be sure you're using a pin connected 
    // to a channel that isn't already used elsewhere in your application.)
    // Don't connect the LED directly to this pin; see the circuit diagram
    // at the top of the file for details of how to connect it through a
    // transistor to safely boost the current to LED levels.
    // 'nButtons' is the number of virtual button slots to allocate.  Each
    // slot represents a virtual remote control button that can be programmed
    // with a remote code to transmit.  Allocate as many slots as you need
    // for unique commands or buttons.  Note that the caller is responsible
    // for deciding when a button is pressed; if you want to tie these to
    // physical buttons, you'll need to create your own DigitalIn objects
    // for the pins, monitor them, and call pushButton() to press and
    // release virtual buttons when the physical button states change.
    IRTransmitter(PinName pin, int nButtons) : ledPin(pin)
        // make sure the protocol singletons are allocated
        // no command is active
        curBtnId = -1;
        // allocate the command list
        buttons = new ButtonCmd[nButtons];
        // the transmitter "thread" isn't yet running
        txRunning = false;
        txBtnId = -1;
        txProtocol = 0;
        delete[] buttons;
    // Program the command code for a virtual button
    void programButton(int buttonId, int protocolId, bool dittos, uint64_t cmdCode)
        ButtonCmd &btn = buttons[buttonId]; = protocolId;
        btn.dittos = dittos;
        btn.cmd = cmdCode;
    // Push a virtual button.
    // When this is called, we'll start transmitting the command code
    // associated with the button immediately if no other transmission
    // is already in progress.  On the other hand, if a transmission of
    // a prior command code is already in progress, the previous command
    // isn't interrupted; we always send whole commands, and never
    // interrupt a command in progress.  Instead, the new button is
    // set as pending.  As soon as the prior transmission finishes,
    // the pending button becomes the current button and we start
    // transmitting its code - but only if the button is still pressed
    // when the previous code finishes.  This means that if you both 
    // press and release a button during the time that another 
    // transmission is in progress, the new button will never be 
    // transmitted.  We operate this way to keep things simple and
    // consistent when it comes to more than just one pending button.
    // This way we don't have to consider queues of pending buttons
    // or create mechanisms for canceling pending commands.
    // If the button is still down when its first transmission ends,
    // and no other button has been pressed in the meantime, the button
    // will auto-repeat.  This continues as long as the button is still
    // pressed and no other button has been pressed.
    // Only one code can be transmitted at a time, obviously.  The
    // semantics for multiple simultaneous button presses are like those
    // of a PC keyboard.  Suppose you press button A, then a while later,
    // while A is still down, you press B.  Then a while later still,
    // you press C, continuing to hold both A and B down.  We transmit
    // A repeatedly until you press B, at which point we finish sending
    // the current repeat of A (we never interrupt a code in the middle:
    // once started, a code is always finished whole) and start sending
    // B.  B continues to repeat until you press C, at which point we
    // finish the last repetition of B and start sending C.  Once A or
    // B have been superseded, it makes no difference whether you continue
    // to hold them down or release them.  They'll never start repeating
    // again, even if you then release C while A and B are still down.
    void pushButton(int id, bool on)
        if (on)
            // make this the current command
            curBtnId = id;

            // start the transmitter
            // if this is the current command, cancel it
            if (id == curBtnId)
                curBtnId = -1;
    // Is a transmission in progress?
    bool isSending() const { return txRunning; }

    // Start the transmitter "thread", if it's not already running.  The
    // thread is actually just a series of timer interrupts; each interrupt
    // sets the next interrupt at an appropriate interval, so the effect is
    // like a thread.
    void txStart()
        if (!txRunning)
            // The thread isn't running.  Note that this means that there's
            // no possibility that txRunning will change out from under us
            // asynchronously, since there's no pending interrupt handler
            // to change it.  Mark the thread as running.
            txRunning = true;
            // Directly invoke the thread handler for the first call.  It
            // will normally run in interrupt context, but since there's
            // no pending interrupt yet that would re-enter it, we can
            // launch it first in application context.  If there's work
            // pending, it'll kick off the transmission and schedule the
            // next timer interrupt to continue the thread.
    // Transmitter "thread" main.  This handles the timer interrupt for each
    // event in a transmission.
    void txThread()
        // if we're working on a command, process the next step
        if (txProtocol != 0)
            // Determine if the virtual button for the current transmission
            // is still pressed.  It's still pressed if we have a valid 
            // transmitting button ID, and the current pressed button is the 
            // same as the transmitting button.
            txState.pressed = (txBtnId != -1 && txBtnId == curBtnId);

            // Perform the next step via the protocol handler.  The handler
            // returns a positive time value for the next timeout if it still
            // has more work to do.
            int t = txProtocol->txStep(&txState);
            // check if the transmission is done
            if (t > 0)
                // The handler returned a positive time value, so it has
                // more work to do.  That means we're done here - just set
                // the next timeout and exit the interrupt handler.
                txTimeout.attach_us(this, &IRTransmitter::txThread, t);
                // The transmission is done.  Clear the send data.
                txBtnId = -1;
                txProtocol = 0;
        // If we made it here, the transmitter is now idle.  Check to
        // see if we have a new virtual button press.
        if (curBtnId != -1)
            // load the command
            txBtnId = curBtnId;
            txCmd = buttons[curBtnId];
            txProtocol = IRProtocol::senderForId(;
            // If we found a protocol handler, start the transmission
            if (txProtocol != 0)
                // fill in the transmission state object with the new command
                // details
                txState.cmdCode = txCmd.cmd;
                txState.protocolId =;
                txState.dittos = txCmd.dittos;
       = &ledPin;
                txState.pressed = true;
                // reset the transmission step counters
                txState.step = 0;
                txState.bit = 0;
                txState.bitstep = 0;
                txState.rep = 0;
                // this is a new transmission, so toggle the toggle bit
                txState.toggle ^= 1;
                // Turn off the IR and set the PWM frequency of the IR LED to
                // the carrier frequency for the chosen protocol

                // start the transmission timer
                // initiate the transmission
                int t = txProtocol->txStart(&txState);
                // set the timer for the next step of the transmission, then
                // we're done
                txTimeout.attach_us(this, &IRTransmitter::txThread, t);
        // If we made it here, there's no transmission in progress,
        // so the thread is no longer running.
        txRunning = false;

    // LED output pin controlling the IR LED.  The pin must be PWM-capable.
    // WARNING!  Don't connect the IR LED directly to the pin.  See wiring
    // diagram at the top of the file.
    NewPwmOut ledPin;
    // Virtual button slots.  Each slot represents a virtual remote control
    // button, containing a preprogrammed IR command code to send when the 
    // button is pressed.  Program a button by calling programButton().
    // Press a button by calling pushButton().
    struct ButtonCmd
        uint64_t cmd;           // command code
        uint8_t pro;            // protocol ID (IRPRO_xxx)
        uint8_t dittos : 1;     // use "ditto" codes for auto-repeat
    } __attribute__ ((packed));
    ButtonCmd *buttons;
    // Current active virtual button ID.   This is managed in application
    // context and read in interrupt context.  This represents the currently 
    // pushed button.
    int curBtnId;
    // Is the transmitter "thread" running?  This is true when a timer is
    // pending, false if not.  The timer interrupt handler clears this
    // before exiting on its last run of a transmission.
    // Synchronization: if txRunning is false, no timer interrupt is either
    // running or pending, so there's no possibility that anyone else will
    // change it, so it's safe for the application to test and set it.  If
    // txRunning is true, only interrupt context can change it, so application
    // context can only read it.
    volatile bool txRunning;
    // Transmitter thread timeout
    Timeout txTimeout;
    // Command ID being transmitted in the background "thread".  The thread
    // loads this from curBtnID whenever it's out of other work to do.
    int txBtnId;
    // Protocol for the current transmission
    IRProtocol *txProtocol;
    // Command value we're currently transmitting
    ButtonCmd txCmd;
    // Protocol state.  This is for use by the individual protocol
    // classes to keep track of their state while the transmission
    // proceeds.
    IRTXState txState;