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.

diff -r 4e8ce0b18915 -r 822a92bc11d2 USBProtocol.h
--- a/USBProtocol.h	Sat Jan 21 19:48:30 2017 +0000
+++ b/USBProtocol.h	Fri Jan 27 23:47:15 2017 +0000
@@ -1,9 +1,39 @@
 // USB Message Protocol
-// This file is purely for documentation, to describe our USB protocol.
-// We use the standard HID setup with one endpoint in each direction.
-// See USBJoystick.cpp/.h for our USB descriptor arrangement.
+// This file is purely for documentation, to describe our USB protocol
+// for incoming messages (host to device).  We use the standard HID setup 
+// with one endpoint in each direction.  See USBJoystick.cpp and .h for
+// the USB descriptors.
+// Our incoming message protocol is an extended version of the protocol 
+// used by the LedWiz.  Our protocol is designed to be 100% backwards
+// compatible with clients using the original LedWiz wire protocol, as long 
+// as they only send well-formed messages in the original protocol.  The
+// "well-formed" part is an important condition, because our extensions to
+// the original protocol all consist of messages that aren't defined in the
+// original protocol and are meaningless to a real LedWiz.
+// The protocol compatibility ensures that all original LedWiz clients can
+// also transparently access a Pinscape unit.  Clients will simply think the
+// Pinscape unit is an LedWiz, thus they'll be able to operate 32 of our
+// ports.  We designate the first 32 ports (ports 1-32) as the ones accessible
+// through the LedWiz protocol.
+// In addition the wire-level protocol compatibility, we can provide legacy
+// LedWiz clients with access to more than 32 ports by emulating multiple
+// virtual LedWiz units.  We can't do this across the wire protocol, since
+// the KL25Z USB interface constrains us to a single VID/PID (which is how
+// LedWiz clients distinguish units).  However, virtuall all legacy LedWiz
+// clients access the device through a shared library, LEDWIZ.DLL, rather
+// than directly through USB.  LEDWIZ.DLL is distributed by the LedWiz's
+// manufacturer and has a published client interface.  We can thus provide
+// a replacement DLL that contains the logic needed to recognize a Pinscape
+// unit and represent it to clients as multiple LedWiz devices.  This allows
+// old clients to access our full complement of ports without any changes
+// to the clients.  We define some extended message types (SBX and PBX)
+// specifically to support this DLL feature.
@@ -151,7 +181,9 @@
 //    bytes 0:1 = 0x8800.  This has the bit pattern 10001 in the high
 //                5 bits, which distinguishes it from regular joystick
 //                reports and from other special report types.
-//    bytes 2:3 = total number of outputs, little endian
+//    bytes 2:3 = total number of configured outputs, little endian.  This
+//                is the number of outputs with assigned functions in the
+//                active configuration.
 //    bytes 4:5 = Pinscape unit number (0-15), little endian
 //    bytes 6:7 = plunger calibration zero point, little endian
 //    bytes 8:9 = plunger calibration maximum point, little endian
@@ -160,6 +192,8 @@
 //                 0x01 -> configuration loaded; 0 in this bit means that
 //                         the firmware has been loaded but no configuration
 //                         has been sent from the host
+//                 0x02 -> SBX/PBX extension features: 1 in this bit means
+//                         that these features are present in this version.
 //    bytes 12:13 = available RAM, in bytes, little endian.  This is the amount
 //                of unused heap (malloc'able) memory.  The firmware generally
 //                allocates all of the dynamic memory it needs during startup,
@@ -288,27 +322,42 @@
-// The real LedWiz protocol has two message types, identified by the first
-// byte of the 8-byte USB packet:
+// The real LedWiz protocol has two message types, "SBA" and "PBA".  The
+// message type can be determined from the first byte of the 8-byte message
+// packet: if the first byte 64 (0x40), it's an SBA message.  If the first
+// byte is 0-49 or 129-132, it's a PBA message.  All other byte values are
+// invalid in the original protocol and have undefined behavior if sent to
+// a real LedWiz.  We take advantage of this to extend the protocol with
+// our new features by assigning new meanings to byte patterns that have no 
+// meaning in the original protocol.
-// 64              -> SBA (64 xx xx xx xx ss uu uu)
-//                    xx = on/off bit mask for 8 outputs
-//                    ss = global flash speed setting (1-7)
-//                    uu = unused
+// "SBA" message:   64 xx xx xx xx ss 00 00
+//     xx = on/off bit mask for 8 outputs
+//     ss = global flash speed setting (valid values 1-7)
+//     00 = unused/reserved; client should set to zero (not enforced, but
+//          strongly recommended in case of future additions)
 // If the first byte has value 64 (0x40), it's an SBA message.  This type of 
 // message sets all 32 outputs individually ON or OFF according to the next 
 // 32 bits (4 bytes) of the message, and sets the flash speed to the value in 
-// the sixth byte.  (The flash speed sets the global cycle rate for flashing
-// outputs - outputs with their values set to the range 128-132 - to a   
-// relative speed, scaled linearly in frequency.  1 is the slowest at about 
-// 2 Hz, 7 is the fastest at about 14 Hz.)
+// the sixth byte.  The flash speed sets the global cycle rate for flashing
+// outputs - outputs with their values set to the range 128-132.  The speed
+// parameter is in ad hoc units that aren't documented in the LedWiz API, but
+// observations of real LedWiz units show that the "speed" is actually the
+// period, each unit representing 0.25s: so speed 1 is a 0.25s period, or 4Hz,
+// speed 2 is a 0.5s period or 2Hz, etc., up to speed 7 as a 1.75s period or
+// 0.57Hz.  The period is the full waveform cycle time.
-// 0-49 or 128-132 -> PBA (bb bb bb bb bb bb bb bb)
-//                    bb = brightness level/flash pattern for one output
+// "PBA" message:  bb bb bb bb bb bb bb bb
+//     bb = brightness level, 0-49 or 128-132
-// If the first byte is any valid brightness setting, it's a PBA message.
-// Valid brightness settings are:
+// Note that there's no prefix byte indicating this message type.  This
+// message is indicated simply by the first byte being in one of the valid
+// ranges.
+// Each byte gives the new brightness level or flash pattern for one part.
+// The valid values are:
 //     0-48 = fixed brightness level, linearly from 0% to 100% intensity
 //     49   = fixed brightness level at 100% intensity (same as 48)
@@ -316,27 +365,17 @@
 //     130  = flashing pattern, on / off (square wave)
 //     131  = flashing pattern, on for 50% duty cycle / fade down
 //     132  = flashing pattern, fade up / on for 50% duty cycle
-// A PBA message sets 8 outputs out of 32.  Which 8 are to be set is 
-// implicit in the message sequence: the first PBA sets outputs 1-8, the 
-// second sets 9-16, and so on, rolling around after each fourth PBA.  
-// An SBA also resets the implicit "bank" for the next PBA to outputs 1-8.
-// Note that there's no special first byte to indicate the PBA message
-// type, as there is in an SBA.  The first byte of a PBA is simply the
-// first output setting.  The way the LedWiz creators conceived this, an
-// SBA message is distinguishable from a PBA because there's no such thing
-// as a brightness level 64, hence 64 is never valid as a byte in an PBA
-// message, hence a message starting with 64 must be something other than
-// an PBA message.
+// This message sets new brightness/flash settings for 8 ports.  There's
+// no port number specified in the message; instead, the port is given by
+// the protocol state.  Specifically, the device has an internal register
+// containing the base port for PBA messages.  On reset AND after any SBA
+// message is received, the base port is set to 0.  After any PBA message
+// is received and processed, the base port is incremented by 8, resetting
+// to 0 when it reaches 32.  The bytes of the message set the brightness
+// levels for the base port, base port + 1, ..., base port + 7 respectively.
-// Our extended protocol uses the same principle, taking advantage of the
-// many other byte values that are also invalid in PBA messages.  To be a 
-// valid PBA message, the first byte must be in the range 0-49 or 129-132.  
-// As already mentioned, byte value 64 indicates an SBA message, so we
-// can't use that one for private extensions.  This still leaves many
-// other byte values for us, though, namely 50-63, 65-128, and 133-255.
@@ -386,9 +425,9 @@
 //             (see above; see also USBJoystick.cpp), then resumes sending normal 
 //             joystick reports.
-//        5 -> Turn all outputs off and restore LedWiz defaults.  Sets output ports
-//             1-32 to OFF and LedWiz brightness/mode setting 48, sets outputs 33 and
-//             higher to brightness level 0, and sets the LedWiz global flash speed to 2.
+//        5 -> Turn all outputs off and restore LedWiz defaults.  Sets all output 
+//             ports to OFF and LedWiz brightness/mode setting 48, and sets the LedWiz
+//             global flash speed to 2.
 //        6 -> Save configuration to flash.  This saves all variable updates sent via
 //             type 66 messages since the last reboot, then automatically reboots the
@@ -433,26 +472,7 @@
 //                 1 = turn relay on
 //                 2 = pulse the relay as though the power-on delay timer fired
-//       12 -> Select virtual LedWiz unit.  This selects a bank of 32 ports that
-//             will be addressed by subsequent SBA and PBA messages.  After this
-//             command is sent, all SBA and PBA messages will address the bank of
-//             ports selected by this command.  Send this command again with a new
-//             bank number to address other ports with SBA/PBA messages.
-//             The rationale for this command is to allow legacy software that only
-//             uses the original LedWiz protocol to access more than 32 ports.  To
-//             do this, we must replace the LEDWIZ.DLL interface library on the PC
-//             with a new version that exposes each Pinscape unit as multiple virtual
-//             LedWiz devices.  The DLL creates a virtual LedWiz unit (each with its
-//             own unit number) for each bank of 32 ports on the Pincape unit.  When
-//             the DLL receives an SBA or PBA command addressed to one of the virtual
-//             LedWiz units, it first sends a "select virtual unit" command (i.e.,
-//             this message) to Pinscape, selecting the appropriate bank of 32 ports
-//             represented by the virtual unit being accessed by the client, then
-//             follows with the SBA/PBA command the client sent.
-//             The third byte of the message is the bank number to select.  Bank 0
-//             is ports 1-32, bank 1 is ports 33-64, and so on.
+//       12 -> Unused
 //       13 -> Get button status report.  The device sends one button status report
 //             in response (see section "2F" above).
@@ -466,6 +486,68 @@
 //        type 65 subtype 6 message (see above).  That saves the settings to flash and
 //        reboots the device, which makes the new settings active.
+// 67  -> "SBX".  This is an extended form of the original LedWiz SBA message.  This
+//        version is specifically designed to support a replacement LEDWIZ.DLL on the
+//        host that exposes one Pinscape device as multiple virtual LedWiz devices,
+//        in order to give legacy clients access to more than 32 ports.  Each virtual
+//        LedWiz represents a block of 32 ports.  The format of this message is the
+//        same as for the original SBA, with the addition of one byte:
+//            67 xx xx xx xx ss pp 00
+//               xx = on/off switches for 8 ports, one bit per port
+//               ss = global flash speed setting for this bank of ports, 1-7
+//               pp = port group: 0 for ports 1-32, 1 for ports 33-64, etc
+//               00 = unused/reserved; client should set to zero
+//        As with SBA, this sets the on/off switch states for a block of 32 ports.
+//        SBA always addresses ports 1-32; SBX can address any set of 32 ports.
+//        We keep a separate speed setting for each group of 32 ports.  The purpose
+//        of the SBX extension is to allow a custom LEDWIZ.DLL to expose multiple
+//        virtual LedWiz units to legacy clients, so clients will expect each unit
+//        to have its separate flash speed setting.  Each block of 32 ports maps to
+//        a virtual unit on the client side, so each block needs its own speed state.
+// 68  -> "PBX".  This is an extended form of the original LedWiz PBA message; it's
+//        the PBA equivalent of our SBX extension above.
+//            68 pp ee ee ee ee ee ee
+//               pp = port group: 0 for ports 1-8, 1 for 9-16, etc
+//               qq = sequence number: 0 for the first 8 ports in the group, etc
+//               ee = brightness/flash values, 6 bits per port, packed into the bytes
+//        The port group 'pp' selects a group of 8 ports.  Note that, unlike PBA,
+//        the port group being updated is explicitly coded in the message, which makes
+//        the message stateless.  This eliminates any possibility of the client and
+//        host getting out of sync as to which ports they're talking about.  This
+//        message doesn't affect the PBA port address state.
+//        The brightness values are *almost* the same as in PBA, but not quite.  We
+//        remap the flashing state values as follows:
+//            0-48 = brightness level, 0% to 100%, on a linear scale
+//            49   = brightness level 100% (redundant with 48)
+//            60   = PBA 129 equivalent, sawtooth
+//            61   = PBA 130 equivalent, square wave (on/off)
+//            62   = PBA 131 equivalent, on/fade down
+//            63   = PBA 132 equivalent, fade up/on
+//        We reassign the brightness levels like this because it allows us to pack
+//        every possible value into 6 bits.  This allows us to fit 8 port settings
+//        into six bytes.  The 6-bit fields are packed into the 8 bytes consecutively
+//        starting with the low-order bit of the first byte.  An efficient way to
+//        pack the 'ee' fields given the brightness values is to shift each group of 
+//        four bytes  into a uint, then shift the uint into three 'ee' bytes:
+//           unsigned int tmp1 = bri[0] | (bri[1]<<6) | (bri[2]<<12) | (bri[3]<<18);
+//           unsigned int tmp2 = bri[4] | (bri[5]<<6) | (bri[6]<<12) | (bri[7]<<18);
+//           unsigned char port_group = FIRST_PORT_TO_ADDRESS / 8;
+//           unsigned char msg[8] = {
+//               68, pp, 
+//               tmp1 & 0xFF, (tmp1 >> 8) & 0xFF, (tmp1 >> 16) & 0xFF,
+//               tmp2 & 0xFF, (tmp2 >> 8) & 0xFF, (tmp2 >> 16) & 0xFF
+//           };
 // 200-228 -> Set extended output brightness.  This sets outputs N to N+6 to the
 //        respective brightness values in the 2nd through 8th bytes of the message
 //        (output N is set to the 2nd byte value, N+1 is set to the 3rd byte value, 
@@ -792,6 +874,48 @@
 //       byte 3 = button number - 1..MAX_BUTTONS, or 0 for none.
+// SPECIAL DIAGNOSTICS VARIABLES:  These work like the array variables below,
+// the only difference being that we don't report these in the number of array
+// variables reported in the "variable 0" query.
+// 220 -> Performance/diagnostics variables.  Items marked "read only" can't
+//        be written; any SET VARIABLE messages on these are ignored.  Items
+//        marked "diagnostic only" refer to counters or statistics that are
+//        collected only when the diagnostics are enabled via the diags.h
+//        macro ENABLE_DIAGNOSTICS.  These will simply return zero otherwise.
+//          byte 3 = diagnostic index (see below)
+//        Diagnostic index values:
+//          1 -> Main loop cycle time [read only, diagnostic only]
+//               Retrieves the average time of one iteration of the main
+//               loop, in microseconds, as a uint32.  This excludes the
+//               time spent processing incoming messages, as well as any
+//               time spent waiting for a dropped USB connection to be
+//               restored.  This includes all subroutine time and polled
+//               task time, such as processing button and plunger input,
+//               sending USB joystick reports, etc.
+//          2 -> Main loop message read time [read only, diagnostic only]
+//               Retrieves the average time spent processing incoming USB
+//               messages per iteration of the main loop, in microseconds, 
+//               as a uint32.  This only counts the processing time when 
+//               messages are actually present, so the average isn't reduced
+//               by iterations of the main loop where no messages are found.
+//               That is, if we run a million iterations of the main loop,
+//               and only five of them have messages at all, the average time
+//               includes only those five cycles with messages to process.
+//          3 -> PWM update polling time [read only, diagnostic only]
+//               Retrieves the average time, as a uint32 in microseconds,
+//               spent in the PWM update polling routine.
+//          4 -> LedWiz update polling time [read only, diagnostic only]
+//               Retrieves the average time, as a uint32 in microseconds,
+//               units, spent in the LedWiz flash cycle update routine.
 // ARRAY VARIABLES:  Each variable below is an array.  For each get/set message,
 // byte 3 gives the array index.  These are grouped at the top end of the variable 
 // ID range to distinguish this special feature.  On QUERY, set the index byte to 0