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 potentiometer (which determines the position via the changing electrical resistance in the pot); a quadrature sensor (which counts bars printed on a special guide rail that it moves along); and an IR distance sensor (which determines the position by sending pulses of light at the plunger and measuring the round-trip travel time). The Build Guide explains how to set up each type of sensor.

Nudging: The KL25Z (the little microcontroller that the software runs on) has a built-in accelerometer. The Pinscape software uses it to sense when you nudge the cabinet, and feeds the acceleration data to the pinball software on the PC. This turns physical nudges into virtual English on the ball. The accelerometer is quite sensitive and accurate, so we can measure the difference between little bumps and hard shoves, and everything in between. The result is natural and immersive.

Buttons: You can wire real pinball buttons to the KL25Z, and the software will translate the buttons into PC input. You have the option to map each button to a keyboard key or joystick button. You can wire up your flipper buttons, Magna Save buttons, Start button, coin slots, operator buttons, and whatever else you need.

Feedback devices: You can also attach "feedback devices" to the KL25Z. Feedback devices are things that create tactile, sound, and lighting effects in sync with the game action. The most popular PC pinball emulators know how to address a wide variety of these devices, and know how to match them to on-screen action in each virtual table. You just need an I/O controller that translates commands from the PC into electrical signals that turn the devices on and off. The Pinscape Controller can do that for you.

Expansion Boards

There are two main ways to run the Pinscape Controller: standalone, or using the "expansion boards".

In the basic standalone setup, you just need the KL25Z, plus whatever buttons, sensors, and feedback devices you want to attach to it. This mode lets you take advantage of everything the software can do, but for some features, you'll have to build some ad hoc external circuitry to interface external devices with the KL25Z. The Build Guide has detailed plans for exactly what you need to build.

The other option is the Pinscape Expansion Boards. The expansion boards are a companion project, which is also totally free and open-source, that provides Printed Circuit Board (PCB) layouts that are designed specifically to work with the Pinscape software. The PCB designs are in the widely used EAGLE format, which many PCB manufacturers can turn directly into physical boards for you. The expansion boards organize all of the external connections more neatly than on the standalone KL25Z, and they add all of the interface circuitry needed for all of the advanced software functions. The big thing they bring to the table is lots of high-power outputs. The boards provide a modular system that lets you add boards to add more outputs. If you opt for the basic core setup, you'll have enough outputs for all of the toys in a really well-equipped cabinet. If your ambitions go beyond merely well-equipped and run to the ridiculously extravagant, just add an extra board or two. The modular design also means that you can add to the system over time.

Expansion Board project page

Update notes

If you have a Pinscape V1 setup already installed, you should be able to switch to the new version pretty seamlessly. There are just a couple of things to be aware of.

First, the "configuration" procedure is completely different in the new version. Way better and way easier, but it's not what you're used to from V1. In V1, you had to edit the project source code and compile your own custom version of the program. No more! With V2, you simply install the standard, pre-compiled .bin file, and select options using the Pinscape Config Tool on Windows.

Second, if you're using the TSL1410R optical sensor for your plunger, there's a chance you'll need to boost your light source's brightness a little bit. The "shutter speed" is faster in this version, which means that it doesn't spend as much time collecting light per frame as before. The software actually does "auto exposure" adaptation on every frame, so the increased shutter speed really shouldn't bother it, but it does require a certain minimum level of contrast, which requires a certain minimal level of lighting. Check the plunger viewer in the setup tool if you have any problems; if the image looks totally dark, try increasing the light level to see if that helps.

New Features

V2 has numerous new features. Here are some of the highlights...

Dynamic configuration: as explained above, configuration is now handled through the Config Tool on Windows. It's no longer necessary to edit the source code or compile your own modified binary.

Improved plunger sensing: the software now reads the TSL1410R optical sensor about 15x faster than it did before. This allows reading the sensor at full resolution (400dpi), about 400 times per second. The faster frame rate makes a big difference in how accurately we can read the plunger position during the fast motion of a release, which allows for more precise position sensing and faster response. The differences aren't dramatic, since the sensing was already pretty good even with the slower V1 scan rate, but you might notice a little better precision in tricky skill shots.

Keyboard keys: button inputs can now be mapped to keyboard keys. The joystick button option is still available as well, of course. Keyboard keys have the advantage of being closer to universal for PC pinball software: some pinball software can be set up to take joystick input, but nearly all PC pinball emulators can take keyboard input, and nearly all of them use the same key mappings.

Local shift button: one physical button can be designed as the local shift button. This works like a Shift button on a keyboard, but with cabinet buttons. It allows each physical button on the cabinet to have two PC keys assigned, one normal and one shifted. Hold down the local shift button, then press another key, and the other key's shifted key mapping is sent to the PC. The shift button can have a regular key mapping of its own as well, so it can do double duty. The shift feature lets you access more functions without cluttering your cabinet with extra buttons. It's especially nice for less frequently used functions like adjusting the volume or activating night mode.

Night mode: the output controller has a new "night mode" option, which lets you turn off all of your noisy devices with a single button, switch, or PC command. You can designate individual ports as noisy or not. Night mode only disables the noisemakers, so you still get the benefit of your flashers, button lights, and other quiet devices. This lets you play late into the night without disturbing your housemates or neighbors.

Gamma correction: you can designate individual output ports for gamma correction. This adjusts the intensity level of an output to make it match the way the human eye perceives brightness, so that fades and color mixes look more natural in lighting devices. You can apply this to individual ports, so that it only affects ports that actually have lights of some kind attached.

IR Remote Control: the controller software can transmit and/or receive IR remote control commands if you attach appropriate parts (an IR LED to send, an IR sensor chip to receive). This can be used to turn on your TV(s) when the system powers on, if they don't turn on automatically, and for any other functions you can think of requiring IR send/receive capabilities. You can assign IR commands to cabinet buttons, so that pressing a button on your cabinet sends a remote control command from the attached IR LED, and you can have the controller generate virtual key presses on your PC in response to received IR commands. If you have the IR sensor attached, the system can use it to learn commands from your existing remotes.

Yet more USB fixes: I've been gradually finding and fixing USB bugs in the mbed library for months now. This version has all of the fixes of the last couple of releases, of course, plus some new ones. It also has a new "last resort" feature, since there always seems to be "just one more" USB bug. The last resort is that you can tell the device to automatically reboot itself if it loses the USB connection and can't restore it within a given time limit.

More Downloads

  • Custom VP builds: I created modified versions of Visual Pinball 9.9 and Physmod5 that you might want to use in combination with this controller. The modified versions have special handling for plunger calibration specific to the Pinscape Controller, as well as some enhancements to the nudge physics. If you're not using the plunger, you might still want it for the nudge improvements. The modified version also works with any other input controller, so you can get the enhanced nudging effects even if you're using a different plunger/nudge kit. The big change in the modified versions is a "filter" for accelerometer input that's designed to make the response to cabinet nudges more realistic. It also makes the response more subdued than in the standard VP, so it's not to everyone's taste. The downloads include both the updated executables and the source code changes, in case you want to merge the changes into your own custom version(s).

    Note! These features are now standard in the official VP releases, so you don't need my custom builds if you're using 9.9.1 or later and/or VP 10. I don't think there's any reason to use my versions instead of the latest official ones, and in fact I'd encourage you to use the official releases since they're more up to date, but I'm leaving my builds available just in case. In the official versions, look for the checkbox "Enable Nudge Filter" in the Keys preferences dialog. My custom versions don't include that checkbox; they just enable the filter unconditionally.
  • Output circuit shopping list: This is a saved shopping cart at 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 KL25Z can only run one firmware program at a time, so if you install the Pinscape firmware on your KL25Z, it will replace and erase your existing VirtuaPin proprietary firmware. If you do this, the only way to restore your VirtuaPin firmware is to physically ship the KL25Z back to VirtuaPin and ask them to re-flash it. They don't allow you to do this at home, and they don't even allow you to back up your firmware, since they want to protect their proprietary software from copying. For all of these reasons, if you want to run the Pinscape software, I strongly recommend that you buy a "blank" retail KL25Z to use with Pinscape. They only cost about $15 and are available at several online retailers, including Amazon, Mouser, and eBay. The blank retail boards don't come with any proprietary firmware pre-installed, so installing Pinscape won't delete anything that you paid extra for.

With those warnings in mind, if you're absolutely sure that you don't mind permanently erasing your VirtuaPin firmware, it is at least possible to use Pinscape as a replacement for the VirtuaPin firmware. Pinscape uses the same button wiring conventions as the VirtuaPin setup, so you can keep your buttons (although you'll have to update the GPIO pin mappings in the Config Tool to match your physical wiring). As of the June, 2021 firmware, the Vishay VCNL4010 plunger sensor that comes with the VirtuaPin v3 plunger kit is supported, so you can also keep your plunger, if you have that chip. (You should check to be sure that's the sensor chip you have before committing to this route, if keeping the plunger sensor is important to you. The older VirtuaPin plunger kits came with different IR sensors that the Pinscape software doesn't handle.)

Wed Sep 23 05:06:39 2015 +0000
Initial TLC5940 PWM controller chip support.

Who changed what in which revision?

UserRevisionLine numberNew contents of line
mjr 26:cb71c4af2912 1 // Pinscape Controller TLC5940 interface
mjr 26:cb71c4af2912 2 //
mjr 26:cb71c4af2912 3 // Based on Spencer Davis's mbed TLC5940 library. Adapted for the
mjr 26:cb71c4af2912 4 // KL25Z, and simplified to just the functions needed for this
mjr 26:cb71c4af2912 5 // application. In particular, this version doesn't include support
mjr 26:cb71c4af2912 6 // for dot correction programming or status input. This version also
mjr 26:cb71c4af2912 7 // uses a different approach for sending the grayscale data updates,
mjr 26:cb71c4af2912 8 // sending updates during the blanking interval rather than overlapping
mjr 26:cb71c4af2912 9 // them with the PWM cycle. This results in very slightly longer
mjr 26:cb71c4af2912 10 // blanking intervals when updates are pending, effectively reducing
mjr 26:cb71c4af2912 11 // the PWM "on" duty cycle (and thus the output brightness) by about
mjr 26:cb71c4af2912 12 // 0.3%. This shouldn't be perceptible to users, so it's a small
mjr 26:cb71c4af2912 13 // trade-off for the advantage gained, which is much better signal
mjr 26:cb71c4af2912 14 // stability when using multiple TLC5940s daisy-chained together.
mjr 26:cb71c4af2912 15 // I saw a lot of instability when using the overlapped approach,
mjr 26:cb71c4af2912 16 // which seems to be eliminated entirely when sending updates during
mjr 26:cb71c4af2912 17 // the blanking interval.
mjr 26:cb71c4af2912 18
mjr 26:cb71c4af2912 19
mjr 26:cb71c4af2912 20 #ifndef TLC5940_H
mjr 26:cb71c4af2912 21 #define TLC5940_H
mjr 26:cb71c4af2912 22
mjr 26:cb71c4af2912 23 #include "mbed.h"
mjr 26:cb71c4af2912 24 #include "FastPWM.h"
mjr 26:cb71c4af2912 25
mjr 26:cb71c4af2912 26 /**
mjr 26:cb71c4af2912 27 * SPI speed used by the mbed to communicate with the TLC5940
mjr 26:cb71c4af2912 28 * The TLC5940 supports up to 30Mhz. It's best to keep this as
mjr 26:cb71c4af2912 29 * high as the microcontroller will allow, since a higher SPI
mjr 26:cb71c4af2912 30 * speed yields a faster grayscale data update. However, if
mjr 26:cb71c4af2912 31 * you have problems with unreliable signal transmission to the
mjr 26:cb71c4af2912 32 * TLC5940s, reducing this speed might help.
mjr 26:cb71c4af2912 33 *
mjr 26:cb71c4af2912 34 * The SPI clock must be fast enough that the data transmission
mjr 26:cb71c4af2912 35 * time for a full update is comfortably less than the blanking
mjr 26:cb71c4af2912 36 * cycle time. The grayscale refresh requires 192 bits per TLC5940
mjr 26:cb71c4af2912 37 * in the daisy chain, and each bit takes one SPI clock to send.
mjr 26:cb71c4af2912 38 * Our reference setup in the Pinscape controller allows for up to
mjr 26:cb71c4af2912 39 * 4 TLC5940s, so a full refresh cycle on a fully populated system
mjr 26:cb71c4af2912 40 * would be 768 SPI clocks. The blanking cycle is 4096 GSCLK cycles.
mjr 26:cb71c4af2912 41 *
mjr 26:cb71c4af2912 42 * t(blank) = 4096 * 1/GSCLK_SPEED
mjr 26:cb71c4af2912 43 * t(refresh) = 768 * 1/SPI_SPEED
mjr 26:cb71c4af2912 44 * Therefore: SPI_SPEED must be > 768/4096 * GSCLK_SPEED
mjr 26:cb71c4af2912 45 *
mjr 26:cb71c4af2912 46 * Since the SPI speed can be so high, and since we want to keep
mjr 26:cb71c4af2912 47 * the GSCLK speed relatively low, the constraint above simply
mjr 26:cb71c4af2912 48 * isn't a factor. E.g., at SPI=30MHz and GSCLK=500kHz,
mjr 26:cb71c4af2912 49 * t(blank) is 8192us and t(refresh) is 25us.
mjr 26:cb71c4af2912 50 */
mjr 26:cb71c4af2912 51 #define SPI_SPEED 3000000
mjr 26:cb71c4af2912 52
mjr 26:cb71c4af2912 53 /**
mjr 26:cb71c4af2912 54 * The rate at which the GSCLK pin is pulsed. This also controls
mjr 26:cb71c4af2912 55 * how often the reset function is called. The reset function call
mjr 26:cb71c4af2912 56 * rate is (1/GSCLK_SPEED) * 4096. The maximum reliable rate is
mjr 26:cb71c4af2912 57 * around 32Mhz. It's best to keep this rate as low as possible:
mjr 26:cb71c4af2912 58 * the higher the rate, the higher the refresh() call frequency,
mjr 26:cb71c4af2912 59 * so the higher the CPU load.
mjr 26:cb71c4af2912 60 *
mjr 26:cb71c4af2912 61 * The lower bound is probably dependent on the application. For
mjr 26:cb71c4af2912 62 * driving LEDs, the limiting factor is that lower rates will increase
mjr 26:cb71c4af2912 63 * visible flicker. 200 kHz seems to be a good lower bound for LEDs.
mjr 26:cb71c4af2912 64 * That provides about 48 cycles per second - that's about the same as
mjr 26:cb71c4af2912 65 * the 50 Hz A/C cycle rate in many countries, which was itself chosen
mjr 26:cb71c4af2912 66 * so that incandescent lights don't flicker. (This rate is a function
mjr 26:cb71c4af2912 67 * of human eye physiology, which has its own refresh cycle of sorts
mjr 26:cb71c4af2912 68 * that runs at about 50 Hz. If you're designing an LED system for
mjr 26:cb71c4af2912 69 * viewing by cats or drosophila, you might want to look into your
mjr 26:cb71c4af2912 70 * target species' eye physiology, since the persistence of vision
mjr 26:cb71c4af2912 71 * rate varies quite a bit from species to species.) Flicker tends to
mjr 26:cb71c4af2912 72 * be more noticeable in LEDs than in incandescents, since LEDs don't
mjr 26:cb71c4af2912 73 * have the thermal inertia of incandescents, so we use a slightly
mjr 26:cb71c4af2912 74 * higher default here. 500 kHz = 122 full grayscale cycles per
mjr 26:cb71c4af2912 75 * second = 122 reset calls per second (call every 8ms).
mjr 26:cb71c4af2912 76 */
mjr 26:cb71c4af2912 77 #define GSCLK_SPEED 500000
mjr 26:cb71c4af2912 78
mjr 26:cb71c4af2912 79 /**
mjr 26:cb71c4af2912 80 * This class controls a TLC5940 PWM driver IC.
mjr 26:cb71c4af2912 81 *
mjr 26:cb71c4af2912 82 * Using the TLC5940 class to control an LED:
mjr 26:cb71c4af2912 83 * @code
mjr 26:cb71c4af2912 84 * #include "mbed.h"
mjr 26:cb71c4af2912 85 * #include "TLC5940.h"
mjr 26:cb71c4af2912 86 *
mjr 26:cb71c4af2912 87 * // Create the TLC5940 instance
mjr 26:cb71c4af2912 88 * TLC5940 tlc(p7, p5, p21, p9, p10, p11, p12, 1);
mjr 26:cb71c4af2912 89 *
mjr 26:cb71c4af2912 90 * int main()
mjr 26:cb71c4af2912 91 * {
mjr 26:cb71c4af2912 92 * // Enable the first LED
mjr 26:cb71c4af2912 93 * tlc.set(0, 0xfff);
mjr 26:cb71c4af2912 94 *
mjr 26:cb71c4af2912 95 * while(1)
mjr 26:cb71c4af2912 96 * {
mjr 26:cb71c4af2912 97 * }
mjr 26:cb71c4af2912 98 * }
mjr 26:cb71c4af2912 99 * @endcode
mjr 26:cb71c4af2912 100 */
mjr 26:cb71c4af2912 101 class TLC5940
mjr 26:cb71c4af2912 102 {
mjr 26:cb71c4af2912 103 public:
mjr 26:cb71c4af2912 104 /**
mjr 26:cb71c4af2912 105 * Set up the TLC5940
mjr 26:cb71c4af2912 106 * @param SCLK - The SCK pin of the SPI bus
mjr 26:cb71c4af2912 107 * @param MOSI - The MOSI pin of the SPI bus
mjr 26:cb71c4af2912 108 * @param GSCLK - The GSCLK pin of the TLC5940(s)
mjr 26:cb71c4af2912 109 * @param BLANK - The BLANK pin of the TLC5940(s)
mjr 26:cb71c4af2912 110 * @param XLAT - The XLAT pin of the TLC5940(s)
mjr 26:cb71c4af2912 111 * @param nchips - The number of TLC5940s (if you are daisy chaining)
mjr 26:cb71c4af2912 112 */
mjr 26:cb71c4af2912 113 TLC5940(PinName SCLK, PinName MOSI, PinName GSCLK, PinName BLANK, PinName XLAT, int nchips)
mjr 26:cb71c4af2912 114 : spi(MOSI, NC, SCLK),
mjr 26:cb71c4af2912 115 gsclk(GSCLK),
mjr 26:cb71c4af2912 116 blank(BLANK),
mjr 26:cb71c4af2912 117 xlat(XLAT),
mjr 26:cb71c4af2912 118 nchips(nchips),
mjr 26:cb71c4af2912 119 newGSData(false)
mjr 26:cb71c4af2912 120 {
mjr 26:cb71c4af2912 121 // allocate the grayscale buffer
mjr 26:cb71c4af2912 122 gs = new unsigned short[nchips*16];
mjr 26:cb71c4af2912 123
mjr 26:cb71c4af2912 124 // Configure SPI format and speed. Note that KL25Z ONLY supports 8-bit
mjr 26:cb71c4af2912 125 // mode. The TLC5940 nominally requires 12-bit data blocks for the
mjr 26:cb71c4af2912 126 // grayscale levels, but SPI is ultimately just a bit-level serial format,
mjr 26:cb71c4af2912 127 // so we can reformat the 12-bit blocks into 8-bit bytes to fit the
mjr 26:cb71c4af2912 128 // KL25Z's limits. This should work equally well on other microcontrollers
mjr 26:cb71c4af2912 129 // that are more flexible. The TLC5940 appears to require polarity/phase
mjr 26:cb71c4af2912 130 // format 0.
mjr 26:cb71c4af2912 131 spi.format(8, 0);
mjr 26:cb71c4af2912 132 spi.frequency(SPI_SPEED);
mjr 26:cb71c4af2912 133
mjr 26:cb71c4af2912 134 // Set output pin states
mjr 26:cb71c4af2912 135 xlat = 0;
mjr 26:cb71c4af2912 136 blank = 1;
mjr 26:cb71c4af2912 137
mjr 26:cb71c4af2912 138 // Configure PWM output for GSCLK frequency at 50% duty cycle
mjr 26:cb71c4af2912 139 gsclk.period(1.0/GSCLK_SPEED);
mjr 26:cb71c4af2912 140 gsclk.write(.5);
mjr 26:cb71c4af2912 141 blank = 0;
mjr 26:cb71c4af2912 142
mjr 26:cb71c4af2912 143 // Set up the first call to the reset function, which asserts BLANK to
mjr 26:cb71c4af2912 144 // end the PWM cycle and handles new grayscale data output and latching.
mjr 26:cb71c4af2912 145 // The original version of this library uses a timer to call reset
mjr 26:cb71c4af2912 146 // periodically, but that approach is somewhat problematic because the
mjr 26:cb71c4af2912 147 // reset function itself takes a small amount of time to run, so the
mjr 26:cb71c4af2912 148 // *actual* cycle is slightly longer than what we get from counting
mjr 26:cb71c4af2912 149 // GS clocks. Running reset on a timer therefore causes the calls to
mjr 26:cb71c4af2912 150 // slip out of phase with the actual full cycles, which causes
mjr 26:cb71c4af2912 151 // premature blanking that shows up as visible flicker. To get the
mjr 26:cb71c4af2912 152 // reset cycle to line up exactly with a full PWM cycle, it works
mjr 26:cb71c4af2912 153 // better to set up a new timer on each cycle, *after* we've finished
mjr 26:cb71c4af2912 154 // with the somewhat unpredictable overhead of the interrupt handler.
mjr 26:cb71c4af2912 155 // This ensures that we'll get much closer to exact alignment of the
mjr 26:cb71c4af2912 156 // cycle phase, and in any case the worst that happens is that some
mjr 26:cb71c4af2912 157 // cycles are very slightly too long or short (due to imperfections
mjr 26:cb71c4af2912 158 // in the timer clock vs the PWM clock that determines the GSCLCK
mjr 26:cb71c4af2912 159 // output to the TLC5940), which is far less noticeable than a
mjr 26:cb71c4af2912 160 // constantly rotating phase misalignment.
mjr 26:cb71c4af2912 161 reset_timer.attach(this, &TLC5940::reset, (1.0/GSCLK_SPEED)*4096.0);
mjr 26:cb71c4af2912 162 }
mjr 26:cb71c4af2912 163
mjr 26:cb71c4af2912 164 ~TLC5940()
mjr 26:cb71c4af2912 165 {
mjr 26:cb71c4af2912 166 delete [] gs;
mjr 26:cb71c4af2912 167 }
mjr 26:cb71c4af2912 168
mjr 26:cb71c4af2912 169 /**
mjr 26:cb71c4af2912 170 * Set the next chunk of grayscale data to be sent
mjr 26:cb71c4af2912 171 * @param data - Array of 16 bit shorts containing 16 12 bit grayscale data chunks per TLC5940
mjr 26:cb71c4af2912 172 * @note These must be in intervals of at least (1/GSCLK_SPEED) * 4096 to be sent
mjr 26:cb71c4af2912 173 */
mjr 26:cb71c4af2912 174 void set(int idx, unsigned short data)
mjr 26:cb71c4af2912 175 {
mjr 26:cb71c4af2912 176 // store the data, and flag the pending update for the interrupt handler to carry out
mjr 26:cb71c4af2912 177 gs[idx] = data;
mjr 26:cb71c4af2912 178 newGSData = true;
mjr 26:cb71c4af2912 179 }
mjr 26:cb71c4af2912 180
mjr 26:cb71c4af2912 181 private:
mjr 26:cb71c4af2912 182 // current level for each output
mjr 26:cb71c4af2912 183 unsigned short *gs;
mjr 26:cb71c4af2912 184
mjr 26:cb71c4af2912 185 // SPI port - only MOSI and SCK are used
mjr 26:cb71c4af2912 186 SPI spi;
mjr 26:cb71c4af2912 187
mjr 26:cb71c4af2912 188 // use a PWM out for the grayscale clock - this provides a stable
mjr 26:cb71c4af2912 189 // square wave signal without consuming CPU
mjr 26:cb71c4af2912 190 FastPWM gsclk;
mjr 26:cb71c4af2912 191
mjr 26:cb71c4af2912 192 // Digital out pins used for the TLC5940
mjr 26:cb71c4af2912 193 DigitalOut blank;
mjr 26:cb71c4af2912 194 DigitalOut xlat;
mjr 26:cb71c4af2912 195
mjr 26:cb71c4af2912 196 // number of daisy-chained TLC5940s we're controlling
mjr 26:cb71c4af2912 197 int nchips;
mjr 26:cb71c4af2912 198
mjr 26:cb71c4af2912 199 // Timeout to end each PWM cycle. This is a one-shot timer that we reset
mjr 26:cb71c4af2912 200 // on each cycle.
mjr 26:cb71c4af2912 201 Timeout reset_timer;
mjr 26:cb71c4af2912 202
mjr 26:cb71c4af2912 203 // Has new GS/DC data been loaded?
mjr 26:cb71c4af2912 204 volatile bool newGSData;
mjr 26:cb71c4af2912 205
mjr 26:cb71c4af2912 206 // Function to reset the display and send the next chunks of data
mjr 26:cb71c4af2912 207 void reset()
mjr 26:cb71c4af2912 208 {
mjr 26:cb71c4af2912 209 // turn off the grayscale clock, and assert BLANK to end the grayscale cycle
mjr 26:cb71c4af2912 210 gsclk.write(0);
mjr 26:cb71c4af2912 211 blank = 1;
mjr 26:cb71c4af2912 212
mjr 26:cb71c4af2912 213 // If we have new GS data, send it now
mjr 26:cb71c4af2912 214 if (newGSData)
mjr 26:cb71c4af2912 215 {
mjr 26:cb71c4af2912 216 // Send the new grayscale data.
mjr 26:cb71c4af2912 217 //
mjr 26:cb71c4af2912 218 // Note that ideally, we'd do this during the new PWM cycle
mjr 26:cb71c4af2912 219 // rather than during the blanking interval. The TLC5940 is
mjr 26:cb71c4af2912 220 // specifically designed to allow this. However, in my testing,
mjr 26:cb71c4af2912 221 // I found that sending new data during the PWM cycle was
mjr 26:cb71c4af2912 222 // unreliable - it seemed to cause a fair amount of glitching,
mjr 26:cb71c4af2912 223 // which as far as I can tell is signal noise coming from
mjr 26:cb71c4af2912 224 // crosstalk between the grayscale clock signal and the
mjr 26:cb71c4af2912 225 // SPI signal. This seems to be a common problem with
mjr 26:cb71c4af2912 226 // daisy-chained TLC5940s. It can in principle be solved with
mjr 26:cb71c4af2912 227 // careful high-speed circuit design (good ground planes,
mjr 26:cb71c4af2912 228 // short leads, decoupling capacitors), and indeed I was able
mjr 26:cb71c4af2912 229 // to improve stability to some extent with circuit tweaks,
mjr 26:cb71c4af2912 230 // but I wasn't able to eliminate it entirely. Moving the
mjr 26:cb71c4af2912 231 // data refresh into the blanking interval, on the other
mjr 26:cb71c4af2912 232 // hand, seems to entirely eliminate any instability.
mjr 26:cb71c4af2912 233 //
mjr 26:cb71c4af2912 234 // Note that there's no CPU performance penalty to this
mjr 26:cb71c4af2912 235 // approach. The KL25Z SPI implementation isn't capable of
mjr 26:cb71c4af2912 236 // asynchronous DMA, so the CPU has to wait for the
mjr 26:cb71c4af2912 237 // transmission no matter when it happens. The only downside
mjr 26:cb71c4af2912 238 // I see to this approach is that it decreases the duty cycle
mjr 26:cb71c4af2912 239 // of the PWM during updates - but very slightly. With the
mjr 26:cb71c4af2912 240 // SPI clock at 30 MHz and the PWM clock at 500 kHz, the full
mjr 26:cb71c4af2912 241 // PWM cycle is 8192us, and the data refresh time is 25us.
mjr 26:cb71c4af2912 242 // So by doing the data refersh in the blanking interval,
mjr 26:cb71c4af2912 243 // we're effectively extending the PWM cycle to 8217us,
mjr 26:cb71c4af2912 244 // which is 0.3% longer. Since the outputs are all off
mjr 26:cb71c4af2912 245 // during the blanking cycle, this is equivalent to
mjr 26:cb71c4af2912 246 // decreasing all of the output brightnesses by 0.3%. That
mjr 26:cb71c4af2912 247 // should be imperceptible to users.
mjr 26:cb71c4af2912 248 update();
mjr 26:cb71c4af2912 249
mjr 26:cb71c4af2912 250 // the chips are now in sync with our data, so we have no more
mjr 26:cb71c4af2912 251 // pending update
mjr 26:cb71c4af2912 252 newGSData = false;
mjr 26:cb71c4af2912 253
mjr 26:cb71c4af2912 254 // latch the new data while we're still blanked
mjr 26:cb71c4af2912 255 xlat = 1;
mjr 26:cb71c4af2912 256 xlat = 0;
mjr 26:cb71c4af2912 257 }
mjr 26:cb71c4af2912 258
mjr 26:cb71c4af2912 259 // end the blanking interval and restart the grayscale clock
mjr 26:cb71c4af2912 260 blank = 0;
mjr 26:cb71c4af2912 261 gsclk.write(.5);
mjr 26:cb71c4af2912 262
mjr 26:cb71c4af2912 263 // set up the next blanking interrupt
mjr 26:cb71c4af2912 264 reset_timer.attach(this, &TLC5940::reset, (1.0/GSCLK_SPEED)*4096.0);
mjr 26:cb71c4af2912 265 }
mjr 26:cb71c4af2912 266
mjr 26:cb71c4af2912 267 void update()
mjr 26:cb71c4af2912 268 {
mjr 26:cb71c4af2912 269 // Send GS data. The serial format orders the outputs from last to first
mjr 26:cb71c4af2912 270 // (output #15 on the last chip in the daisy-chain to output #0 on the
mjr 26:cb71c4af2912 271 // first chip). For each output, we send 12 bits containing the grayscale
mjr 26:cb71c4af2912 272 // level (0 = fully off, 0xFFF = fully on). Bit order is most significant
mjr 26:cb71c4af2912 273 // bit first.
mjr 26:cb71c4af2912 274 //
mjr 26:cb71c4af2912 275 // The KL25Z SPI can only send in 8-bit increments, so we need to divvy up
mjr 26:cb71c4af2912 276 // the 12-bit outputs into 8-bit bytes. Each pair of 12-bit outputs adds up
mjr 26:cb71c4af2912 277 // to 24 bits, which divides evenly into 3 bytes, so send each pairs of
mjr 26:cb71c4af2912 278 // outputs as three bytes:
mjr 26:cb71c4af2912 279 //
mjr 26:cb71c4af2912 280 // [ element i+1 bits ] [ element i bits ]
mjr 26:cb71c4af2912 281 // 11 10 9 8 7 6 5 4 3 2 1 0 11 10 9 8 7 6 5 4 3 2 1 0
mjr 26:cb71c4af2912 282 // [ first byte ] [ second byte ] [ third byte ]
mjr 26:cb71c4af2912 283 for (int i = (16 * nchips) - 2 ; i >= 0 ; i -= 2)
mjr 26:cb71c4af2912 284 {
mjr 26:cb71c4af2912 285 // first byte - element i+1 bits 4-11
mjr 26:cb71c4af2912 286 spi.write(((gs[i+1] & 0xFF0) >> 4) & 0xff);
mjr 26:cb71c4af2912 287
mjr 26:cb71c4af2912 288 // second byte - element i+1 bits 0-3, then element i bits 8-11
mjr 26:cb71c4af2912 289 spi.write((((gs[i+1] & 0x00F) << 4) | ((gs[i] & 0xF00) >> 8)) & 0xFF);
mjr 26:cb71c4af2912 290
mjr 26:cb71c4af2912 291 // third byte - element i bits 0-7
mjr 26:cb71c4af2912 292 spi.write(gs[i] & 0x0FF);
mjr 26:cb71c4af2912 293 }
mjr 26:cb71c4af2912 294 }
mjr 26:cb71c4af2912 295 };
mjr 26:cb71c4af2912 296
mjr 26:cb71c4af2912 297
mjr 26:cb71c4af2912 298 #endif