An I/O controller for virtual pinball machines: accelerometer nudge sensing, analog plunger input, button input encoding, LedWiz compatible output controls, and more.
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This is Version 2 of the Pinscape Controller, an I/O controller for virtual pinball machines. (You can find the old version 1 software here.) Pinscape is software for the KL25Z that turns the board into a full-featured I/O controller for virtual pinball, with support for accelerometer-based nudging, a real plunger, button inputs, and feedback device control.
In case you haven't heard of the concept before, a "virtual pinball machine" is basically a video pinball simulator that's built into a real pinball machine body. A TV monitor goes in place of the pinball playfield, and a second TV goes in the backbox to serve as the "backglass" display. A third smaller monitor can serve as the "DMD" (the Dot Matrix Display used for scoring on newer machines), or you can even install a real pinball plasma DMD. A computer is hidden inside the cabinet, running pinball emulation software that displays a life-sized playfield on the main TV. The cabinet has all of the usual buttons, too, so it not only looks like the real thing, but plays like it too. That's a picture of my own machine to the right. On the outside, it's built exactly like a real arcade pinball machine, with the same overall dimensions and all of the standard pinball cabinet hardware.
A few small companies build and sell complete, finished virtual pinball machines, but I think it's more fun as a DIY project. If you have some basic wood-working skills and know your way around PCs, you can build one from scratch. The computer part is just an ordinary Windows PC, and all of the pinball emulation can be built out of free, open-source software. In that spirit, the Pinscape Controller is an open-source software/hardware project that offers a no-compromises, all-in-one control center for all of the unique input/output needs of a virtual pinball cabinet. If you've been thinking about building one of these, but you're not sure how to connect a plunger, flipper buttons, lights, nudge sensor, and whatever else you can think of, this project might be just what you're looking for.
You can find much more information about DIY Pin Cab building in general in the Virtual Cabinet Forum on vpforums.org. Also visit my Pinscape Resources page for more about this project and other virtual pinball projects I'm working on.
- 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).
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.
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.
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.
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.
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.
- Custom VP builds: I created modified versions of Visual Pinball 9.9 and Physmod5 that you might want to use in combination with this controller. The modified versions have special handling for plunger calibration specific to the Pinscape Controller, as well as some enhancements to the nudge physics. If you're not using the plunger, you might still want it for the nudge improvements. The modified version also works with any other input controller, so you can get the enhanced nudging effects even if you're using a different plunger/nudge kit. The big change in the modified versions is a "filter" for accelerometer input that's designed to make the response to cabinet nudges more realistic. It also makes the response more subdued than in the standard VP, so it's not to everyone's taste. The downloads include both the updated executables and the source code changes, in case you want to merge the changes into your own custom version(s).
Note! These features are now standard in the official VP releases, so you don't need my custom builds if you're using 9.9.1 or later and/or VP 10. I don't think there's any reason to use my versions instead of the latest official ones, and in fact I'd encourage you to use the official releases since they're more up to date, but I'm leaving my builds available just in case. In the official versions, look for the checkbox "Enable Nudge Filter" in the Keys preferences dialog. My custom versions don't include that checkbox; they just enable the filter unconditionally.
- Output circuit shopping list: This is a saved shopping cart at mouser.com with the parts needed to build one copy of the high-power output circuit for the LedWiz emulator feature, for use with the standalone KL25Z (that is, without the expansion boards). The quantities in the cart are for one output channel, so if you want N outputs, simply multiply the quantities by the N, with one exception: you only need one ULN2803 transistor array chip for each eight output circuits. If you're using the expansion boards, you won't need any of this, since the boards provide their own high-power outputs.
- Cary Owens' optical sensor housing: A 3D-printable design for a housing/mounting bracket for the optical plunger sensor, designed by Cary Owens. This makes it easy to mount the sensor.
- Lemming77's potentiometer mounting bracket and shooter rod connecter: Sketchup designs for 3D-printable parts for mounting a slide potentiometer as the plunger sensor. These were designed for a particular slide potentiometer that used to be available from an Aliexpress.com seller but is no longer listed. You can probably use this design as a starting point for other similar devices; just check the dimensions before committing the design to plastic.
Copyright and License
The Pinscape firmware is copyright 2014, 2021 by Michael J Roberts. It's released under an MIT open-source license. See License.
Warning to VirtuaPin Kit Owners
This software isn't designed as a replacement for the VirtuaPin plunger kit's firmware. If you bought the VirtuaPin kit, I recommend that you don't install this software. The 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.)
TLC5940/TLC5940.h@26:cb71c4af2912, 2015-09-23 (annotated)
- Wed Sep 23 05:06:39 2015 +0000
Initial TLC5940 PWM controller chip support.
Who changed what in which revision?
|User||Revision||Line number||New contents of line|
|mjr||26:cb71c4af2912||1||// Pinscape Controller TLC5940 interface|
|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||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||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||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||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||51||#define SPI_SPEED 3000000|
|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||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||77||#define GSCLK_SPEED 500000|
|mjr||26:cb71c4af2912||80||* This class controls a TLC5940 PWM driver IC.|
|mjr||26:cb71c4af2912||82||* Using the TLC5940 class to control an LED:|
|mjr||26:cb71c4af2912||84||* #include "mbed.h"|
|mjr||26:cb71c4af2912||85||* #include "TLC5940.h"|
|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||90||* int main()|
|mjr||26:cb71c4af2912||92||* // Enable the first LED|
|mjr||26:cb71c4af2912||93||* tlc.set(0, 0xfff);|
|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||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||121||// allocate the grayscale buffer|
|mjr||26:cb71c4af2912||122||gs = new unsigned short[nchips*16];|
|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||134||// Set output pin states|
|mjr||26:cb71c4af2912||135||xlat = 0;|
|mjr||26:cb71c4af2912||136||blank = 1;|
|mjr||26:cb71c4af2912||138||// Configure PWM output for GSCLK frequency at 50% duty cycle|
|mjr||26:cb71c4af2912||141||blank = 0;|
|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||166||delete  gs;|
|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||174||void set(int idx, unsigned short data)|
|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||182||// current level for each output|
|mjr||26:cb71c4af2912||183||unsigned short *gs;|
|mjr||26:cb71c4af2912||185||// SPI port - only MOSI and SCK are used|
|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||192||// Digital out pins used for the TLC5940|
|mjr||26:cb71c4af2912||196||// number of daisy-chained TLC5940s we're controlling|
|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||203||// Has new GS/DC data been loaded?|
|mjr||26:cb71c4af2912||204||volatile bool newGSData;|
|mjr||26:cb71c4af2912||206||// Function to reset the display and send the next chunks of data|
|mjr||26:cb71c4af2912||209||// turn off the grayscale clock, and assert BLANK to end the grayscale cycle|
|mjr||26:cb71c4af2912||211||blank = 1;|
|mjr||26:cb71c4af2912||213||// If we have new GS data, send it now|
|mjr||26:cb71c4af2912||216||// Send the new grayscale data.|
|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||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||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||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||259||// end the blanking interval and restart the grayscale clock|
|mjr||26:cb71c4af2912||260||blank = 0;|
|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||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||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||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||285||// first byte - element i+1 bits 4-11|
|mjr||26:cb71c4af2912||286||spi.write(((gs[i+1] & 0xFF0) >> 4) & 0xff);|
|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||291||// third byte - element i bits 0-7|
|mjr||26:cb71c4af2912||292||spi.write(gs[i] & 0x0FF);|