An I/O controller for virtual pinball machines: accelerometer nudge sensing, analog plunger input, button input encoding, LedWiz compatible output controls, and more.

Dependencies:   mbed FastIO FastPWM USBDevice

Fork of Pinscape_Controller by Mike R


This is Version 2 of the Pinscape Controller, an I/O controller for virtual pinball machines. (You can find the old version 1 software here.) Pinscape is software for the KL25Z that turns the board into a full-featured I/O controller for virtual pinball, with support for accelerometer-based nudging, a real plunger, button inputs, and feedback device control.

In case you haven't heard of the concept before, a "virtual pinball machine" is basically a video pinball simulator that's built into a real pinball machine body. A TV monitor goes in place of the pinball playfield, and a second TV goes in the backbox to serve as the "backglass" display. A third smaller monitor can serve as the "DMD" (the Dot Matrix Display used for scoring on newer machines), or you can even install a real pinball plasma DMD. A computer is hidden inside the cabinet, running pinball emulation software that displays a life-sized playfield on the main TV. The cabinet has all of the usual buttons, too, so it not only looks like the real thing, but plays like it too. That's a picture of my own machine to the right. On the outside, it's built exactly like a real arcade pinball machine, with the same overall dimensions and all of the standard pinball cabinet hardware.

A few small companies build and sell complete, finished virtual pinball machines, but I think it's more fun as a DIY project. If you have some basic wood-working skills and know your way around PCs, you can build one from scratch. The computer part is just an ordinary Windows PC, and all of the pinball emulation can be built out of free, open-source software. In that spirit, the Pinscape Controller is an open-source software/hardware project that offers a no-compromises, all-in-one control center for all of the unique input/output needs of a virtual pinball cabinet. If you've been thinking about building one of these, but you're not sure how to connect a plunger, flipper buttons, lights, nudge sensor, and whatever else you can think of, this project might be just what you're looking for.

You can find much more information about DIY Pin Cab building in general in the Virtual Cabinet Forum on Also visit my Pinscape Resources page for more about this project and other virtual pinball projects I'm working on.


  • Pinscape Release Builds: This page has download links for all of the Pinscape software. To get started, install and run the Pinscape Config Tool on your Windows computer. It will lead you through the steps for installing the Pinscape firmware on the KL25Z.
  • Config Tool Source Code. The complete C# source code for the config tool. You don't need this to run the tool, but it's available if you want to customize anything or see how it works inside.


The new Version 2 Build Guide is now complete! This new version aims to be a complete guide to building a virtual pinball machine, including not only the Pinscape elements but all of the basics, from sourcing parts to building all of the hardware.

You can also refer to the original Hardware Build Guide (PDF), but that's out of date now, since it refers to the old version 1 software, which was rather different (especially when it comes to configuration).

System Requirements

The new config tool requires a fairly up-to-date Microsoft .NET installation. If you use Windows Update to keep your system current, you should be fine. A modern version of Internet Explorer (IE) is required, even if you don't use it as your main browser, because the config tool uses some system components that Microsoft packages into the IE install set. I test with IE11, so that's known to work. IE8 doesn't work. IE9 and 10 are unknown at this point.

The Windows requirements are only for the config tool. The firmware doesn't care about anything on the Windows side, so if you can make do without the config tool, you can use almost any Windows setup.

Main Features

Plunger: The Pinscape Controller started out as a "mechanical plunger" controller: a device for attaching a real pinball plunger to the video game software so that you could launch the ball the natural way. This is still, of course, a central feature of the project. The software supports several types of sensors: a high-resolution optical sensor (which works by essentially taking pictures of the plunger as it moves); a slide potentionmeter (which determines the position via the changing electrical resistance in the pot); a quadrature sensor (which counts bars printed on a special guide rail that it moves along); and an IR distance sensor (which determines the position by sending pulses of light at the plunger and measuring the round-trip travel time). The Build Guide explains how to set up each type of sensor.

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

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

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

Expansion Boards

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

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

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

Expansion Board project page

Update notes

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

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

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

New Features

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

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

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

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

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

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

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

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

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

More Downloads

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

    Note! These features are now standard in the official VP releases, so you don't need my custom builds if you're using 9.9.1 or later and/or VP 10. I don't think there's any reason to use my versions instead of the latest official ones, and in fact I'd encourage you to use the official releases since they're more up to date, but I'm leaving my builds available just in case. In the official versions, look for the checkbox "Enable Nudge Filter" in the Keys preferences dialog. My custom versions don't include that checkbox; they just enable the filter unconditionally.
  • Output circuit shopping list: This is a saved shopping cart at with the parts needed to build one copy of the high-power output circuit for the LedWiz emulator feature, for use with the standalone KL25Z (that is, without the expansion boards). The quantities in the cart are for one output channel, so if you want N outputs, simply multiply the quantities by the N, with one exception: you only need one ULN2803 transistor array chip for each eight output circuits. If you're using the expansion boards, you won't need any of this, since the boards provide their own high-power outputs.
  • Cary Owens' optical sensor housing: A 3D-printable design for a housing/mounting bracket for the optical plunger sensor, designed by Cary Owens. This makes it easy to mount the sensor.
  • Lemming77's potentiometer mounting bracket and shooter rod connecter: Sketchup designs for 3D-printable parts for mounting a slide potentiometer as the plunger sensor. These were designed for a particular slide potentiometer that used to be available from an seller but is no longer listed. You can probably use this design as a starting point for other similar devices; just check the dimensions before committing the design to plastic.

Copyright and License

The Pinscape firmware is copyright 2014, 2021 by Michael J Roberts. It's released under an MIT open-source license. See License.

Warning to VirtuaPin Kit Owners

This software isn't designed as a replacement for the VirtuaPin plunger kit's firmware. If you bought the VirtuaPin kit, I recommend that you don't install this software. The VirtuaPin kit uses the same KL25Z microcontroller that Pinscape uses, but the rest of its hardware is different and incompatible. In particular, the Pinscape firmware doesn't include support for the IR proximity sensor used in the VirtuaPin plunger kit, so you won't be able to use your plunger device with the Pinscape firmware. In addition, the VirtuaPin setup uses a different set of GPIO pins for the button inputs from the Pinscape defaults, so if you do install the Pinscape firmware, you'll have to go into the Config Tool and reassign all of the buttons to match the VirtuaPin wiring.


12 months ago

File content as of revision 109:310ac82cbbee:

 *  AMS/TAOS TSL14xx series photodiode array interface class.
 *  This provides a high-level interface for the AMS/TAOS TSLxx series
 *  of photodiode arrays.  This class works with most of the sensors
 *  in this series, which differ only in pixel array sizes.  This code
 *  has been tested with the following sensors from the series:
 *  TSL1410R  - 1280 pixels, 400dpi
 *  TSL1412S  - 1536 pixels, 400dpi
 *  TSL1401CL - 128 pixels, 400dpi
 *  All of these sensors have the same electrical interface, consisting
 *  of a clock input (CLK), start pulse input (SI), and analog pixel
 *  output (AO).  The sensors are equipped with hold capacitors and
 *  shift registers that allow simultaneous sampling of all pixels, and
 *  serial access to the pixel values.
 *  (Note on the plunger sensor class hierarchy: this class is for the
 *  sensor only, not for the plunger application.  This class is meant
 *  to be reusable in other contexts that just need to read raw pixel
 *  data from the sensor.  Plunger/tslxxSensor.h implements the 
 *  specializations of the plunger interface class for these sensors.)
 *  *** Double buffering ***
 *  Our API is based on a double-buffered asynchronous read.  The caller
 *  can access a completed buffer, containing the pixels from the last image 
 *  frame, while the sensor is transferring data asynchronously (using the 
 *  microcontroller's DMA capability) into the other buffer.  Each time a
 *  new read is started, we swap buffers, making the last completed buffer 
 *  available to the client and handing the other buffer to the DMA
 *  controller to fill asynchronously.
 *  In a way, there are actually THREE frames in our pipeline at any given
 *  time:
 *   - a live image integrating light on the photo receptors on the sensor
 *   - the prior image, held in the sensor's shift register and being 
 *     transferred via DMA into one of our buffers (the "DMA" buffer)
 *   - the second prior image, in our other buffer (the "stable" buffer),
 *     available for the client to process
 *  The integration process on the sensor starts when we begin the transfer
 *  of an image via DMA.  That frame's integration period ends when the next 
 *  transfer starts.  So the minimum integration time is also the DMA pixel
 *  transfer time.  Longer integration times can be achieved by waiting
 *  for an additional interval after a DMA transfer finishes, before starting
 *  the next transfer.  We make provision for this added time to allow for
 *  longer exposure times to optimize image quality.
 *  *** Optimizing pixel transfer speed ***
 *  For Pinscape purposes, we want the fastest possible frame rate, as we're
 *  trying to accurately capture the motion of a fast-moving object (the 
 *  plunger).  The TSL14xx sensors can achieve a frame rate up to about
 *  1000 frames per second, if everything is clocked at the limits in the
 *  data sheet.  The KL25Z, however, can't achieve that fast a rate.  The
 *  limiting factor is the KL25Z's ADC.  We have to take an ADC sample for
 *  every pixel, and the minimum sampling time for the ADC on the KL25Z is
 *  about 2us.  With the 1280-pixel TSL1410R, that gives us a minimum
 *  pixel transfer time of about 2.6ms.  And it's actually very difficult
 *  to achieve that speed - my original, naive implementation took more
 *  like 30ms (!!!) to transfer each frame.
 *  As a rule, I don't like tricky code, because it's hard to understand
 *  and hard to debug.  But in this case it's justified.  For good plunger
 *  tracking, it's critical to achieve a minimum frame rate of around 200 
 *  fps (5ms per frame).  I'm pretty sure there's no way to even get close 
 *  to this rate without the complex setup described below.
 *  Here's our approach for fast data transfer:
 *  First, we put the analog input port (the ADC == Analog-to-Digital 
 *  Converter) in "continuous" mode, at the highest clock speed we can 
 *  program with the available clocks and the fastest read cycle 
 *  available in the ADC hardware.  (The analog input port is the 
 *  GPIO pin attached to the sensor's AO == Analog Output pin, where 
 *  it outputs each pixel's value, one at a time, as an analog voltage 
 *  level.)  In continuous mode, every time the ADC finishes taking a 
 *  sample, it stores the result value in its output register and then 
 *  immediately starts taking a new sample.  This means that no MCU 
 *  (or even DMA) action is required to start each new sample.  This 
 *  is where most of the speedup comes from, since it takes significant
 *  time (multiple microseconds) to move data through the peripheral 
 *  registers, and it takes more time (also multiple microseconds) for
 *  the ADC to spin up for each new sample when in single-sample mode.
 *  We cut out about 7us this way and get the time per sample down to 
 *  about 2us.  This is close to the documented maximum speed for the
 *  ADC hardware.
 *  Second, we use the DMA controller to read the ADC result register
 *  and store each sample in a memory array for processing.  The ADC
 *  hardware is designed to work with the DMA controller by signaling
 *  the DMA controller when a new sample is ready; this allows DMA to
 *  move each sample immediately when it's available without any CPU
 *  involvement.
 *  Third - and this is where it really gets tricky - we use two
 *  additional "linked" DMA channels to generate the clock signal
 *  to the CCD sensor.  The clock signal is how we tell the CCD when
 *  to place the next pixel voltage on its AO pin, so the clock has
 *  to be generated in lock step with the ADC sampling cycle.  The
 *  ADC timing isn't perfectly uniform or predictable, so we can't 
 *  just generate the pixel clock with a *real* clock.  We have to
 *  time the signal exactly with the ADC, which means that we have 
 *  to generate it from the ADC "sample is ready" signal.  Fortunately,
 *  there is just such a signal, and in fact we're already using it,
 *  as described above, to tell the DMA when to move each result from
 *  the ADC output register to our memory array.  So how do we use this
 *  to generate the CCD clock?  The answer lies in the DMA controller's
 *  channel linking feature.  This allows one DMA channel to trigger a
 *  second DMA channel each time the first channel completes one
 *  transfer.  And we can use DMA to control our clock GPIO pin by
 *  using the pin's GPIO IPORT register as the DMA destination address.
 *  Specifically, we can take the clock high by writing our pin's bit 
 *  pattern to the PSOR ("set output") register, and we can take the 
 *  clock low by writing to the PCOR ("clear output") register.  We 
 *  use one DMA channel for each of these operations.
 *  Putting it all together, the cascade of linked DMA channels
 *  works like this:
 *   - We kick off the first ADC sample.
 *   - When the ADC sample completes, the ADC DMA trigger fires,
 *     which triggers channel 1, the "Clock Up" channel.  This 
 *     performs one transfer of the clock GPIO bit to the clock 
 *     PSOR register, taking the clock high, which causes the CCD 
 *     to move the next pixel onto AO.
 *   - After the Clock Up channel does its transfer, it triggers
 *     its link to channel 2, the ADC transfer channel.  This
 *     channel moves the ADC output register value to our memory
 *     array.
 *   - After the ADC channel does its transfer, it triggers channel
 *     3, the "Clock Down" channel.  This performs one transfer of
 *     the clock GPIO bit to the clock PCOR register, taking the
 *     clock low.
 *  Note that the order of the channels - Clock Up, ADC, Clock Down -
 *  is important.  It ensures that we don't toggle the clock line
 *  too quickly.  The CCD has a minimum pulse duration of 50ns for
 *  the clock signal.  The DMA controller is so fast that it might
 *  toggle the clock faster than this limit if we did the Up and 
 *  Down transfers back-to-back.
 *  Note also that it's important for Clock Up to be the very first
 *  operation after the DMA trigger.  The ADC is in continuous mode, 
 *  meaning that it starts taking a new sample immediately upon 
 *  finishing the previous one.  So when the ADC DMA signal fires, 
 *  the new sample is already starting.  We therefore have to get 
 *  the next pixel onto the sampling pin immediately, or as close
 *  to immediately as possible.  The sensor's "analog output 
 *  settling time" is 120ns - this is the time for a new pixel 
 *  voltage to stabilize on AO after a clock rising edge.  So 
 *  assuming that the ADC raises the DMA signal immediately on
 *  sample completion, and the DMA controller responds within a 
 *  couple of MCU clock cycles, we should have the new pixel voltage 
 *  stable on the sampling pin by about 200ns after the new ADC 
 *  sample cycle starts.  The sampling cycle with our current 
 *  parameters is about 2us, so the voltage level is stable for 
 *  90% of the cycle.  
 *  Also, note that it's okay that the ADC sample transfer doesn't
 *  happen until after the Clock Up DMA transfer.  The ADC output 
 *  register holds the last result until the next sample completes, 
 *  so we have about 2us to grab it.  The first Clock Up DMA 
 *  transfer only takes a couple of clocks - order of 100ns - so 
 *  we get to it with time to spare.
 *  (Note that it would nicer to handle the clock with a single DMA
 *  channel, since DMA channels are a limited resource.  We could
 *  conceivably consolidate the clock generator one DMA channel by
 *  switching the DMA destination to the PTOR "toggle" register, and
 *  writing *two* times per trigger - once to toggle the clock up, 
 *  and a second time to toggle it down.  But I haven't found a way 
 *  to make this work.  The obstacle is that the DMA controller can 
 *  only do one transfer per trigger in the fully autonomous mode 
 *  we're using, and to make this toggle scheme work, we'd have to do 
 *  two writes per trigger.  Maybe even three or four:  I think we'd
 *  have to throw in one or two no-op writes (of all zeroes) between 
 *  the two toggles, to pad the timing to ensure that the clock pulse 
 *  width is over the sensor's 50ns minimum.  But it's the same issue 
 *  whether it's two writes or four.  The DMA controller does have a 
 *  "continuous" mode that does an entire transfer on a single trigger,
 *  but it can't reset itself after such a transfer; CPU intervention 
 *  is required to do that, which means we'd have to service an 
 *  interrupt on every ADC cycle to set up the next clock write.  
 *  Given the 2us cycle time, an interrupt would create a ton of CPU 
 *  load, and I don't think the CPU is fast enough to reliably complete
 *  the work we'd have to do on each 2us cycle.  Fortunately, at
 *  the moment we can afford to dedicate three channels to this
 *  module.  We only have one other module using the DMA at all
 *  (the TLC5940 PWM controller interface), and it only needs one
 *  channel.  So the KL25Z's complement of four DMA channels is just
 *  enough for all of our needs for the moment.)
 *  Note that some of the sensors in this series (TSL1410R, TSL1412S)
 *  have a "parallel" readout mode that lets them physically deliver 
 *  two pixels at once the MCU, via separate physical connections.  This 
 *  could provide a 2X speedup on an MCU equipped with two independent 
 *  ADC samplers.  Unfortunately, the KL25Z is not so equipped; even 
 *  though it might appear at first glance to support multiple ADC 
 *  "channels", all of the channels internally multiplex into a single 
 *  converter unit, so the hardware can ultimately perform only one 
 *  conversion at a time.  Paradoxically, using the sensor's parallel 
 *  mode is actually *slower* with a KL25Z than using its serial mode,
 *  because we can only maintain the higher throughput of the KL25Z ADC's
 *  continuous sampling mode by reading all samples thorugh a single
 *  channel.  Switching channels on alternating samples involves a
 *  bunch of setup overhead within the ADC hardware that adds lots of
 *  clocks compared to single-channel continuous mode.
#include "mbed.h"
#include "config.h"
#include "AltAnalogIn.h"
#include "SimpleDMA.h"
#include "DMAChannels.h"
#ifndef TSL14XX_H
#define TSL14XX_H

// To allow DMA access to the clock pin, we need to point the DMA
// controller to the IOPORT registers that control the pin.  PORT_BASE()
// gives us the address of the register group for the 32 GPIO pins with
// the same letter name as our target pin (e.g., PTA0 through PTA31), 
// and PINMASK gives us the bit pattern to write to those registers to
// access our single GPIO pin.  Each register group has three special
// registers that update the pin in particular ways:  PSOR ("set output 
// register") turns pins on, PCOR ("clear output register") turns pins 
// off, and PTOR ("toggle output register") toggle pins to the opposite
// of their current values.  These registers have special semantics:
// writing a bit as 0 has no effect on the corresponding pin, while
// writing a bit as 1 performs the register's action on the pin.  This
// allows a single GPIO pin to be set, cleared, or toggled with a
// 32-bit write to one of these registers, without affecting any of the
// other pins addressed by the register.  (It also allows changing any
// group of pins with a single write, although we don't use that
// feature here.)
// - To turn a pin ON:  PORT_BASE(pin)->PSOR = PINMASK(pin)
// - To turn a pin OFF: PORT_BASE(pin)->PCOR = PINMASK(pin)
// - To toggle a pin:   PORT_BASE(pin)->PTOR = PINMASK(pin)
#define GPIO_PORT(pin)        (((unsigned int)(pin)) >> PORT_SHIFT)
#define GPIO_PORT_BASE(pin)   ((GPIO_Type *)(PTA_BASE + GPIO_PORT(pin) * 0x40))
#define GPIO_PINMASK(pin)     gpio_set(pin)
    extern uint64_t mainLoopIterCheckpt[];
    extern Timer mainLoopTimer;)
class TSL14xx
    // Set up the interface.  
    //  nPixSensor = native number of pixels on sensor
    //  siPin = SI pin (GPIO, digital out)
    //  clockPin = CLK pin (GPIO, digital out)
    //  aoPin = AO pin (GPIO, analog in - must be ADC-capable)
    TSL14xx(int nPixSensor, PinName siPin, PinName clockPin, PinName aoPin)
        : adc_dma(DMAch_TSL_ADC), 
          ao(aoPin, true, 0),  // continuous sampling, fast sampling mode
        // Calibrate the ADC for best accuracy
        // start the sample timer with an arbitrary zero point of 'now'
        // start with no minimum integration time
        tIntMin = 0;
        // allocate our double pixel buffers
        pix1 = new uint8_t[nPixSensor*2];
        pix2 = pix1 + nPixSensor;
        // put the first DMA transfer into the first buffer (pix1)
        pixDMA = 0;
        // DMA owns both buffers until the first transfer completes
        clientOwnsStablePix = true;

        // remember the clock pin port base and pin mask for fast access
        clockPort = GPIO_PORT_BASE(clockPin);
        clockMask = GPIO_PINMASK(clockPin);
        // clear out power-on random data by clocking through all pixels twice
        // Set up the Clock Up DMA channel.  This channel takes the
        // clock high by writing the clock bit to the PSOR (set output) 
        // register for the clock pin.
        clkUp_dma.source(&clockMask, false, 32);
        clkUp_dma.destination(&clockPort->PSOR, false, 32);

        // Set up the Clock Down DMA channel.  This channel takes the
        // clock low by writing the clock bit to the PCOR (clear output)
        // register for the clock pin.
        clkDn_dma.source(&clockMask, false, 32);
        clkDn_dma.destination(&clockPort->PCOR, false, 32);
        // Set up the ADC transfer DMA channel.  This channel transfers
        // the current analog sampling result from the ADC output register
        // to our pixel array.

        // Set up our chain of linked DMA channel:
        //   ADC sample completion triggers Clock Up
        //   ...which triggers the ADC transfer
        //   ...which triggers Clock Down
        // We operate the ADC in "continuous mode", meaning that it starts
        // a new sample immediately after the last one completes.  This is
        // what keeps the cycle going after the Clock Down, since the Clock
        // Down transfer itself doesn't trigger another DMA operation.
        clkUp_dma.trigger(Trigger_ADC0);;, false);
        // Set the trigger on the downstream links to NONE - these are
        // triggered by their upstream links, so they don't need separate
        // peripheral or software triggers.
        // Register an interrupt callback so that we're notified when
        // the last transfer completes.
        clkDn_dma.attach(this, &TSL14xx::transferDone);

        // clear the timing statistics        
        totalTime = 0.0; 
        nRuns = 0;
        // start the first transfer
    // Get the stable pixel array.  This is the image array from the
    // previous capture.  It remains valid until the next startCapture()
    // call, at which point this buffer will be reused for the new capture.
    void getPix(uint8_t * &pix, uint32_t &t)
        // return the pixel array that ISN'T assigned to the DMA
        if (pixDMA)
            // DMA owns pix2, so the stable array is pix1
            pix = pix1;
            t = t1;
            // DMA owns pix1, so the stable array is pix2
            pix = pix2;
            t = t2;
    // Wait for the current DMA transfer to finish, and retrieve its
    // pixel array buffer.  This provides access to the latest image
    // without starting a new transfer.  These pixels are valid throughout
    // the next transfer (started via startCapture()) and remain valid 
    // until the next transfer after that.
    void waitPix(uint8_t * &pix, uint32_t &t)
        // wait for stable buffer ownership to transfer to the client
        // Return the pixel array that IS assigned to DMA, since this
        // is the latest buffer filled.  This buffer is stable, even
        // though it's assigned to DMA, because the last transfer is
        // already finished and thus DMA is no longer accessing the
        // buffer.
        if (pixDMA)
            // DMA owns pix2
            pix = pix2;
            t = t2;
            // DMA owns pix1
            pix = pix1;
            t = t1;
    // Set the requested minimum integration time.  If this is less than the
    // sensor's physical minimum time, the physical minimum applies.
    virtual void setMinIntTime(uint32_t us)
        tIntMin = us;
    // Wait for the stable buffer ownership to transfer to the client
    void wait() { while (!clientOwnsStablePix) ; }
    // Is a buffer available?
    bool ready() const { return clientOwnsStablePix; }
    // Release the client DMA buffer.  The client must call this when it's
    // done with the current image frame to release the frame back to the
    // DMA subsystem, so that it can hand us the next frame.
    void releasePix() { clientOwnsStablePix = false; }
    // get the timing statistics - sum of scan time for all scans so far 
    // in microseconds, and total number of scans so far
    void getTimingStats(uint64_t &totalTime, uint32_t &nRuns) const
        totalTime = this->totalTime;
        nRuns = this->nRuns;
    // get the average scan time in microseconds
    uint32_t getAvgScanTime() const
        return uint32_t(totalTime / nRuns);
    // Start a new transfer.  We call this at the end of each integration
    // cycle, in interrupt mode.  This can be called directly by the interrupt
    // handler invoked when the DMA transfer completes, or by a timeout.  In
    // either case, we're in interrupt mode.
    void startTransfer()
        // If we own the stable buffer, swap buffers: hand ownership of the
        // old DMA buffer to the client, and take control of the old client
        // buffer (which the client must be done with if we own it) as our
        // new DMA buffer.
        // If the client owns the stable buffer, we can't swap buffers,
        // because the client is still working on the stable one.  So we
        // must start the new transfer using the existing DMA buffer.
        if (!clientOwnsStablePix)
            // swap buffers
            pixDMA ^= 1;
            // release the prior DMA buffer to the client
            clientOwnsStablePix = true;
        // Set up the active pixel array as the destination buffer for 
        // the ADC DMA channel. 
        adc_dma.destination(pixDMA ? pix2 : pix1, true);

        // start the DMA transfers
        clkDn_dma.start(nPixSensor*4, true);
        adc_dma.start(nPixSensor, true);
        clkUp_dma.start(nPixSensor*4, true);
        // note the start time of this transfer
        t0 = t.read_us();
        // start the next integration cycle by pulsing SI and one clock
        si = 1;
        clock = 1;
        si = 0;
        clock = 0;
        // Set the timestamp for the current active buffer.  The SI pulse
        // we just did performed the HOLD operation, which takes a snapshot
        // of the photo receptors and stores it in the sensor's shift
        // register.  We noted the start of the current integration cycle 
        // in tInt when we started it during the previous scan.  The image 
        // we're about to transfer therefore represents the light collected
        // between tInt and right now (actually, the SI pulse above, but 
        // close enough).  The image covers a time range rather than a
        // single point in time, but we still have to give it a single
        // timestamp.  Use the midpoint of the integration period.
        uint32_t tmid = (t0 + tInt) >> 1;
        if (pixDMA)
            t2 = tmid;
            t1 = tmid;

        // Start the ADC sampler.  The ADC will read samples continuously
        // until we tell it to stop.  Each sample completion will trigger 
        // our linked DMA channel, which will store the next sample in our
        // pixel array and pulse the CCD serial data clock to load the next
        // pixel onto the analog sampler pin.  This will all happen without
        // any CPU involvement, so we can continue with other work.
        // The new integration cycle starts with the 19th clock pulse
        // after the SI pulse.  We offload all of the transfer work (including
        // the clock pulse generation) to the DMA controller, which doesn't
        // notify when that 19th pulse occurs, so we have to approximate.
        // Based on empirical measurements, each pixel transfer in our DMA
        // setup takes about 2us, so clocking 19 pixels takes about 38us.
        // In addition, the ADC takes about 4us extra for the first read.
        tInt = t.read_us() + 19*2 + 4;
    // End of transfer notification.  This is called as an interrupt
    // handler when the DMA transfer completes.
    void transferDone()
        // stop the ADC sampler
        // clock out one extra pixel to leave the analog out pin on
        // the sensor in the high-Z state
        clock = 1;
        clock = 0;
        // add this sample to the timing statistics (for diagnostics and
        // performance measurement)
        uint32_t now = t.read_us();
        totalTime += uint32_t(now - t0);
        nRuns += 1;
        // note the ending time of the transfer
        tDone = now;
        // Figure the time remaining to reach the minimum requested 
        // integration time for the next cycle.  The sensor is currently
        // working on an integration cycle that started at tInt, and that
        // cycle will end when we start the next cycle.  We therefore want
        // to wait to start the next cycle until we've reached the desired
        // total integration time.
        uint32_t dt = now - tInt;
        // Figure the time to the start of the next transfer.  Wait for the
        // remainder of the current integration period if we haven't yet
        // reached the requested minimum, otherwise just start almost
        // immediately.  (Not *actually* immediately: we don't want to start 
        // the new transfer within this interrupt handler, because the DMA
        // IRQ doesn't reliably clear if we start a new transfer immediately.)
        uint32_t dtNext = dt < tIntMin ? tIntMin - dt : 1;

        // Schedule the next transfer
        integrationTimeout.attach_us(this, &TSL14xx::startTransfer, dtNext);

    // Clear the sensor shift register.  Clocks in all of the pixels from
    // the sensor without bothering to read them on the ADC.  Pulses SI 
    // at the beginning of the operation, which starts a new integration 
    // cycle.
    void clear()
        // get the clock toggle register
        volatile uint32_t *ptor = &clockPort->PTOR;
        // make sure any DMA run is completed
        // clock in an SI pulse
        si = 1;
        *ptor = clockMask;
        clockPort->PSOR = clockMask;
        si = 0;
        *ptor = clockMask;
        // This starts a new integration period.  Or more precisely, the
        // 19th clock pulse will start the new integration period.  We're
        // going to blast the clock signal as fast as we can, at about
        // 100ns intervals (50ns up and 50ns down), so the 19th clock
        // will be about 2us from now.
        tInt = t.read_us() + 2;
        // clock out all pixels, plus an extra one to clock past the last
        // pixel and reset the last pixel's internal sampling switch in
        // the sensor
        for (int i = 0 ; i < nPixSensor + 1 ; ) 
            // toggle the clock to take it high
            *ptor = clockMask;
            // increment our loop variable here to pad the timing, to
            // keep our pulse width long enough for the sensor
            // toggle the clock to take it low
            *ptor = clockMask;
    // DMA controller interfaces
    SimpleDMA adc_dma;        // DMA channel for reading the analog input
    SimpleDMA clkUp_dma;      // "Clock Up" channel
    SimpleDMA clkDn_dma;      // "Clock Down" channel

    // Sensor interface pins
    DigitalOut si;            // GPIO pin for sensor SI (serial data) 
    DigitalOut clock;         // GPIO pin for sensor SCLK (serial clock)
    GPIO_Type *clockPort;     // IOPORT base address for clock pin - cached for DMA writes
    uint32_t clockMask;       // IOPORT register bit mask for clock pin
    AltAnalogIn_8bit ao;           // GPIO pin for sensor AO (analog output)
    // number of pixels in the physical sensor array
    int nPixSensor;           // number of pixels in physical sensor array

    // pixel buffers - we keep two buffers so that we can transfer the
    // current sensor data into one buffer via DMA while we concurrently
    // process the last buffer
    uint8_t *pix1;            // pixel array 1
    uint8_t *pix2;            // pixel array 2
    // Timestamps of pix1 and pix2 arrays, in microseconds, in terms of the 
    // sample timer (this->t).
    uint32_t t1;
    uint32_t t2;
    // DMA target buffer.  This is the buffer for the next DMA transfer.
    // 0 means pix1, 1 means pix2.  The other buffer contains the stable 
    // data from the last transfer.
    uint8_t pixDMA;
    // Stable buffer ownership.  At any given time, the DMA subsystem owns
    // the buffer specified by pixDMA.  The other buffer - the "stable" buffer,
    // which contains the most recent completed frame, can be owned by EITHER
    // the client or by the DMA subsystem.  Each time a DMA transfer completes,
    // the DMA subsystem looks at the stable buffer owner flag to determine 
    // what to do:
    // - If the DMA subsystem owns the stable buffer, it swaps buffers.  This
    //   makes the newly completed DMA buffer the new stable buffer, and makes
    //   the old stable buffer the new DMA buffer.  At this time, the DMA 
    //   subsystem also changes the stable buffer ownership to CLIENT.
    // - If the CLIENT owns the stable buffer, the DMA subsystem can't swap
    //   buffers, because the client is still using the stable buffer.  It
    //   simply leaves things as they are.
    // In either case, the DMA system starts a new transfer at this point.
    // The client, meanwhile, is free to access the stable buffer when it has
    // ownership.  If the client *doesn't* have ownership, it must wait for
    // the ownership to be transferred, which can only be done by the DMA
    // subsystem on completing a transfer.
    // When the client is done with the stable buffer, it transfers ownership
    // back to the DMA subsystem.
    // Transfers of ownership from DMA to CLIENT are done only by DMA.
    // Transfers from CLIENT to DMA are done only by CLIENT.  So whoever has
    // ownership now is responsible for transferring ownership.
    volatile bool clientOwnsStablePix;
    // End-of-integration timeout handler.  This lets us fire an interrupt
    // when the current integration cycle is done, so that we can start the
    // next cycle.
    Timeout integrationTimeout;
    // Requested minimum integration time, in micoseconds.  The client can use 
    // this to control the exposure level, by increasing it for a longer
    // exposure and thus more light-gathering in low-light conditions.  Note 
    // that the physical limit on the minimum integration time is roughly equal 
    // to the pixel file transfer time, because the integration cycle is
    // initiated and ended by transfer starts.  It's thus impossible to make
    // the integration time less than the time for one full pixel file 
    // transfer.
    uint32_t tIntMin;
    // timing statistics
    Timer t;                  // sample timer
    uint32_t t0;              // start time (us) of current sample
    uint32_t tInt;            // start time (us) of current integration period
    uint32_t tDone;           // end time of latest finished transfer
    uint64_t totalTime;       // total time consumed by all reads so far
    uint32_t nRuns;           // number of runs so far
#endif /* TSL14XX_H */