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.)

Files at this revision

API Documentation at this revision

Sat Apr 18 19:08:55 2020 +0000
Commit message:
TCD1103 DMA setup time padding to fix sporadic missed first pixel in transfer; fix TV ON so that the TV ON IR commands don't have to be grouped in the IR command first slots

Changed in this revision

NewPwm/NewPwm.h Show annotated file Show diff for this revision Revisions of this file
Plunger/plunger.h Show annotated file Show diff for this revision Revisions of this file
Plunger/tcd1103Sensor.h Show annotated file Show diff for this revision Revisions of this file
TCD1103/TCD1103.h Show annotated file Show diff for this revision Revisions of this file
main.cpp Show annotated file Show diff for this revision Revisions of this file
diff -r bd5d4bd4383b -r 310ac82cbbee NewPwm/NewPwm.h
--- a/NewPwm/NewPwm.h	Tue Feb 18 21:33:30 2020 +0000
+++ b/NewPwm/NewPwm.h	Sat Apr 18 19:08:55 2020 +0000
@@ -244,7 +244,7 @@
     // wait for the end of the current cycle
-    void waitEndCycle()
+    inline void waitEndCycle()
         // clear the overflow flag (note the usual KL25Z convention for 
         // hardware status registers like this: writing '1' clears the bit)
@@ -282,8 +282,8 @@
     // be OFF 10% of the time and ON 90% of the time.  This is primarily
     // for complex timing situations where the caller has to be able to
     // coordinate the alignment of up/down transitions on the output; in
-    // particularly, it allows the caller to use the waitEndCycle() to sync
-    // with the falling ege on the output.
+    // particular, it allows the caller to use the waitEndCycle() to sync
+    // with the falling edge on the output.
     NewPwmOut(PinName pin, bool invertedCycle = false)
         // determine the TPM unit number and channel
diff -r bd5d4bd4383b -r 310ac82cbbee Plunger/plunger.h
--- a/Plunger/plunger.h	Tue Feb 18 21:33:30 2020 +0000
+++ b/Plunger/plunger.h	Sat Apr 18 19:08:55 2020 +0000
@@ -538,53 +538,47 @@
                 // There's a shortcut we can use here to make this loop go a
                 // lot faster than the naive approach.  Note that 255 decimal
-                // is 1111111 binary.  Subtracting any other binary number
-                // (in the range 0..255) from 255 will have the effect of 
-                // simply inverting all of the bits in the original number.  
-                // So 255 - X == ~X for any X in 0..255.  That might not sound
-                // like a big deal, but it's actually pretty great, because it
-                // means that we only have to operate on the bits individually,
-                // rather than doing arithmetic on the bytes.  And if we can
-                // operate on the bits individually, we can operate on them
-                // in the largest groups we can with the processor's native
-                // instruction set, which in the case of ARM is 32-bit DWORDs.
-                // In other words, we can iterate over the array as a DWORD
-                // array rather than a BYTE array, which cuts loop iterations
-                // by a factor of 4.
+                // is 1111111 binary.  Subtracting any number in (0..255) from
+                // 255 is the same as inverting the bits in the other number.
+                // That is, 255 - X == ~X for all X in 0..255.  That's useful
+                // because it means that we can compute (255-X) as a purely
+                // bitwise operation, which means that we can perform it on
+                // blocks of bytes instead of individual bytes.  On ARM, we
+                // can perform bitwise operations four bytes at a time via
+                // DWORD instructions.  This lets us compute (255-X) for N
+                // bytes using N/4 loop iterations.
                 // One other small optimization we can apply is to notice that
-                // ~X == X ^ ~0, and X ^= ~0 happens to optimize to a single
-                // ARM instruction.  So we can make the ARM C++ compiler 
-                // translate this loop into three assembly instructions (XOR
-                // with immediate data and auto-increment pointer, decrement
-                // counter, jump if not zero), which is as fast as we could
-                // write it in assembly by hand.  (This really works in
-                // practice, too: I clocked this loop at 60us for the 
-                // 1500-pixel TCD1103 array.)
+                // ~X == X ^ ~0, and that X ^= ~0 can be performed with a
+                // single ARM instruction.  So we can make the ARM C++ compiler
+                // translate the loop body into just three instructions:  XOR 
+                // with immediate data and auto-increment pointer, decrement 
+                // the counter, and jump if not zero.  That's as fast we could
+                // do it in hand-written assembly.  I clocked this loop at 
+                // 60us for the 1536-pixel TCD1103 array.
+                //
+                // Note two important constraints:
+                //
+                //  - 'pix' must be aligned on a DWORD (4-byte) boundary.
+                //    This is REQUIRED, because the XOR in the loop uses a
+                //    DWORD memory operand, which will halt the MCU with a
+                //    bus error if the pointer isn't DWORD-aligned.
+                //
+                //  - 'n' must be a multiple of 4 bytes.  This isn't strictly
+                //    required, but if it's not observed, the last (N - N/4)
+                //    bytes won't be inverted.
+                //
+                // The only sensor that uses a negative image is the TCD1103.
+                // Its buffer is DWORD-aligned because it's allocated via
+                // malloc(), which always does worst-case alignment.  Its
+                // buffer is 1546 bytes long, which violates the multiple-of-4
+                // rule, but inconsequentially, as the last 14 bytes represent
+                // dummy pixels that can be ignored (so it's okay that we'll 
+                // miss inverting the last two bytes).
                 uint32_t *pix32 = reinterpret_cast<uint32_t*>(pix);
                 for (int i = n/4; i != 0; --i)
                     *pix32++ ^= 0xFFFFFFFF;
-                // Note!  If we ever needed to do this with a sensor where
-                // the pixel count isn't a multiple of four, we'd have to
-                // add some code here to deal with the stragglers (the one,
-                // two, or three extra pixels after the last group of four).
-                // That's not an issue with any currently supported sensor,
-                // nor is it likely to be in the future (because any large
-                // pixel array will be built out of repeated submodules, 
-                // which inherently makes power-of-two bases likely, and
-                // because engineers tend to have a bias for round numbers
-                // even when they have to choose arbitrarily).  So I'm not
-                // going to test for this possibility, to save the run-time
-                // cost.  And the worst that happens is we see a couple of
-                // glitchy-looking pixels at the end of the array in the 
-                // visualizer on the client.  But just in case, here's the
-                // code that would be needed...
-                //
-                // int extraPix = n & 3;  // remainder of n/4
-                // for (int i = 0; i < extraPix; ++i)
-                //     reinterpret_cast<uint8_t*>(pix32)[i] ^= 0xFF;
             // send the pixels in report-sized chunks until we get them all
diff -r bd5d4bd4383b -r 310ac82cbbee Plunger/tcd1103Sensor.h
--- a/Plunger/tcd1103Sensor.h	Tue Feb 18 21:33:30 2020 +0000
+++ b/Plunger/tcd1103Sensor.h	Sat Apr 18 19:08:55 2020 +0000
@@ -58,7 +58,7 @@
     PlungerSensorImageInterfaceTCD1103(PinName fm, PinName os, PinName icg, PinName sh)
-        : PlungerSensorImageInterface(1500), sensor(fm, os, icg, sh)
+        : PlungerSensorImageInterface(1546), sensor(fm, os, icg, sh)
@@ -89,7 +89,7 @@
     PlungerSensorTCD1103(PinName fm, PinName os, PinName icg, PinName sh)
-        : PlungerSensorImage(sensor, 1500, 1499, true), sensor(fm, os, icg, sh)
+        : PlungerSensorImage(sensor, 1546, 1545, true), sensor(fm, os, icg, sh)
@@ -102,11 +102,41 @@
     // we see starting at the "far" end.
     virtual bool process(const uint8_t *pix, int n, int &pos, int& /*processResult*/)
+        // The TCD1103's pixel file that it reports on the wire has the 
+        // following internal structure:
+        //
+        //   16 dummy elements, fixed at the dark charge level
+        //   13 light-shielded pixels (live pixels, covered with a shade in the sensor)
+        //   3 dummy "buffer" pixels (to allow for variation in shade alignment)
+        //   1500 image pixels
+        //   14 dummy elements (the data sheet doesn't say exactly what these are physically)
+        //
+        // The sensor holds the 16 dummy elements at the dark charge level,
+        // so they provide a reference point for the darkest reading possible.
+        // The light-shielded pixels serve essentially the same purpose, in
+        // that they *also* should read out at the dark charge level.  But
+        // the shaded pixels can be also used for diagnostics, to distinguish
+        // between problems in the CCD proper and problems in the interface
+        // electronics.  If the dummy elements are reading at the dark level
+        // but the shielded pixels aren't, you have a CCD problem; if the
+        // dummy pixels aren't reading at the dark level, the interface
+        // electronics are suspect.
+        //
+        // For our purposes, we can simply ignore the dummy pixels at either
+        // end.  The diagnostic status report for the Config Tool sends the
+        // full view including the dummy pixels, so any diagnostics that the
+        // user wants to do using the dummy pixels can be done on the PC side.
+        //
+        // Deduct the dummy pixels so that we only scan the true image
+        // pixels in our search for the plunger edge.
+        int startOfs = 32;
+        n -= 32 + 14;
         // Scan the pixel array to determine the actual dynamic range 
         // of this image.  That will let us determine what consistutes
         // "bright" when we're looking for the bright spot.
         uint8_t pixMin = 255, pixMax = 0;
-        const uint8_t *p = pix;
+        const uint8_t *p = pix + startOfs;
         for (int i = n; i != 0; --i)
             uint8_t c = *p++;
@@ -120,7 +150,7 @@
         // Scan for the first bright-enough pixel.  Remember that we're
         // working with a negative image, so "brighter" is "less than".
-        p = pix;
+        p = pix + startOfs;
         for (int i = n; i != 0; --i, ++p)
             if (*p < threshold)
diff -r bd5d4bd4383b -r 310ac82cbbee TCD1103/TCD1103.h
--- a/TCD1103/TCD1103.h	Tue Feb 18 21:33:30 2020 +0000
+++ b/TCD1103/TCD1103.h	Sat Apr 18 19:08:55 2020 +0000
@@ -159,16 +159,18 @@
         // ADC sample conversion time.  This must be calculated based on the
         // combination of parameters selected for the os() initializer above.
-        // See the KL25 Sub-Family Reference Manual, section 28.4.45, for the
-        // formula.
-        const float ADC_TIME = 2.2083333e-6f; // 6-cycle long sampling, no averaging
+        // See the KL25 Sub-Family Reference Manual, section, for the
+        // formula.  We operate in single-sample mode, so when you read the
+        // Reference Manual tables, the sample time value to use is the
+        // "First or Single" value.
+        const float ADC_TIME = 2.1041667e-6f; // 6-cycle long sampling, no averaging
         // Set the TPM cycle time to satisfy our timing constraints:
         //   Tm + epsilon1 < A < 2*Tm - epsilon2
         // where A is the ADC conversion time and Tm is the master clock
-        // period, and the epsilons are a margin of safety for any 
+        // period, and the epsilons provide a margin of safety for any 
         // non-deterministic component to the timing of A and Tm.  The
         // epsilons could be zero if the timing of the ADC is perfectly
         // deterministic; this must be determined empirically.
@@ -185,7 +187,7 @@
         // fast plunger motion accurately.  Empirically, we can get reliable
         // results by using half of the ADC time plus a small buffer time.
-        fm.getUnit()->period(masterClockPeriod = ADC_TIME/2 + 0.1e-6f);
+        fm.getUnit()->period(masterClockPeriod = ADC_TIME/2 + 0.25e-6f);
         // Start the master clock running with a 50% duty cycle
@@ -249,12 +251,6 @@
             pix = pix2;
             t = t2;
-        // The raw pixel array we transfer in from the sensor on the serial 
-        // connection consists of 32 dummy elements, followed by 1500 actual
-        // image pixels, followed by 14 dummy elements.  Skip the leading 32 
-        // dummy pixels when passing the buffer back to the client.
-        pix += 32;
     // release the client's pixel buffer
@@ -370,6 +366,9 @@
     uint32_t gen_SH_ICG_pulse(bool start_dma_xfer)
+        // Make sure the ADC is stopped
+        os.stop();
         // If desired, prepare to start the DMA transfer for the ADC data.
         // (Set up a dummy location to write in lieu of the DMA register if
         // DMA initiation isn't required, so that we don't have to take the
@@ -436,9 +435,9 @@
         // with the start of an ADC cycle.  If we get that wrong, all of our
         // ADC samples will be off by half a clock, so every sample will be
         // the average of two adjacent pixels instead of one pixel.  That
-        // would lose half of the image resolution, which would obviously
-        // be bad.  So make certain we're at the tail end of an ADC cycle
-        // by waiting for the ADC "ready" bit to be set.
+        // would have the effect of shifting the image by half a pixel,
+        // which could make our edge detection jitter by one pixel from one
+        // frame to the next.  So we definitely want to avoid this.
         // The end of the SH pulse triggers the start of a new integration 
         // cycle, so note the time of that pulse for image timestamping 
@@ -447,15 +446,12 @@
         // represent the pixels from the last time we pulsed SH.
         icg = logicLow;
-        icg = logicLow;  // for timing, adds about 60ns
-        icg = logicLow;  // ditto, another 60ns, total is now 120ns > min 100ns
-        icg = logicLow;  // one more to be safer
+        icg = logicLow;  // for timing, adds about 150ns > min 100ns
         sh = logicHigh;  // take SH high
         wait_us(1);      // >1000ns delay
         sh = logicHigh;  // a little more padding to be sure we're over the minimum
-        sh = logicHigh;  // more padding
         sh = logicLow;   // take SH low
@@ -514,9 +510,6 @@
         //   - End the ICG pulse
-        // disable the TPM->ADC trigger and abort the current conversion
-        os.stop();
         // Enable the DMA controller for the new transfer from the ADC.
         // The sensor will start clocking out new samples at the ICG rising
         // edge, so the next ADC sample to complete will represent the first
@@ -530,10 +523,24 @@
         // wait for the start of a new master clock cycle
+        // Wait one more cycle to be sure the DMA is ready.  Empirically,
+        // this extra wait is actually required; evidently DMA startup has
+        // some non-deterministic timing element or perhaps an asynchronous
+        // external dependency.  In any case, *without* this extra wait,
+        // the DMA transfer sporadically (about 20% probability) misses the
+        // very first pixel that the sensor clocks out, so the entire image
+        // is shifted "left" by one pixel.  That makes the position sensing
+        // jitter by a pixel from one frame to the next according to whether
+        // or not we had that one-pixel delay in the DMA startup.  Happily,
+        // padding the timing by an fM cycle seems to make the DMA startup
+        // perfectly reliable.
+        fm.waitEndCycle();
         // Okay, a master clock cycle just started, so we have about 1us 
         // (about 16 CPU instructions) before the next one begins.  Resume 
         // ADC sampling.  The first new sample will start with the next
-        // TPM cycle 1us from now.  (This step takes about 3 instructions.)
+        // TPM cycle 1us from now.  This step itself takes about 3 machine
+        // instructions for 180ns, so we have about 820ns left to go.
         // Eerything is queued up!  We just have to fire the starting gun
diff -r bd5d4bd4383b -r 310ac82cbbee main.cpp
--- a/main.cpp	Tue Feb 18 21:33:30 2020 +0000
+++ b/main.cpp	Sat Apr 18 19:08:55 2020 +0000
@@ -4780,8 +4780,11 @@
                 if ((cfg.IRCommand[i].flags & IRFlagTVON) != 0)
                     // It's a TV ON command - check if it's the one we're
-                    // looking for.
-                    if (n == tvon_ir_state)
+                    // looking for.  We can match any code starting at the
+                    // current state.  (We ignore codes BEFORE the current
+                    // state, because we've already processed them on past
+                    // iterations.)
+                    if (n >= tvon_ir_state)
                         // It's the one.  Start transmitting it by
                         // pushing its virtual button.