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

/media/uploads/mjr/pinscape_no_background_small_L7Miwr6.jpg

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 mechanical plunger, button inputs, and feedback device control.

In case you haven't heard of the idea 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 show the backglass artwork. Some cabs also include a third monitor to simulate the DMD (Dot Matrix Display) used for scoring on 1990s machines, or even an original plasma DMD. A computer (usually a Windows PC) 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 trim hardware.

It's possible to buy a pre-built virtual pinball machine, but it also makes a great 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.

Downloads

  • 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.

Documentation

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 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.)

Committer:
mjr
Date:
Fri Dec 27 20:14:23 2019 +0000
Revision:
104:6e06e0f4b476
Parent:
100:1ff35c07217c
AEAT-6012, TCD1103 updates

Who changed what in which revision?

UserRevisionLine numberNew contents of line
mjr 17:ab3cec0c8bf4 1 // Potentiometer plunger sensor
mjr 17:ab3cec0c8bf4 2 //
mjr 17:ab3cec0c8bf4 3 // This file implements our generic plunger sensor interface for a
mjr 43:7a6364d82a41 4 // potentiometer. The potentiometer resistance must be linear in
mjr 43:7a6364d82a41 5 // position. To connect physically, wire the fixed ends of the
mjr 43:7a6364d82a41 6 // potentiometer to +3.3V and GND (respectively), and connect the
mjr 43:7a6364d82a41 7 // wiper to an ADC-capable GPIO pin on the KL25Z. The wiper voltage
mjr 43:7a6364d82a41 8 // that we read on the ADC will vary linearly with the wiper position.
mjr 43:7a6364d82a41 9 // Mechanically attach the wiper to the plunger so that the wiper moves
mjr 43:7a6364d82a41 10 // in lock step with the plunger.
mjr 43:7a6364d82a41 11 //
mjr 100:1ff35c07217c 12 // In practice, the ADC readings from a potentiometer can be noisy,
mjr 100:1ff35c07217c 13 // varying by around 1% from reading to reading when the slider is
mjr 100:1ff35c07217c 14 // stationary. One way to improve this is to use longer sampling times
mjr 100:1ff35c07217c 15 // in the ADC to improve the accuracy of the sampling. We can tolerate
mjr 100:1ff35c07217c 16 // quite long ADC sampling times because even the slow modes are quite
mjr 100:1ff35c07217c 17 // a lot faster than the result rate we require. Another way to reduce
mjr 100:1ff35c07217c 18 // noise is to apply some low-pass filtering. The simplest low-pass
mjr 100:1ff35c07217c 19 // filter is to average a number of samples together. Since our ADC
mjr 100:1ff35c07217c 20 // sampling rate (even with long conversions) is quite a lot faster than
mjr 100:1ff35c07217c 21 // the needed output rate, we can simply average samples over the time
mjr 100:1ff35c07217c 22 // scale where we need discrete outputs.
mjr 100:1ff35c07217c 23 //
mjr 100:1ff35c07217c 24 // Note: even though this class is specifically for potentiometers, it
mjr 100:1ff35c07217c 25 // could also be used with any other type of sensor that represents its
mjr 100:1ff35c07217c 26 // position reading as a single analog voltage level that varies linearly
mjr 104:6e06e0f4b476 27 // with the position, such as an LVDT. Note that linearity is key here:
mjr 104:6e06e0f4b476 28 // this code wouldn't work well with a sensor that produces an analog
mjr 104:6e06e0f4b476 29 // voltage but has a NON-linear response curve with respect to measured
mjr 104:6e06e0f4b476 30 // position. For example, this code wouldn't work well with the old
mjr 104:6e06e0f4b476 31 // Sharp reflective IR proximity/distance sensors, since those have
mjr 104:6e06e0f4b476 32 // power-law response curves. To work with a non-linear sensor, you'd
mjr 104:6e06e0f4b476 33 // have to subclass this class, override readRaw(), and add processing
mjr 104:6e06e0f4b476 34 // that translates the non-linear sensor reading to a linear position
mjr 104:6e06e0f4b476 35 // measurement. Such processing is obviously a function of the physics
mjr 104:6e06e0f4b476 36 // of the particular sensor, so it would have to be crafted for each
mjr 104:6e06e0f4b476 37 // such sensor type.
mjr 100:1ff35c07217c 38 //
mjr 17:ab3cec0c8bf4 39
mjr 100:1ff35c07217c 40 #include "plunger.h"
mjr 100:1ff35c07217c 41 #include "AltAnalogIn.h"
mjr 17:ab3cec0c8bf4 42
mjr 35:e959ffba78fd 43 class PlungerSensorPot: public PlungerSensor
mjr 17:ab3cec0c8bf4 44 {
mjr 17:ab3cec0c8bf4 45 public:
mjr 86:e30a1f60f783 46 // Our native readings are taken as 16-bit ADC samples, so
mjr 86:e30a1f60f783 47 // our native scale is an unsigned 16-bit int, 0..65535.
mjr 100:1ff35c07217c 48 //
mjr 100:1ff35c07217c 49 // Initialize the ADC to take continuous samples, interrupting us
mjr 100:1ff35c07217c 50 // when each conversion finishes so that we can collect the result
mjr 100:1ff35c07217c 51 // in an ISR. For the sampling mode, use long conversions with
mjr 100:1ff35c07217c 52 // 24 ADCK cycles and 8x averaging; this gives us conversion times
mjr 100:1ff35c07217c 53 // of about 37.33us.
mjr 100:1ff35c07217c 54 //
mjr 100:1ff35c07217c 55 PlungerSensorPot(PinName ao) :
mjr 100:1ff35c07217c 56 PlungerSensor(65535),
mjr 100:1ff35c07217c 57 pot(ao, true, 24, 8) // continuous, 24-cycle long samples, 8x averaging -> 37.33us/sample
mjr 17:ab3cec0c8bf4 58 {
mjr 100:1ff35c07217c 59 // calibrate the ADC for best accuracy
mjr 100:1ff35c07217c 60 pot.calibrate();
mjr 100:1ff35c07217c 61
mjr 100:1ff35c07217c 62 // clear the timing statistics
mjr 100:1ff35c07217c 63 totalConversionTime = 0;
mjr 100:1ff35c07217c 64 nSamples = 0;
mjr 100:1ff35c07217c 65
mjr 100:1ff35c07217c 66 // start with everything zeroed
mjr 100:1ff35c07217c 67 history_write_idx = 0;
mjr 100:1ff35c07217c 68 running_sum = 0;
mjr 100:1ff35c07217c 69 for (int i = 0 ; i < countof(history); ++i)
mjr 100:1ff35c07217c 70 history[i] = 0;
mjr 100:1ff35c07217c 71
mjr 100:1ff35c07217c 72 // set the initial timestamp to the arbitrary epoch on the timer
mjr 100:1ff35c07217c 73 current_timestamp = 0;
mjr 100:1ff35c07217c 74
mjr 100:1ff35c07217c 75 // Set up an interrupt handler to collect the ADC results. The
mjr 100:1ff35c07217c 76 // ADC will trigger the interrupt on each completed sample.
mjr 100:1ff35c07217c 77 isrThis = this;
mjr 100:1ff35c07217c 78 NVIC_SetVector(ADC0_IRQn, (uint32_t)&irq_handler_static);
mjr 100:1ff35c07217c 79 NVIC_EnableIRQ(ADC0_IRQn);
mjr 100:1ff35c07217c 80 pot.enableInterrupts();
mjr 100:1ff35c07217c 81
mjr 100:1ff35c07217c 82 // Start the first asynchronous ADC sample. The ADC will run
mjr 100:1ff35c07217c 83 // continuously once started, and we'll collect samples in the ISR.
mjr 100:1ff35c07217c 84 pot.start();
mjr 48:058ace2aed1d 85 timer.start();
mjr 17:ab3cec0c8bf4 86 }
mjr 17:ab3cec0c8bf4 87
mjr 35:e959ffba78fd 88 virtual void init()
mjr 17:ab3cec0c8bf4 89 {
mjr 17:ab3cec0c8bf4 90 }
mjr 17:ab3cec0c8bf4 91
mjr 100:1ff35c07217c 92 // samples are always ready
mjr 100:1ff35c07217c 93 virtual bool ready() { return true; }
mjr 100:1ff35c07217c 94
mjr 48:058ace2aed1d 95 // read the sensor
mjr 86:e30a1f60f783 96 virtual bool readRaw(PlungerReading &r)
mjr 17:ab3cec0c8bf4 97 {
mjr 100:1ff35c07217c 98 // read the current sample components atomically
mjr 100:1ff35c07217c 99 __disable_irq();
mjr 48:058ace2aed1d 100
mjr 100:1ff35c07217c 101 // figure the current average reading over the history window
mjr 100:1ff35c07217c 102 r.pos = running_sum / countof(history);
mjr 100:1ff35c07217c 103 r.t = current_timestamp;
mjr 48:058ace2aed1d 104
mjr 100:1ff35c07217c 105 // done with the atomic read
mjr 100:1ff35c07217c 106 __enable_irq();
mjr 52:8298b2a73eb2 107
mjr 100:1ff35c07217c 108 // we always have a result available
mjr 17:ab3cec0c8bf4 109 return true;
mjr 17:ab3cec0c8bf4 110 }
mjr 52:8298b2a73eb2 111
mjr 100:1ff35c07217c 112 // Figure the average scan time in microseconds
mjr 53:9b2611964afc 113 virtual uint32_t getAvgScanTime()
mjr 53:9b2611964afc 114 {
mjr 100:1ff35c07217c 115 // The effective time per sample is the raw sampling interval
mjr 100:1ff35c07217c 116 // times the averaging window size.
mjr 100:1ff35c07217c 117 if (nSamples == 0)
mjr 100:1ff35c07217c 118 return 0;
mjr 100:1ff35c07217c 119 else
mjr 100:1ff35c07217c 120 return static_cast<uint32_t>(totalConversionTime/nSamples) * countof(history);
mjr 53:9b2611964afc 121 }
mjr 23:14f8c5004cd0 122
mjr 17:ab3cec0c8bf4 123 private:
mjr 48:058ace2aed1d 124 // analog input for the pot wiper
mjr 100:1ff35c07217c 125 AltAnalogIn_16bit pot;
mjr 48:058ace2aed1d 126
mjr 48:058ace2aed1d 127 // timer for input timestamps
mjr 48:058ace2aed1d 128 Timer timer;
mjr 52:8298b2a73eb2 129
mjr 100:1ff35c07217c 130 // total sampling time and number of samples, for computing scan times
mjr 100:1ff35c07217c 131 uint64_t totalConversionTime;
mjr 100:1ff35c07217c 132 uint32_t nSamples;
mjr 100:1ff35c07217c 133
mjr 100:1ff35c07217c 134 // interrupt handler
mjr 100:1ff35c07217c 135 static PlungerSensorPot *isrThis;
mjr 100:1ff35c07217c 136 static void irq_handler_static(void) { isrThis->irq_handler(); }
mjr 100:1ff35c07217c 137
mjr 100:1ff35c07217c 138 void irq_handler()
mjr 100:1ff35c07217c 139 {
mjr 100:1ff35c07217c 140 // read the next sample
mjr 100:1ff35c07217c 141 uint16_t sample = pot.read_u16();
mjr 100:1ff35c07217c 142
mjr 100:1ff35c07217c 143 // deduct the outgoing sample from the running sum
mjr 100:1ff35c07217c 144 running_sum -= history[history_write_idx];
mjr 100:1ff35c07217c 145
mjr 100:1ff35c07217c 146 // add the new sample into the running sum
mjr 100:1ff35c07217c 147 running_sum += sample;
mjr 100:1ff35c07217c 148
mjr 100:1ff35c07217c 149 // store the new sample in the history
mjr 100:1ff35c07217c 150 history[history_write_idx++] = sample;
mjr 100:1ff35c07217c 151
mjr 100:1ff35c07217c 152 // wrap the history index at the end of the window
mjr 100:1ff35c07217c 153 if (history_write_idx >= countof(history))
mjr 100:1ff35c07217c 154 history_write_idx = 0;
mjr 100:1ff35c07217c 155
mjr 100:1ff35c07217c 156 // calculate the elapsed time since the last sample
mjr 100:1ff35c07217c 157 uint32_t now = timer.read_us();
mjr 100:1ff35c07217c 158 totalConversionTime += now - current_timestamp;
mjr 100:1ff35c07217c 159 ++nSamples;
mjr 100:1ff35c07217c 160
mjr 100:1ff35c07217c 161 // update the reading timestamp
mjr 100:1ff35c07217c 162 current_timestamp = now;
mjr 100:1ff35c07217c 163 }
mjr 100:1ff35c07217c 164
mjr 100:1ff35c07217c 165 // Running sum of readings. This is the sum of the readings in the
mjr 100:1ff35c07217c 166 // rolling 5ms window.
mjr 100:1ff35c07217c 167 uint32_t running_sum;
mjr 100:1ff35c07217c 168
mjr 100:1ff35c07217c 169 // Rolling window of readings, for the averaging filter. Our
mjr 100:1ff35c07217c 170 // sampling time is about 37.33us; 128 of these add up to about
mjr 100:1ff35c07217c 171 // 4.8ms, which is a good interval between samples for our
mjr 100:1ff35c07217c 172 // internal tracking and sending USB data to the PC.
mjr 100:1ff35c07217c 173 uint16_t history[128];
mjr 100:1ff35c07217c 174 int history_write_idx;
mjr 100:1ff35c07217c 175
mjr 100:1ff35c07217c 176 // current average reading and scan time
mjr 100:1ff35c07217c 177 uint32_t current_timestamp;
mjr 17:ab3cec0c8bf4 178 };