Posts with «microcontrollers» label

Arduino Gets a Command Line Interface

When using an Arduino, at least once you’ve made it past blinking LEDs, you might start making use of the serial connection to send and receive information from the microcontroller. Communicating with the board while it’s interacting with its environment is a crucial way to get information in real-time. Usually, that’s as far as it goes, but [Pieter] wanted to take it a step farther than that with his command line interpreter (CLI) for the Arduino.

The CLI allows the user to run Unix-like commands directly on the Arduino. This means control of GPIO and the rest of the features of the microcontroller via command line. The CLI communicates between the microcontroller and the ANSI/VT100 terminal emulator of your choosing on your computer, enabling a wealth of new methods of interacting with an Arduino.

The CLI requires a hex file to be loaded onto the Arduino that you can find at a separate site, also maintained by [Pieter]. Once that’s running, you can get all of that sweet command line goodness out of your Arduino. [Pieter] also has some examples on his project page, as well as the complete how-to to get this all set up and running. There’s a lot going on in the command line world, in Linux as well as windows. So there’s plenty to explore there as well.

Hack a Day 11 Nov 03:00
arduino  cli  command line  gpio  i2c  microcontrollers  serial  shell  unix  uno  

Weather Station Is A Tutorial in Low Power Design

Building your own weather station is a fun project in itself, but building it to be self-sufficient and off-grid adds another set of challenges to the mix. You’ll need a battery and a solar panel to power the station, which means adding at least a regulator and charge controller to your build. If the panel and battery are small, you’ll also need to make some power-saving tweaks to the code as well. (Google Translate from Italian) The tricks that [Danilo Larizza] uses in his build are useful for more than just weather stations though, they’ll be perfect for anyone trying to optimize their off-grid projects for battery and solar panel size.

When it comes to power conservation, the low-hanging fruit is plucked first. [Danilo] set the measurement intervals to as long as possible and put the microcontroller (a NodeMCU) to sleep in between. Removing the power from the sensors when the microcontroller was asleep was another easy step, but the device was still crashing overnight. Then he turned to a hardware solution and added a more efficient battery charger to the setup, which saved even more power. This is all the more impressive because the station communicates via WiFi which is notoriously difficult to run in low-power applications.

Besides the low power optimizations, the weather station itself is interesting for its relative simplicity. It could be built with things most of us have knocking around. Best of all, [Danilo] published the source code on his site, so most of the hard work has been done already. If you’re thinking he seems a little familiar, it’s because we’ve featured some of his projects before, like his cheap WiFi extender antenna and his homemade hybrid tube amplifier.

Want to Learn Ethernet? Write Your Own Darn AVR Bootloader!

There’s a school of thought that says that to fully understand something, you need to build it yourself. OK, we’re not sure it’s really a school of thought, but that describes a heck of a lot of projects around these parts.

[Tim] aka [mitxela] wrote kiloboot partly because he wanted an Ethernet-capable Trivial File Transfer Protocol (TFTP) bootloader for an ATMega-powered project, and partly because he wanted to understand the Internet. See, if you’re writing a bootloader, you’ve got a limited amount of space and no device drivers or libraries of any kind to fall back on, so you’re going to learn your topic of choice the hard way.

[Tim]’s writeup of the odyssey of cramming so much into 1,000 bytes of code is fantastic. While explaining the Internet takes significantly more space than the Ethernet-capable bootloader itself, we’d wager that you’ll enjoy the compressed overview of UDP, IP, TFTP, and AVR bootloader wizardry as much as we did. And yes, at the end of the day, you’ve also got an Internet-flashable Arduino, which is just what the doctor ordered if you’re building a simple wired IoT device and you get tired of running down to the basement to upload new firmware.

Oh, and in case you hadn’t noticed, cramming an Ethernet bootloader into 1 kB is amazing.

Speaking of bootloaders, if you’re building an I2C slave device out of an ATtiny85¸ you’ll want to check out this bootloader that runs on the tiny chip.

Demystifying The ESP8266 With A Series Of Tutorials

If your interest has been piqued by the inexpensive wireless-enabled goodness of the ESP8266 microcontroller, but you have been intimidated by the slightly Wild-West nature of the ecosystem that surrounds it, help is at hand. [Alexander] is creating a series of ESP8266 tutorials designed to demystify the component and lead even the most timid would-be developer to a successful first piece of code.

If you cast your mind back to 2014 when the ESP8266 first emerged, it caused great excitement but had almost no information surrounding it. You could buy it on a selection of modules, but there were no English instructions and no tools to speak of. A community of software and hardware hackers set to work, resulting in a variety of routes into development including the required add-ons to use the ever-popular Arduino framework. Four years later we have a mature and reliable platform, with a selection of higher-quality and well supported boards to choose from alongside that original selection.

The tutorials cover the Arduino and the ESP, as well as Lua and the official SDK. They are written for a complete newcomer, but the style is accessible enough that anyone requiring a quick intro to each platform should be able to gain something.

Our community never ceases to amaze us with the quality of the work that emerges from it. We’ve seen plenty of very high quality projects over the years, and it’s especially pleasing to see someone such as [Alexander] giving something back in this way. We look forward to future installments in this series, and you should keep an eye out for them.

Hack a Day 26 Aug 18:01

Simulate PIC and Arduino/AVR Designs with no Cloud

I’ve always appreciated simulation tools. Sure, there’s no substitute for actually building a circuit but it sure is handy if you can fix a lot of easy problems before you start soldering and making PCBs. I’ve done quite a few posts on LTSpice and I’m also a big fan of the Falstad simulator in the browser. However, both of those don’t do a lot for you if a microcontroller is a major part of your design. I recently found an open source project called Simulide that has a few issues but does a credible job of mixed simulation. It allows you to simulate analog circuits, LCDs, stepper and servo motors and can include programmable PIC or AVR (including Arduino) processors in your simulation.

The software is available for Windows or Linux and the AVR/Arduino emulation is built in. For the PIC on Linux, you need an external software simulator that you can easily install. This is provided with the Windows version. You can see one of several videos available about an older release of the tool below. There is also a window that can compile your Arduino code and even debug it, although that almost always crashed for me after a few minutes of working. As you can see in the image above, though, it is capable of running some pretty serious Arduino code as long as you aren’t debugging.

Looks and sounds exciting, right? It is, but be sure to save often. Under Linux, it seems to crash pretty frequently even if you aren’t debugging. It also suffers from other minor issues like sometimes forgetting how to move components. Saving, closing the application, and reopening it seems to fix that. Plus, we assume they will squash bugs as they are reported. One of my major hangs was solved by removing the default (old) Arduino IDE and making sure the most recent was on the path. But the crashing was frequent and seemed more or less random. It seemed that I most often had crashes on Linux with occasional freezes but on Windows it would freeze but not totally crash.

Basic Operation

The basic operation is pretty much what you’d expect. The window is broadly divided into three panes. The leftmost pane shows, by default, a palette of components. You can use the vertical tab strip on the left to also pick a memory viewer, a property inspector, or a file explorer.

The central pane is where you can draw your circuit and it looks like a yellow piece of engineering paper with a grid. Along the top are file buttons that do things like save and load files.

You’ll see a similar row of buttons above the rightmost pane. This is a code editor and debugging window that can interface with the Arduino IDE. It looks like it can also interface with GCBasic for the PIC, although I didn’t try that.

You drag components from the left onto the circuit. Wiring isn’t a distinct operation. You just let the mouse float over the connection until the cursor makes a cross. Click and then drag to the connection point and click again. Sometimes the program forgets to make the cross cursor and then I’ve had to save and restart.

Most of the components are just what you think they are. There are some fun ones including a keypad, an LED matrix, text and graphic LCDs, and even stepper and servo motors. You’ll also find several logic functions, 7400-series ICs, and there are annotation tools like text and boxes at the very bottom. You can right click on a category and hide components you never want to see.

At the top, you can add a voltmeter, an ammeter, or an oscilloscope to your circuit. The oscilloscope isn’t that useful because it is small. What you really want to do is use a probe. This just shows the voltage at some point but you can right click on it and add the probe to the plotter which appears at the bottom of the screen. This is a much more useful scope option.

There are a few quirks with the components. The voltage source has a push button that defaults to off. You have to remember to turn it on or things won’t work well. The potentiometers were particularly frustrating. The videos of older versions show a nice little potentiometer knob and that appears on my Windows laptop, too. On Linux the potentiometer (and the oscilloscope controls) look like a little tiny joystick and it is very difficult to set a value. It is easier to right click and select properties and adjust the value there. Just note that the value won’t change until you leave the field.

Microcontroller Features

If that’s all there was to it, you’d be better off using any of a number of simulators that we’ve talked about before. But the big draw here is being able to plop a microcontroller down in your circuit. The system provides PIC and AVR CPUs that are supported by the simulator code it uses. There’s also four variants of Arduinos: the Uno, Nano, Duemilanove, and the Leonardo.

You can use the built-in Arduino IDE — just make sure you have the real Arduino software on your path and it is a recent version. Also, unlike the real IDE, it appears you must save your file before a download or debug will notice the changes. In other words, if you make a change and download, you’ll compile the code before the change if you didn’t save the file first. You don’t have to use the built-in IDE. You can simply right click on the processor and upload a hex file. Recent Arduino IDEs have an option to export a hex file, and that works with no problem.

When you have a CPU in your design, you can right click it and open a serial monitor port which shows virtual serial output at the bottom of the screen and lets you provide input.

The debugging mode is simple but works until it crashes. Even without debugging, there is an option to the left of the screen to watch memory locations and registers inside the CPU.

Overall, the Arduino simulation seemed to work quite well. Connecting to the Uno pins was a little challenging at certain scales and I accidentally wired to the wrong pin on more than one occasion. One thing I found odd is that you don’t need to wire the voltage to the Arduino. It is powered on even if you don’t connect it.

Besides the crashing, the other issue I had was with the simulation speed which was rather slow. There’s a meter at the top of the screen that shows how slow the simulation is compared to real-time and mine was very low (10% or so) most of the time. There is a help topic explaining that this depends if you have certain circuit elements and ways to improve the run time, but it wasn’t bad enough that I bothered to explore it.

My first thought was that it would be difficult to handle a circuit with multiple CPUs in it since the debugging and serial monitors are all set up for a single CPU. However, as the video below shows, you can run multiple instances of the program and connect them via a serial port connection. The only issue would be if you had a circuit where both CPUs were interfacing with interrelated circuitry (for example, an op amp summing two signals, one from each CPU).

A Simple Example

As an experiment, I created a simple circuit that uses an Uno. It generates two PWM signals, integrates them with an RC circuit and then either drives a load or drives a load through a bipolar emitter follower. A pot lets you set the PWM percentages which are compliments of each other (that is, when one is at 10% the other is at 90%). Here’s the circuit:

Along with the very simple code:

int v;

const int potpin=0;
const int led0=5;
const int led1=6;

void setup() {
Serial.begin(9600);
Serial.println("Here we go!");
}

void loop() {
int v=analogRead(potpin)/4;
Serial.println(v);
analogWrite(led0,v);
analogWrite(led1,255-v);
delay(250);
}

Note that if the PWM output driving the transistor drops below 0.7V or so, the transistor will shut off. I deliberately didn’t design around that because I wanted to see how the simulator would react. It correctly models this behavior.

There’s really no point to this other than I wanted something that would work out the analog circuit simulation as well as the Arduino. You can download all the files from GitHub, including the hex file if you want to skip the compile step.

If you use the built-in IDE on the right side of the screen, then things are very simple. You just download your code. If you build your own hex file, just right click on the Arduino and you’ll find an option to load a hex file. It appears to remember the hex file, so if you run a simulation again later, you don’t have to repeat that step unless you moved the hex file.

However, the IDE doesn’t remember settings for the plotter, the voltage switches, or the serial terminal. You’ll especially want to be sure the 5V power switch above the transistor is on or that part of the circuit won’t operate correctly. You can right click on the Arduino to open the serial monitor and right click on the probes to bring back the plotter pane.

The red power switch at the top of the window will start your simulation. The screenshots above show close-ups of the plot pane and serial monitor.

Lessons Learned

This could be a really great tool if it would not crash so much. In all fairness, that could have something to do with my PC, but I don’t think that fully accounts for all of them. However, the software is still in pretty early development, so perhaps it will get better. There are a lot of fit and finish problems, too. For example, on my large monitor, many of the fonts were too large for their containers, which isn’t all that unusual.

The user interface seemed a little clunky, especially when you had to manipulate potentiometers and switches. Also, remember you can’t right-click on the controls but must click on the underlying component. In other words, the pot looks like a knob on top of a resistor. Right clicks need to go on the resistor part, not the knob. I also was a little put off that you can’t enter multiplier suffixes directly in component values. That is, you can’t enter a resistor value as 1K. You can enter 1000 or you can enter 1 and then change the units in a separate field to Kohms. But that’s not a big deal. You can get used to all of that if it would quit crashing.

I really wanted the debugging feature to work. While you can debug directly with simuavr or other tools, you can’t easily simulate all your I/O devices like you can with this tool. I’m hoping that becomes more robust in the future. Under Linux it would work for a bit and crash. On Windows, I never got it to work.

As I always say, though, simulation is great, but the real world often leads to surprises that don’t show up in simulation. Still, a simulation can help you clear up a host of problems before you commit to heating up the soldering iron or pulling out the breadboard. Simuide has the potential to be a great tool for simulating the kind of designs we see most on Hackaday.

If you want to explore other simulation options, we’ve talked a lot about LTSpice, including our Circuit VR series. There’s also the excellent browser-based Falstad simulator.

Ask Hackaday Answered: The Tale of the Top-Octave Generator

We got a question from [DC Darsen], who apparently has a broken electronic organ from the mid-70s that needs a new top-octave generator. A top-octave generator is essentially an IC with twelve or thirteen logic counters or dividers on-board that produces an octave’s worth of notes for the cheesy organ in question, and then a string of divide-by-two logic counters divide these down to cover the rest of the keyboard. With the sound board making every pitch all the time, the keyboard is just a simple set of switches that let the sound through or not. Easy-peasy, as long as you have a working TOG.

I bravely, and/or naïvely, said that I could whip one up on an AVR-based Arduino, tried, and failed. The timing requirements were just too tight for the obvious approach, so I turned it over to the Hackaday community because I had this nagging feeling that surely someone could rise to the challenge.

The community delivered! Or, particularly, [Ag Prismatic]. With a clever approach to the problem, some assembly language programming, and an optional Arduino crystalectomy, [AP]’s solution is rock-solid and glitch-free, and you could build one right now if you wanted to. We expect a proliferation of cheesy synth sounds will result. This is some tight code. Hat tip!

Squeezing Cycles Out of a Microcontroller

Let’s take a look at [AP]’s code. The approach that [AP] used is tremendously useful whenever you have a microcontroller that has to do many things at once, on a rigid schedule, and there’s not enough CPU time between the smallest time increments to do much. Maybe you’d like to control twelve servo motors with no glitching? Or drive many LEDs with binary code modulation instead of primitive pulse-width modulation? Then you’re going to want to read on.

There are two additional tricks that [AP] uses: one to fake cycles with a non-integer number of counts, and one to make the AVR’s ISR timing absolutely jitter-free. Finally, [Ag] ended up writing everything in AVR assembly language to make the timing work out, but was nice enough to also include a C listing. So if you’d like to get your feet wet with assembly, this is a good start.

In short, if you’re doing anything with hard timing requirements on limited microcontroller resources, especially an AVR, read on!

Taking Time to Think

The goal of the top-octave generator is to take an input clock and divide it down into twelve simultaneous sub-clocks that all run independently of each other. Just to be clear, this means updating between zero and twelve GPIO pins at a frequency of 1 MHz or so — updating every twenty clock cycles at the AVR’s maximum CPU speed. If you thought you could loop through twelve counters and decide which pins to flip in twenty cycles, you’d be mistaken.

But recognizing the problem is the first step to solving it. Although the tightest schedule might require flipping one pin exactly twenty clocks after flipping another, most of the time there are more cycles between pin updates — hundreds up to a few thousand. So the solution is to recognize when there is time to think, and use this time to pre-calculate a buffer full of next states.

[Ag]’s solution uses a few different loops that run exactly 20, 40, and 60 cycles each — the longer versions being just the 20-cycle one padded out with NOPs. These loops run inside an interrupt-service routine (ISR). When there are 80 or more cycles of thinking time until the next scheduled pin change, control is returned to the main loop and the next interrupt is set to re-enter the tight loops at the next necessary update time.

All the fast loop has to do is read two bytes, write them out to the GPIO pins, increment the pointer to the next row of data, and figure out if it needs to stall for 20 or 40 additional cycles, or set the ISR timer for longer delays and return to calculations. And this it can do in just twelve of the twenty cycles! Slick.

Buffers

Taking a step back from the particulars of the top-octave generator, this is a classic problem and a classic solution. It’s worth your time to internalize it, because you’ll run into this situation any time you have real-time constraints. The problem is that on average there’s more than enough time to complete the calculations, but that in the worst cases it’s impossible. So you split the problem in two parts: one that runs as fast as possible, and one that does the calculations that the fast section will need. And connecting together fast and slow processes is exactly why computer science gave us the buffer.

In [AP]’s code, this buffer is a table where each entry has two bytes for the state of the twelve GPIO pins, and one byte to store the number of clock cycles to delay until the next update. One other byte is left empty, yielding 64 entries or 256 bytes for the whole table. Why 256 bytes? Because the AVR has an 8-bit unsigned integer, wrapping around from the end of the table back to the beginning is automatic, saving a few cycles of wasteful if statements.

But even with this fast/slow division of labor, there is not much time left over for doing the pre-calculation. Sounding the highest C on a piano keyboard (4186 Hz) with a 20 MHz CPU clock requires toggling a GPIO pin every 2,390 cycles, so that’s the most time that the CPU will ever see. When the virtual oscillators are out of phase, this can be a lot shorter. By running the AVR at its full 20 MHz, and coding everything in assembly, [AP] can run the calculations fast enough to support twelve oscillators. At 16 MHz, there’s only time for ten, so every small optimization counts.

Some Optimization Required

Perhaps one of the cleverest optimizations that [AP] made is the one that makes this possible at all. The original top-octave chips divide down a 2 MHz square wave by a set of carefully chosen integer divisors. Running the AVR equivalent at 2 MHz resolution would mean just ten clocks per update and [AP]’s fast routine needed twelve, so the update rate would have to be halved. But that means that some odd divisors on the original IC would end up non-integral in the AVR code. For example, the highest C is reproduced in silicon as 2 MHz / 239, so to pull this off at 1 MHz requires counting up to 119.5 on an integer CPU. How to cope?

You could imagine counting to 119 half of the time, and 120 the other. Nobody will notice the tiny difference in duty cycle, and the pitch will still be spot on. The C programmer in me would want to code something like this:

uint8_t counter[12] = { 0, ... };
uint8_t counter_top[12] = { 119, ... };
uint8_t is_counter_fractional[12] = { 1, 0, ... };
uint8_t is_low_this_time[12] = { 0, ... };

// and then loop
for ( i=0 ; i<12; ++i){
  if ( counter[i] == 0 ){
    if ( is_counter_fractional[i] ){
      if ( is_low_this_time[i] ){
        counter[i] = counter_top[i];
    is_low_this_time = 0;
      else {
        counter[i] = counter_top[i] + 1;
    is_low_this_time = 1;
      }
    }
  }
}

That will work, but the ifs costs evaluation time. Instead, [AP] did the equivalent of this:

uint8_t counter[12] = { 0, ... };
uint8_t counter_top[12] = { 119, ... };
uint8_t phase[12] = { 1, 0, ... };

for ( i=0 ; i<12; ++i){
  if ( counter[i] == 0 ){
    counter[i] = counter_top[i] + phase[i];
    counter_top[i] = counter[i];
    phase[i] = -phase[i];
  }
}

What’s particularly clever about this construction is that it doesn’t need to distinguish between the integer and non-integer delays in code. Alternately adding and subtracting one from the non-integer values gets us around the “half” problem, while setting the phase variable to 0 means that the integer-valued divisors run unmodified, with no ifs.

The final optimization shows just how far [AP] went to make this AVR top-octave generator work like the real IC. When setting the timer to re-enter the fast loop in the ISR, there’s the possibility for one cycle’s worth of jitter. Because AVR instructions run in either one or two clock cycles, it’s possible that a two-cycle instruction could be running when the ISR timer comes due. Depending on luck, then, the interrupt will run four or five clocks later: see the section “Interrupt Response Time” in the AVR data sheet for details.

In a prologue to the ISR, [AP]’s code double-checks the hardware timer to see if it has entered on a one-cycle instruction, and adds in an extra NOP to compensate. This makes the resulting oscillator nearly jitter free, pushing out a possible source of 50 ns (one cycle at 20 MHz) slop. I don’t think you’d be able to hear this jitter, but the result surely looks pretty on the oscilloscope, and this might be a useful trick to know if you’re ever doing ultra-precise timing with ISRs.

The Proof of the Pudding

Naturally, I had to test out this code on real hardware. The first step was to pull a random Arduino-clone out of the closet and flash it in. Because “Arduinos” run at 16 MHz with the stock crystal, the result is that a nominal 440 Hz concert A plays more like a slightly sharp F, a musical third down. It sounds fine on its own, but you won’t be able to play along with any other instruments that are tuned to 440 Hz.

[AP]’s preferred solution is to run the AVR chip at 20 MHz. Since the hardware requirements are very modest, you could use a $0.50 ATTiny816 coupled with a 20 MHz crystal and you’d have a top-octave generator for literal pocket change — certainly cheaper than buying even an Arduino clone. I tested it out with an ATMega48P and a 20 MHz crystal on a breadboard because it’s what I had. Or you could perform crystalectomy on your Arduino to get it running at full speed.

We went back and forth via e-mail about all the other (firmware) options. [AP] had tried them all. You could trim the ISR down to 16 cycles and run at 16 MHz, but then there’s only enough CPU time in the main loop to support ten notes, two shy of a full octave. You could try other update rates than 1 MHz, but the divisors end up being pretty wonky. To quote [AP] from our e-mail discussion on the topic:

“After playing with the divider values from the original top octave generator IC and trying different base frequencies, it appears that the 2 MHz update rate is a “sweet spot” for getting reasonable integer divisors with < +/-2 cents of error. The original designers of the chip must have done the same calculations.”

To make a full organ out of this setup, you’ll also need twelve binary counter chips to divide down each note to fill up the lower registers of the keyboard, but these are easy to design with and cost only a few tens of cents apiece. All in all, thanks to [AP]’s extremely clever coding, you can build a fully-polyphonic noisemaker that spits out 96 simultaneous pitches, all in tune, for under $10. That’s pretty amazing.

And of course, I’ve already built a small device based on this code, but that’s a topic for another post. To be continued.

Energy Harvesting Design Doesn’t Need Sleep

Every scrap of power is precious when it comes to power harvesting, and working with such designs usually means getting cozy with a microcontroller’s low-power tricks and sleep modes. But in the case of the Ultra Low Power Energy Harvester design by [bobricius], the attached microcontroller doesn’t need to worry about managing power at all — as long as it can finish its job fast enough.

The idea is to use solar energy to fill a capacitor, then turn on the microcontroller and let it run normally until the power runs out. As a result, a microcontroller may only have a runtime in the range of dozens of microseconds, but that’s just fine if it’s enough time to, for example, read a sensor and transmit a packet. In early tests, [bobricius] was able to reliably transmit a 16-bit value wirelessly every 30 minutes using a small array of photodiodes as the power supply. That’s the other interesting thing; [bobricius] uses an array of BPW34 photodiodes to gather solar power. The datasheet describes them as silicon photodiodes, but they can be effectively used as tiny plastic-enclosed solar cells. They are readily available and can be arranged in a variety of configurations, while also being fairly durable.

Charging a capacitor then running a load for a short amount of time is one of the simplest ways to manage solar energy, and it requires no unusual components or fancy charge controllers. As long as the load doesn’t mind a short runtime, it can be an effective way to turn even indoor light into a figuratively free power source.

Mademoiselle Pinball Table Gets Rock ‘n Roll Makeover

Once upon a time, there was a music venue/artist collective/effects pedal company that helped redefine industry in Williamsburg, Brooklyn. That place was called Death By Audio. In 2014, it suffered a death by gentrification when Vice Media bought the building that DBA had worked so hard to transform. From the ashes rose the Death By Audio Arcade, which showcases DIY pinball cabinets made by indie artists.

Their most recent creation is called A Place To Bury Strangers (APTBS). It’s built on a 1959 Gottlieb Mademoiselle table and themed around a local noise/shoegaze band of the same name that was deeply connected to Death By Audio. According to [Mark Kleeb], this table is an homage to APTBS’s whiz-bang pinball-like performance style of total sensory overload. Hardly a sense is spared when playing this table, which features strobe lights, black lights, video and audio clips of APTBS, and a fog machine. Yeah.

[Mark] picked up this project from a friend, who had already cut some wires and started hacking on it. Nearly every bit of the table’s guts had to be upgraded with OEM parts or else replaced entirely. Now there’s a Teensy running the bumpers, and another Teensy on the switches. An Arduino drives the NeoPixel strips that light up the playfield, and a second Uno displays the score on those sweet VFD tubes. All four micros are tied together with Python and a Raspi 3.

If you’re anywhere near NYC, you can play the glow-in-the-dark ball yourself on July 15th at Le Poisson Rouge. If not, don’t flip—just nudge that break to see her in action. Did we mention there’s a strobe light? Consider yourself warned.

Want to get into DIY pinball on a smaller scale? Build yourself a sandbox and start playing.

Supersize DIY R/C Servos From Windscreen Wipers

We’re all familiar with the experience of buying hobby servos. The market is awash with cheap clones which have inflated specs and poor performance. Even branded servos often fail to deliver, and sometimes you just can’t get the required torque or speed from the small form factor of the typical hobby servo.

Enter [James Bruton] and his DIY RC servo from a windscreen wiper motor. Windscreen wiper motors are cheap as chips, and a classic salvage. The motor shaft is connected to a potentiometer via a pulley and some string, providing the necessary closed-loop feedback. Instead of using the traditional analog circuitry found inside a servo, an Arduino provides the brains. This means PID control can be implemented on the ‘duino, and tuned to get the best response from different load characteristics. There’s also the choice of different interfacing options: though [James]’ Arduino code accepts PWM signals for a drop-in R/C servo replacement, the addition of a microcontroller means many other input signal types and protocols are available. In fact, we recently wrote about serial bus servos and their numerous advantages.

We particularly love this because of the price barrier of industrial servomotors; sure, this kind of solution doesn’t have the precision or torque that off-the-shelf products provide, but would be sufficient for many hacks. Incidentally, this is what inspired one of our favourite open source projects: ODrive, which focuses on harnessing the power of cheap brushless motors for industrial use.

The Smaller, Tinier Arduino Platform

While many of the Arduino platforms are great tools for gaining easy access to microcontrollers, there are a few downsides. Price and availability may be the highest on the list, and for those reasons, some have chosen to deploy their own open-source Arduino-compatible boards.

The latest we’ve seen is the Franzininho, an Arduino Gemma-like board that’s based on the ATtiny85, a capable but tiny microcontroller by Atmel in a compact 8-pin configuration. This board has everything the Gemma has, including a built-in LED and breakout pins. One of the other perks of the Franzininho over the Gemma is that everything is based on through-hole components, making the assembly much easier than the surface mount components of the Gemma.

It’s worth noting that while these boards are open source, the Arduinos are as well. It’s equally possible to build your own 100% identical Arduino almost as easily. If you want more features, you can add your own by starting from one of these platforms and do whatever you want with it, like this semi-educational Atmel breakout board.

Thanks to [Clovis] for the tip!