c++

Remote Controlled Streaming Speakers

September 14, 2017 by 16 Comments

For want of a better use of a spare Raspberry Pi Zero W and a set of LogitechZ-680 surround sound speakers, [Andre van Kammen] hacked them together to make them stream music playing from his phone.

It was stumbling across the Pi Music Box distribution that really got the ball rolling, and the purchase of a pHAT DAC laid the foundation. Cracking open the speakers’ controller case, [Kammen] was able to get 5V of power off some terminals even when the speakers were on standby — awesome! — which the Pi could use. Power and volume are controlled via the Pi’s GPIO pins with a diode to drop the voltage and prevent shorts.

Now, how to tell whether the speakers are on or off? Well, a pin on the display connector changes to 4.3V when it’s on, so wiring a 10k resistor and a diode to said pin is a hackable solution. Finishing off the wired connections, it proved possible to cram the pHAT DAC inside the controller case with the GPIO header sticking out the back to mount the Pi upon with no other external wires — double awesome!

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Using Modern C++ Techniques with Arduino

May 5, 2017 by 96 Comments

C++ has been quickly modernizing itself over the last few years. Starting with the introduction of C++11, the language has made a huge step forward and things have changed under the hood. To the average Arduino user, some of this is irrelevant, maybe most of it, but the language still gives us some nice features that we can take advantage of as we program our microcontrollers.

Modern C++ allows us to write cleaner, more concise code, and make the code we write more reusable. The following are some techniques using new features of C++ that don’t add memory overhead, reduce speed, or increase size because they’re all handled by the compiler. Using these features of the language you no longer have to worry about specifying a 16-bit variable, calling the wrong function with NULL, or peppering your constructors with initializations. The old ways are still available and you can still use them, but at the very least, after reading this you’ll be more aware of the newer features as we start to see them roll out in Arduino code.
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FPGAs in C with Cynth

April 26, 2017 by 26 Comments

Programming an FPGA with Verilog looks a lot like programming. But it isn’t, at least not in the traditional sense. There have been several systems that aim to take C code and convert it into a hardware description language. One of these, cynth, is simple to use and available on GitHub. You will need to install scala and a build system called sbt, if you want to try it.

There are limitations, of course. If you want a preprocessor, you’ll have to run it separately. You can’t use global variables, multiplication, floats, and many other pieces of C. The compiler generates a Verilog file for each C function.
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FreeRTOS Gets Class

April 8, 2017 by 56 Comments

[Michael Becker] has been using FreeRTOS for about seven years. He decided to start adding some features and has a very interesting C++ class wrapper for the OS available.

Real Time Operating Systems (RTOS) add functionality for single-thread microcontrollers to run multiple programs at the same time without threatening the firmware developer’s sanity. This project adds C++ to the rest of the FreeRTOS benefits. We know that people have strong feelings one way or the other about using C++ in embedded systems. However, as the 24 demo projects illustrate, it is possible.

One nice thing about the library is that it is carefully documented. A large number of examples don’t hurt either. The library is clean with just under 30 classes. It seems to have resisted the trend of having classes for everything. You know the kind of library we mean. To create an Integer object, just build a configuration object to pass to the class factory generator which…. This library doesn’t entertain any of that. It has simple abstractions around threads and timers, queues, and mutexes.

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Tiny Tunes On An ATtiny13

November 24, 2016 by 8 Comments

When you take a microcontroller class in university, one of the early labs they have you drudge through on your way to, promised, mastery over all things embedded, is a tiny music generator.

It’s a more challenging lab than one would expect. It takes understanding the clock of the microcontroller and its sometimes temperamental nature. It takes a clear mental picture of interrupts, and is likely one of the first experiences a burgeoning designer will have worrying about the execution time of one of their loops. Also tables, data structures, and more. It even requires them to go out of their comfort zone a learn about an unrelated field, a challenge often faced in practicing engineering.

Luckily [Łukasz Podkalicki] has done a great job of documenting the adventure. He’s got everything from the schematic and code to the PWM traces on the oscilloscope.

It’s also worth mentioning that he’s got a few other really nice tutorials for the ATtiny13 microcontroller on his blog. A tiny party light generator and a IR receiver among them.

Think You Know C? Find Out

November 11, 2016 by 134 Comments

I’ve had the fortune or misfortune of interviewing a lot of job candidates over the years. It amazes me how often someone will claim to know something, sound reasonable, but then if you quiz them on it, it becomes really obvious that they don’t know much. To flush this out, we had a three-question test that would tell you a lot. People who got the right answer were ahead of the game, of course, but even looking at how people approached the answer (right or wrong) would tell you a lot, too.

I remember one case where the answer involved casting a value. A candidate had impressed me until faced with the question to which he said (more or less): “Well, there’s this function. I think it is called ‘cast’…” I think the look on my face told him that I actually knew the answer (not surprising, since I was giving the test) and that wasn’t it.

[Oleksandr Kaleniuk] has a C quiz of only five simple questions. They reminded me of at least one of my old company’s three-question quiz. I don’t want to say too much about the character of the test because I don’t want to give away the answers, but if you think you are a C wizard, go check it out. Then come back in the comments and tell us how you did. Just try to avoid posting spoilers (although you should probably avoid the comment section until you come back).

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Crack Mike Tyson’s Punch Out Bang Bang Passwords

November 11, 2016 by 5 Comments

[Bisqwit] has feelings about games that use exclamation points in his idiosyncratic walkthrough of all the nuances of the passwords in the famous Punch Out Bang Bang.

As he states in his deeply weird (though in no way wrong) channel intro, when he’s not driving a bus or teaching Israeli dance, he works hard to understand the things around him. Naturally, a mysterious phone number shaped set of digits in a favorite game was a secret worth extracting.

The digits can represent every possible state in the game.  It uses a pretty simple decoding and encoding scheme, which he walks through. As he says, it all becomes clear when you can see the source code.

After working through all the quirks he is able to arbitrarily generate any state in the game and handle the exceptions (such as Nintendo USA’s phone number). You can see all his code here and try it out for yourself. Video after the break.

We’ve grown to respect [Bisqwit] as the explainer of all things console games. You will like his explanation of how to write a code emulator for an NES CPU.

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