raspberry pi

1649 Articles

Code Craft: When #define Is Considered Harmful

October 16, 2015 by 95 Comments

An icon of Computer Science, [Edsger Dijkstra], published a letter in the Communications of the Association of Computer Machinery (ACM) which the editor gave the title “Go To Statement Considered Harmful“. A rousing debate ensued. A similar criticism of macros, i.e. #define, in C/C++ may not rise to that level but they have their own problems.

Macros are part of the preprocessor for the C/C++ languages which manipulates the source code before the actual translation to machine code. But there are risks when macros generate source code. [Bjarne Stroustrup] in creating C++ worked to reduce the need and usage of the preprocessor, especially the use of macros. In his book, The C++ Programming Language he writes,

Don’t use them if you don’t have to. Almost every macro demonstrates a flaw in the programming language, in the program, or in the programmer.

As C retrofitted capabilities of C++, it also reduced the need for macros, thus improving that language.

With the Arduino using the GNU GCC compilers for C and C++ I want to show new coders a couple of places where the preprocessor can cause trouble for the unwary. I’ll demonstrate how to use language features to achieve the same results more cleanly and safely. Of course, all of this applies equally when you use any of these languages on other systems.

We’re only going to be looking at macros in this article but if you want to read more the details about them or the preprocessor see the GNU GCC Manual section on the preprocessor.

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Hackaday Links: October 11, 2015

October 11, 2015 by 13 Comments

[Kratz] just turned into a rock hound and has a bunch of rocks from Montana that need tumbling. This requires a rock tumbler, and why build a rock tumbler when you can just rip apart an old inkjet printer? It’s one of those builds that document themselves, with the only other necessary parts being a Pizza Hut thermos from the 80s and a bunch of grit.

Boot a Raspberry Pi from a USB stick. You can’t actually do that. On every Raspberry Pi, there needs to be a boot partition on the SD card. However, there’s no limitation on where the OS resides,  and [Jonathan] has all the steps to replicate this build spelled out.

Some guys in Norway built a 3D printer controller based on the BeagleBone. The Replicape is now in its second hardware revision, and they’re doing some interesting things this time around. The stepper drivers are the ‘quiet’ Trinamic chips, and there’s support for inductive sensors, more fans, and servo control.

Looking for one of those ‘router chipsets on a single board’? Here you go. It’s the NixCoreX1, and it’s pretty much a small WiFi router on a single board.

[Mowry] designed a synthesizer. This synth has four-voice polyphony, 12 waveforms, ADSR envelopes, a rudimentary sequencer, and fits inside an Altoids tin. The software is based on The Synth, but [Mowry] did come up with a pretty cool project here.

Open Source FPGA Pi Hat

October 10, 2015 by 14 Comments

Over on Hackaday.io, [Dave Vandenbout] has posted the CAT board, a Raspberry Pi daughterboard hat that features a Lattice FPGA, 32 MB of RAM, EEPROM, and a few Grove and PMOD connectors. The CAT takes advantage of the open source tool chain available for Lattice including the Python-based MyHDL (although, you could just use Verilog directly, if you prefer) and Icestorm. One interesting point: you can run the tool chain on the Raspberry Pi, resulting in a self-contained and largely portable FPGA development environment.

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Latest Raspberry Pi Images Have Improved Scratch

October 8, 2015 by 12 Comments

Not everyone likes Scratch — the block-oriented programming language that MIT developed to help kids program. While dyed-in-the-wool programmers probably find it limiting, it can be an effective way to teach basic programming to newcomers and there are some people who enjoy the graphical style of programming.

The latest Raspbian release (the operating system image for Raspberry Pi) has a new and improved version of Scratch for those who want to use it on the Pi. According to the Raspberry Pi blog, the new version is up to ten times faster than previous versions and also includes an improved method for Scratch programs to access the board’s general purpose I/O and other I/O devices.

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Raspberry Pi Sentry Turret Is The Enemy Of All Mankind

October 3, 2015 by 20 Comments

War, huh, what is it good for? Absolutely nothing, except as an excuse to build a Raspberry Pi powered sentry turret that will track and fire upon your enemies. That’s what [Matt Desmaris] decided to do, and he has released the full details of his build.

It lacks the polished elegance of most military hardware, but what do you expect of a quick and dirty hack? It’s not shiny or ominous, but it has that killer motion-tracking feature. [Matt] is using OpenCV to detect movement from a USB webcam, two servos to pan and tilt the camera and gun and a small relay to pull the trigger. Manual control over the Interwebs is also available.

We’ve seen lots of similar builds using weaponry such as rubber bands and Nerf guns, but this one is a great start if you are interested in seeing how you can tie together tools like OpenCV and servos to create a camera that actively tracks movement.

A Third Scale Mini PowerMac

October 2, 2015 by 12 Comments

We’re surrounded by tiny ARM boards running Linux, and one of the most popular things to do with these tiny yet powerful computers is case modding. We’ve seen Raspberry Pis in Game Boys, old Ataris, and even in books. [Aaron] decided it was time to fit a tiny computer inside an officially licensed bit of miniature Apple hardware and came up with the Mini PowerMac. It’s a 1/3rd scale model of an all-in-one Mac from 1996, and [Aaron] made its new hardware fit like a glove.

Instead of an old Mac modified with an LCD, or even a tiny 3D printed model like Adafruit’s Mini Mac Pi, [Aaron] is using an accessory for American Girl dolls released in 1996. This third-scale model of an all-in-one PowerPC Mac is surprisingly advanced for something that would go in a doll house. When used by American Girl dolls, it has a 3.25″ monochrome LCD that simulates the MacOS responding to mouse clicks and keypresses. If you want to see the stock tiny Mac in action, here’s a video.

The American Girl Mini Macintosh is hollow, and there’s a lot of space in this lump of plastic. [Aaron] tried to fit a Raspberry Pi in the case. A Pi wouldn’t fit. An ODROID-W did, and with a little bit of soldering, [Aaron] had a computer far more powerful than an actual PowerMac 5200. Added to this is a 3.5″ automotive rearview display, carefully mounted to the 1/3rd size screen bezel of the mini Mac.

The rest of the build is exactly what you would expect – a DC/DC step down converter, a USB hub, and a pair of dongles for WiFi and a wireless keyboard. The software for the ODROID-W is fully compatible with the Raspberry Pi, and a quick install of the Basilisk II Macintosh emulator and an installation of Mac OS 7.5.3 completed the build.

Raspberry Pi 2 Game Boy Brings Sexy Back From 1989

October 1, 2015 by 18 Comments

When the ever-versatile Raspberry Pi was released, the potential for cheap video game emulation was immediately obvious. Some of the very first Raspi projects to hit the internet were arcade cabinets, and it wasn’t long until people were making them portable. A purpose-build Linux distort called RetroPie has become very popular specifically because of the Raspi’s game-emulation potential. However, the actual hardware for these emulation systems isn’t always the most aesthetically (or ergonomically) pleasing. That’s where reddit user [Cristov9000] has managed to stand out from the crowd.

[Cristov9000] accomplished this by combining high-quality design (and 3D printing) with the careful use of original Nintendo parts. Game Boy and SNES buttons and elastomers were used to achieve the correct button feel. Other original Game Boy parts, like the volume wheel and power switch, ensure that the system feels as much like 1989 OEM hardware as possible.

Also impressive is the internal hardware, including 3 custom PCBs used to tie everything together to work via the Raspberry Pi 2 GPIO pins. The display is a 3.5″ TFT screen, and with the 6000 mAh it can handle gameplay for more than 7 hours. Other details, like the integrated mono speaker and rear shoulder buttons complete the experience. Combined with the RetroPie and an assortment of emulators, this is one of the most impressive portable gaming builds we’ve seen, especially among a crowded list of awesome raspi-based Game Boy builds.