ATtiny Does 170×240 VGA With 8 Colors

The Arduino is a popular microcontroller platform for getting stuff done quickly: it’s widely available, there’s a wealth of online resources, and it’s a ready-to-use prototyping platform. On the opposite end of the spectrum, if you want to enjoy programming every bit of the microcontroller’s flash ROM, you can start with an arbitrarily tight resource constraint and see how far you can push it. [lucas][Radical Brad]’s demo that can output VGA and stereo audio on an eight-pin DIP microcontroller is a little bit more amazing than just blinking an LED.

[lucas][RB] is using an ATtiny85, the larger of the ATtiny series of microcontrollers. After connecting the required clock signal to the microcontroller to get the 25.175 Mhz signal required by VGA, he was left with only four pins to handle the four-colors and stereo audio. This is accomplished essentially by sending audio out at a time when the VGA monitor wouldn’t be expecting a signal (and [lucas][Rad Brad] does a great job explaining this process on his project page). He programmed the video core in assembly which helps to optimize the program, and only used passive components aside from the clock and the microcontroller.

Be sure to check out the video after the break to see how a processor with only 512 bytes of RAM can output an image that would require over 40 KB. It’s a true testament to how far you can push these processors if you’re determined. We’ve also seen these chips do over-the-air NTSC, bluetooth, and even Ethernet.

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Audio Effects on the Intel Edison

With the ability to run a full Linux operating system, the Intel Edison board has more than enough computing power for real-time digital audio processing. [Navin] used the Atom based module to build Effecter: a digital effects processor.

Effecter is written in C, and makes use of two libraries. The MRAA library from Intel provides an API for accessing the I/O ports on the Edison module. PortAudio is the library used for capturing and playing back audio samples.

F9GW4Y4IGQFYP23.MEDIUMTo allow for audio input and output, a sound card is needed. A cheap USB sound card takes care of this, since the Edison does not have built-in hardware for audio. The Edison itself is mounted on the Edison Arduino Breakout Board, and combined with a Grove shield from Seeed. Using the Grove system, a button, potentiometer, and LCD were added for control.

The code is available on Github, and is pretty easy to follow. PortAudio calls the audioCallback function in when it needs samples to play. This function takes samples from the input buffer, runs them through an effect’s function, and spits the resulting samples into the output buffer. All of the effect code can be found in the ‘effects’ folder.

You can check out a demo Effecter applying effects to a keyboard after the break. If you want to build your own, an Instructable gives all the steps.

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Code Craft-Embedding C++: Hidden Activities?

What is an embedded system? The general definition is a computer system dedicated to a specific purpose, i.e. not a general purpose system usable for different tasks. That is a very broad definition. I was just skimming the C++ coding guidelines for the Joint Strike Fighter. That’s a pretty big embedded system and the first DOD project that allowed C++! When you use an ATM to get money you’re using an embedded system. Those are basically hardened PCs. Then at the small end we have all the Internet of Things (IoT) gadgets.

The previous articles about embedding C++ discussing classes, virtual functions, and macros garnered many comments. I find both the positive and critical comments rewarding. More importantly, the critical comments point me toward issues or questions that need to be addressed, which is what got me onto the topic for this article. So thank you, all.

Let’s take a look at when embedded systems should or should not use C++, taking a hard look at the claim that there may be hidden activities ripe to upset your carefully planned code execution.

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Object Oriented State Machine Operating System Goes Open Source

On a desktop computer, you think of an operating system as a big piece of complex software. For small systems (like an Arduino) you might want something a lot simpler. Object Oriented State Machine Operating System (OOSMOS) is a single-file and highly portable operating system, and it recently went open source.

OOSMOS has a unique approach because it is threadless, which makes it easy to use in memory constrained systems because there is no stack required for threads that don’t exist. The unit of execution is a C++ object (although you can use C) that contains a state machine.

You can read the API documentation online. Just remember that this is not an end user OS like Windows or Linux, but an operating environment for managing multiple tasks. You can, though, use OOSMOS under Windows or Linux as well as many other host systems.

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Code Craft – Embedding C++: Timing Virtual Functions

Embedded C developers shy away from C++ out of concern for performance. The class construct is one of their main concerns. My previous article Code Craft – Embedding C++: Classes explored whether classes cause code bloat. There was little or no bloat and what is there assures that initialization occurs.

Using classes, and C++ overall, is advantageous because it produces cleaner looking code, in part, by organizing data and the operations on the data into one programming structure. This simple use of classes isn’t the raison d’etre for them but to provide inheritance, or more specifically polymorphism, (from Greek polys, “many, much” and morphē, “form, shape”).

Skeptics feel inheritance simply must introduce nasty increases in timing. Here I once more bravely assert that no such increases occur, and will offer side-by-side comparison as proof.

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Code Craft – Embedding C++: Classes

For many embedded C developers the most predominate and questionable feature of C++ is the class. The concern is that classes are complex and therefore will introduce code bloat and increase runtimes in systems where timing is critical. Those concerns implicate C++ as not suitable for embedded systems. I’ll bravely assert up front that these concerns are unfounded.

When [Bjarne Stroustrup] created C++ he built it upon C to continue that language’s heritage of performance. Additionally, he added features in a way that if you don’t use them, you don’t pay for them.

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Code Craft: Using Eclipse for Arduino Development

As we work on projects we’re frequently upgrading our tools. That basic soldering iron gives way to one with temperature control. The introductory 3D printer yields to one faster and more capable. One reason for this is we don’t really understand the restrictions of the introductory level tools. Sometimes we realize this directly when the tool fails in a task. Other times we see another hacker using a better tool and realize we must have one!.

The same occurs with software tools. The Arduino IDE is a nice tool for starting out. It is easy to use which is great if you have never previously written software. The libraries and the way it ties nicely into the hardware ecosystem is a boon.

When you start on larger projects, say you upgrade to a Due or Teensy for more code or memory space, the Arduino IDE can hamper your productivity. Moving beyond these limitations requires a new, better tool.

Where do we find a better tool? To begin, recognize, as [Elliot] points out that There is no Arduino “Language”, we’re actually programming in C or C++. We chose which language through the extension on the file, ‘c’ for C and ‘cpp’ for C++. An Arduino support library may be written in C or C++ depending on the developer’s preference. It’s all mix ‘n match.

Potentially any environment that supports C/C++ can replace the Arduino IDE. Unfortunately, this is not easy to do, at least for inexperienced developers, because it means setting up the language tool chain and tools for uploading to the board. A developer with that much experience might eschew an integrated development environment altogether, going directly to using makefiles as [Joshua] describes in Arduino Development; There’s a Makefile for That.

The reality is the Arduino IDE is not much more than a text editor with the ability to invoke the tools needed to compile and download the code to the Arduino. A professional IDE not only handles those details but provides additional capabilities that make the software development process easier.

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