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Giving the Arduino deques, vectors and streams with the standard template library

The Arduino IDE is extremely similar to C++, but judging from the sketches you can find on the Internet, you’d never know it. Simpler Arduino projects can make do with just toggling IO pins, reading values, and sending serial data between two points. More complex builds fall into the category of real software development, and this is where the standard Arduino IDE falls miserably short.

[Andy] saw this lack of proper libraries for more complicated pieces of software as a terrible situation and decided to do something about it. He ported the SGI Standard Template Library to bring all those fun algorithms and data structures to any AVR chip, including the Arduino.

Going over what’s included in [Andy]‘s port reads just like a syllabus for an object-oriented programming class. Stacks, queues, and lists make the cut, as do strings and vectors. Also included is just about everything in the   and headers along with a few Arduino-oriented additions like a hardware serial and liquid crystal streams.

With all these objects floating around, [Andy] says it will make an impact on Flash and SRAM usage in an AVR. Still, with all the hullabaloo over faster and larger ARM micros, it’s nice to see the classic 8-bit microcontroller becoming a bit more refined.

Using an oscilloscope as a composite video adapter

Confronted with a monitor that would display neither HDMI signal, nor composite video, [Joonas Pihlajamaa] took on a rather unorthodox task of getting his oscilloscope to work as a composite video adapter. He’s using a PicoScope 2204 but any hardware that connects to a computer and has a C API should work. The trick is in how his code uses the API to interpret the signal.

The first thing to do is make sure the voltage levels used in the composite signal are within the tolerances of your scope. [Joonas] used his multimeter to measure the center pole of the RCA connector and found that the Raspberry Pi board puts out from 200 mV to 2V, well within the PicoScope’s specs. Next he started to analyze the signal. The horizontal sync is easy to find, and he ignored the color information — opting for a monochrome output to ease the coding process. The next big piece of the puzzle is to ascertain the vertical sync so that he knows where each frame starts. He got it working and made one last improvement to handle interlacing.

The proof of concept video after the break shows off the he did. It’s a bit fuzzy but that’s how composite video looks normally.

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Library for driving SSD1289 LCD displays with small microcontrollers

[H. Smeitink] got his hands on a 320×240 color TFT LCD screen. He set out to drive it with a small PIC microcontroller but didn’t find a lot of help out there to get up and running quickly. This is surprising since it’s a really nice display for quite a low price (under $16 delivered on eBay at the time of writing). He decided to write his own library and support tools to help others.

The display includes an SPI touch screen, but since that works separately from the LCD controller, touch input is not supported in this package. The driver that he wrote is coming from a mikroC toolchain point of view, but it shouldn’t be too hard to port to your platform of choice. We took a quick look at the code and it seems all you need to do is tweak the defines to match your hardware registers, and implement your own delay_ms() function.

But he didn’t stop with the driver. You’ll also find a C# program which converts images to an array for easy use on the display. Incidentally, this is the same display which [Sprite_TM] got working with the Raspberry Pi.

Using the GPIO pins on a Raspberry Pi

In addition to being a serviceable single board computer, the Raspberry Pi also has a header full of GPIO pins at your beck and call. [Tedbot] sent in a great tutorial on using these pins with Python, Bash, and C.

The GPIO pins on the Raspi are arranged in a 2×13 header. Until Sparkfun manages to manufacture a decent Raspi protoboard, the easiest way to break these pins out is with an old IDE ribbon cable. After plugging the other end into a breadboard, [Tedbot] had an easily accessible set of Raspi pins.

To control these pins, [Tedbot] found two libraries: the first is WiringPi that implements a C-style, Arduino-like programming environment on the Raspi. The second is the RPi.GPIO Python package. Since the Raspi runs Linux, and everything in Unix is a file, [Tedbot] used a shell script to blink a LED.

One word of warning if you’re building a board to extend the capabilities of the Raspi: these pins aren’t 5 V tolerant, so you’ll need to throw in a buffer or level converter when building a Raspi circuit.

Edit: Adafruit is releasing a Pi Plate prototyping board in a few weeks. Neat, huh?

Monitor your heartbeat with a webcam and a flashlight

After seeing some heart rate monitor apps for Android which use the camera and flashlight features of the phones, [Tyson] took on the challenge of coding this for himself. But he’s not using a smart phone, instead he grabbed a headlamp and webcam for his heat rate monitor.

To start out he recorded a test video with his smart phone to see what it looks like to cover both the flash LED and camera module with his thumb. The picture is mainly pink, but there’s quite obviously a color gradient that pulses with each gush of blood through his skin. The next task was to write some filtering software that could make use of this type of image coming from a webcam. He used C# to write a GUI which shows the live feed, as well as a scrolling graph of the processed data. He took several tries at it, we’ve embedded one of the earlier efforts after the break.

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Arduino can program PIC too!

This is a wiring diagram that [Soranne] put together when developing a method of programming PIC microcontrollers using an Arduino board. You can see that he takes care of the 12V issue by connecting the Master Clear (MCLR) pin to an external source. This comes with one warning that the Arduino should always be reset just before making that connection.

He’s tested this with a 16F628 and is happy to report that he can successfully flash the program memory, but hasn’t implemented a way to write to the EEPROM as of yet. This should work for any of the 16F family of chips, but we’d bet this will be extended if some knowledgeable folks decide to lend a hand.

On the PC side of things [Soraane] has been working on a program to push code to the Arduino via the USB connection. He’s developing it in C# and even has a GUI worked up for the project. You can get your hands on the software in the second post of the thread linked above but you’ll have to be logged into the Arduino forum to see the download link.

We think the 12V issue is why we don’t see more roll-your-own programmers for PIC. But there are a few solutions out there like this ATmega8 version.

Trying to measure the speed of light with an Arduino

We know that measuring the speed of light with an Arduino is possible. It’s just that the implementation is hard.

Last month we saw [Udo]‘s blinkenlight shield that can be used as a line scan camera. It’s a neat piece of kit, but [Udo] really wants to submit something for the Buildlounge laser cutter giveaway, so he figured measuring the speed of light would be an easy project. If a kid and a chocolate bar can do it, surely it can’t be too hard.

[Udo] hit upon the idea of pulsing a laser pointer and measuring the time of the reflection. Because his blinkenlight shield can be used as a light sensor, all that’s needed is a mirror and a pretty long line of sight. There’s a few problems with the setup though: with the Arduino running at 16 MHz, a photon will travel 19 meters in one clock cycle.

Even with some very clever coding, we’re not really sure detecting an emitted photon is possible at such (relatively) slow clock speeds. We’re thinking [Udo] could source a few hundred meters of optic fiber so the entire experiment could fit on a desk, but feel free to drop a note in the comments if you’ve got a better idea. [Udo]‘s demo of his blinkenlight/laser mashup is after the break.

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