April 9th, 2009

Speaking AVR

speaking avr

Most of you already seen simple audio output trough the micro controller PWM channel, this project is very simple, and gives you a set of PC programs which are useful to convert plain text to audio stream. The firmware is basically a simple interface between the audio amplifier and PC, the data stream is received by the controller trough the serial port with 8kHz refresh rate and written directly to the PWM registers. The quality is poor but this device isn’t intended for hi-fi applications, although it is well suited for speech playback.

This can be a great alternative for LCD displays, since for mono audio you need only 1 output pin, you can seriously reduce the pin count of your application, the only disadvantage is the large memory needed to store the audio stream, luckily the SD cards are getting cheaper every day.

The 8kHz refresh rate shouldn’t pose any problem, even an 8 bit micro controller running on 8MHz clock can easily manage the SD card reading and PWM refresh, without major system overhead.

Speaking avr: [via] [link]

November 2nd, 2008

Flickr + Nokia LCD

Flickr + Nokia LCD

The project described below demonstrates the usage of LCD graphical display with the help of available demo source codes.

The LCD in the first place is a tricky device, first of all you need separate power for the back light because of the higher voltage, so the author used a break-out board from www.sparkfun.com (Nokia 6100 LCD including breakout board), this board has built in a DC/DC converter for boosting the voltage, you only need one 3.3V power source.

The second issue is the control of the LCD, fortunately these mass produced displays are well documented and frequently used by hobbyist, you find a bunch of demo code for almost any type of microcontroller. The author used the demo code found on the sparkfun site, with small modifications.

Let’s see the microcontroller, some years ago the favorite AVR used by newbies was the Atmega8, which was superseded by the Atmega48/88/168, it has the same rich features, and some improvements, this was the choice of the authors too(ATmega48).

After hooking up the LCD with the microcontroller, we need some data to display, the author used his flickr account for accessing some photos on the web, you can find the free API to access the data for phyton or other high level programming languages, the pictures after downloaded, were resized, and transferred via serial port to the microcontroller which displays the image. The rendering is quite slow because the data is sent pixel by pixel to the display, but hey, at the end you have a color picture downloaded from the web and displayed on a Nokia display.

Although it sounds to be great fun to build it, if you are a beginner, try something simpler, or at least load a simple picture from your PC.

Flickr + Nokia LCD: [Link]

Fetch Flickr Images On A Nokia LCD

Alex from Tinkerlog added an interesting article about fetching Flickr images on a Nokia LCD. He used a Nokia 6100 LCD including breakout board from Sparkfun. The MCU is an ATmega48, though cheap, not the best choice as he encountered some problems with the image quality. First the image is fetched from Flickr using Beej’s Python Flickr API than the image is resized and sent to the LCD. Taken to consideration the fact that this is his first LCD project we can call it a success.

Fetch Flickr Images On A Nokia LCD: [Link]

Wall clock that controlled trough IR also keeps your score

This ATmega48 based wall clock is able to keep any kind of score and display it on its 4 digits. The score is controlled by a IR remote control powered by an ATtiny28. Also trough the remote you can set the time and configure the clock. The digits are build on pcb with 5 mm LED’s, no commercial LED digits were used.

Wall clock that controlled trough IR also keeps your score: [Download Project][View Project PDF]

April 13th, 2008

Modular LED Matrix Display

Modular LED Matrix Display

This project presents us a modular matrix led display based on the ATmega48 micro-controller. The main feature of this modular matrix display is that you can reconfigure it to form an arbitrary lenght LED display. Due to the simplicity of the design, it is easy to extend the communications protocol to more than one display chain to increase the height of the display. In this project, both single and double row examples are shown.

Modular LED Matrix Display: [Download Project][View Project PDF]

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