Category Archives: AVR Microcontrollers

This project was born for repairing broken PC monitors. This allows to avoid using a computer while testing monitor patterns. The Tiny monitor tester uses ATTiny2313 AVR MCU running at 20MHz speed. Such speed allows running synchro H and V signals directly form MCU ports. Also circuit converts R,G,B signals to analog using simple R-2R resistor network.

ATTiny2313 Monitor tester:

• can generate 8 different raster images;

• supports resolutions of 640x480x60Hz, 800x600x60Hz, 1024x768x60Hz;

• is near to credit card size;

• DC adapter or battery powered;

Circuit can be viewed here and single sided PCB

One of test patterns on LCD monitor:

I think it is a good device for testing used monitors when buying them in a public market. You don’t need a PC, just plug Tiny Monitor tester and you will see if there are any damages, are all colors working, dead pixels on LCD’s, are different resolutions OK and so on. This thing should be included to a must-to build list.

You can download ready to burn hex software and AVRASM source file in single archive.

Deogen - Tiny monitor tester

This project is made by HÃ¥kon A. Hjortland. The idea is pretty simple and original. He used rotating mirrors to create a video projection. 16 differently tilted mirrors were fixed on a round drum that spins at about 20 – 30 s^-1. Each mirror draw a separate line on a screen. For each pixel, the laser is turned on or off. Resolution isn’t very bit -just 16 pixels at each line. But it gives a nice impression.

As Author states calibration is a hardest part of project. Especially Y direction of mirrors, that each mirror draw a separate line on screen. X calibration is done by software.

The fun part is a Firmware. Program is written in AVR-GCC language. What it does is redraws a frame every 4 or 5 frames.

Watch a video of this project: DivX video: projector.avi (3.5 MiB)

Source code:

projector.c
video_alf.h
test_pattern.h

Additional sources representing an idea:

Building a Laser Projector (PDF) – By Alex Hornstein
TinyProjector – Eight lasers and mirror

Original source by HÃ¥kon A. Hjortland.

Related

To project your photo from a digital camera, first add your photo to your computer. A wireless webcam could also take a great picture. Transfer the photo file to a laser video projector according to the user guide. In no matter than minutes, you’ll have your very own home theater.

This is pretty old circuit but I found it interesting to describe here.

24×24 LED display is formed by using 9 8×8 Dot LED matrix displays, that are connected to AT90S2313 MCU. MCU scans an indicator lines in series. Special PC program is written which allows drawing images on screen and transfer them via COM port to device. You can send images in series what gives an animation effect.

Device circuit:

Circuit is was built using obsolete AT90S2313 MCU which can be replaced by Attiny2313 MCU with minor modifications of firmware.

To make program work you event don’t need to connect device to computer COM port. You can store images in other master MCU EEPROM memory Each received byte from UART is immediately sent to 8 LEDs, second byte to next 8 LEDs and so on. Bytes has to be sent one by one without delay. USART is working at 115200 baud, 8bits, no parity.

Demo movie (137kB);

Source code

Originals source svv.on.ufanet.ru

Choice of the microcontroller oscillator depends on many factors. Before choosing one you should consider: Cost, accuracy and environmental parameters. Clock sources can be grouped in two major groups: based on mechanical resonance(crystals and ceramic resonators) and RC (resistor, capacitor) oscillators.

Most popular form of mechanical resonant generators in microcontrollers are Pierce oscillators:

Ceramic and crystal based generators provide very high accuracy and low temperature coefficient. But they have slower startup comparing to RC generators. But RC generator’s accuracy suffer from temperature variations and supply voltage. Nominal frequency can variate from 5% to 50%:

Oscillator stability can be expressed in figures as ‘±20ppm’ what means 20 parts per million. How to understand this? Imagine that there are 32 million seconds per year. Then in every million seconds generator may miss 20 seconds. SO over a year generator will miss 32×20 seconds, what is around 10 minutes. Standard crystals are rated from ±10ppm to ±100ppm what means from 5 to 50 minutes a year.

What to do is you want more stability. One issue would be to calibrate oscillator and keep it all time in constant temperature like in fridge. But it is not practical. There is another option – Temperature Compensated Crystal Oscillators (TCXO). These oscillators in their package include circuitry that is responsible for temperature compensation. Such devices can provide stability to up to ±0.1ppm, what means around 1 minute every 20 years. But…these crystals are expensive (can be about 100$ cost).

You don’t always have to buy TCXO – sometimes you may add temperature sensor and adjust timing according to temperature.

Other disadvantages of crystals are that they are susceptible to vibrations and they loose stability with the age.

To reduce vibration affect you may chose to use ceramic resonators. They may not be damaged by vibrations as crystals can, but they have much lower stability- typically ±5000ppm what means about 50 minutes/week.

If you are windows user, there is an easiest solution to program Atmega128 microcontrollers. In http://piconomic.co.za there is nice bootloader binary you can download and use for personal purposes.

First of all you will need to upload bootloader hex file (which is packed in) to Atmega128 and properly program fuses. For my Piconomic board I set fuses like this:

Then plug RS232 cable to computer COM2 (or COM1) port and then from windows select Start->All Programs->Accessories->Communication->HyperTerminal. HyperTerminal is program used for multiple communication purposes like connecting to other computer, telnet, modems and null modems.

Firs of all select connection type – COM2:

After pressing OK you will be taken to COM2 connection properties:

After connection settings are done it is time to start bootloading. I have never thought it can be so easy. Just select Transfer->Send file in HyperTerminal program:

In the opening window select file you want to download. Just remember that binary has to be compiled as BIN not HEX. Second option is to select protocol – how data will be sent to booloader. Bootloader is programmed to support Xmodem protocol:

Press Send button then Hyperterminal starts waiting for bootloader to respond:

Just press “Reset” button on your target board and sending will begin automatically. After sending of bin is finished program starts to execute uploaded program.

The AVR fuse bits have been set so that execution starts from the boot vector address. This means that the bootloader will always be executed first. The bootloader sends a ‘C’ character to start a transfer and waits for 1 second for a valid XMODEM-CRC data packet. If the transfer is not successful, it will jump to address 0×0000 and execute the application. This is why we start sending from Hyperterminal first and then press Reset button.

Good news for Linux lovers. The new IDE development software for AVR microcontrollers has shown up. This is KDE based IDE under GPL. It is fully-featured editor which includes serial terminal for debugging, uses AVR-GCC compiler, uisp for serial downloading and avrdude programming software.

Few screen-shots of this tool:

This is first release but is is already ready to start developing AVR projects. I think it’s a nice beginning. Download and try KontrollerLab from http://sourceforge.net/projects/kontrollerlab/

Atmel’s new devices are 20-pin tiny-AVR microcontrollers with high-speed timers.
All three devices are pin-compatible, differing only in the size Flash, EEPROM and SRAM memories.

• The ATtiny261 has 2 Kbytes of self-programmable Flash memory;
• The ATtiny461 has 4 Kbytes of self-programmable Flash memory;
• The ATtiny861 has 8 Kbytes of self-programmable Flash memory.

All devices deliver 20 MIPS throughput when running at maximum 20 Mhz frequency.
The internal 8 MHz RC oscillator and the on-chip PLL can run the 10-bit timer/counter up to 64 Mhz speed. The high-speed timer/counter with three independent PWM generators is ideal for battery chargers, battery monitoring, power monitoring and motor-control applications. All devices have internal EEPROM, pull-up resistors, an internal 8 MHz precision oscillator and 12 general I/O pins for application use. Alternatively, the I/O pins work as ADC inputs or PWM outputs.
ATtiny261, ATtiny461 and ATtiny861 are available in 20-pin SOIC and PDIP and 32-pad QFN packages.