Tobi’s Corner

What can you do with 100 common anode rgb leds? build a 8×8 matrix and interface it!

The circuit uses 74HC595 shift registers with output latch. each shiftregister interfaces one color + one shiftreg for the matrix rows. the interfaces uses 6 I/O lines for faster speed and easier interfacing. an avr running at 8MHz can update the matrix with 8 brightness levels displaying nice fading colors patterns or colored text (or both). the sample program creates fading color patterns using a sine table. for smoother display a double buffer was implemented.

Download: rgbmatrix.c

For my 7-segment display AVR clock i was searching for a way to keep the clock accurate. One option would be using a DCF77 standard time receiver. The module I had seemed to be broken so I decided to use an ethernet interface and NTP. For this I purchased a small ENC28J60 + AVR board from Simon Küppers. This small board is only about 38×30mm in size and includes an ATMega168, ENC28J60, Ethernet-Jack + Magnetics and a voltage regulator. The 14 available I/O Pins are connected to a standard 0.1″ header, so there are possibilities to extend the board.

(more…)

I’ve bought some 14cm high red 7-segment LED Displays on EBay and started to build a clock based on AVR ATTiny2313.

The circuit is build with an AVR ATTiny2313 a UDN2982 high side and a ULN2803 low side driver/switch

The LED Module is power with 18-20V to give a brighter display. The forward volatge of a single segment is about 13V. 13V + voltage loss at the switches (worst case 2V + 1.6V) is about 16.6V. I used 39Ohm resistors for the segments and so 16.6V + 39Ohm x 0.08A = 19.72V. Because of multiplexing 4 modules to get an avarage current of 20mA per segment the current has to be four times higher ( 20mA x 4 = 80mA ). The dots on the modules have a lower forward voltage resulting in a higher limiting resistor: (16.6V - 3.6V - 3.6V) / 80mA = 120Ohms.

AVRTer is not only a Terminal Emulation for AVR, it’s a Terminal build with an AVR.

The Terminal is build with an ATMega8 and a 640×240px GLCD. The Terminal can be used as a RS232 debugger.The Display Routines are from Holger Klabunde. Have a look at his Webpage: http://www.holger-klabunde.de/

The Keyboard routines are based on the ATMEL Application Note AVR313 and written by V. Brajer.

The ascii logo has been generated using this online ascii-generator.

Downloads:

• avrTer Sourcecode

avrDotmatrix uses a 5×7 dotmatrix display and an ATMega8 to create a nice display with scrolling!

avrDotmatrix - Is a 5×7 LED Matrix Display controlled by a ATMega8 to display scrolling text, time or temperatures. The pattern is generated with multiplexing the 5 matrix columns and setting the correct row bits.

This projects is still in development and i’m gonna add a temperature sensor (LM75), a I2C EEProm and maybe a IR receiver for transmitting texts to the display wireless.

Downloads:

• Sample Video
• avrDotmatrix Sourcecode