www.youtube.com/watch?v=x7-wtJGhpzE

www.youtube.com/watch?v=0Bu621bRCZ8

www.youtube.com/watch?v=gubQbWLMAnI

Displaying a 64x64 pixel animation exported from a GIF Animation with a custom python script.

UPDATE: After some optimization in the animation loading, the set pixel functions and the display refresh function the Arduino is able to display about 50 frames per second when displaying a 96x64 monocolor animation from flash memory.

www.youtube.com/watch?v=kXHrMa2NvqM

The displays are connected to the Arduino to share the row select pins (A,B,C and D) and the control lines EN, CLK & LATCH. The serial lines R1,R2,G1,G2 have their dedicated pins. So there are 19 pins needed out of possible 20 (not counting the reset pins as I/O). As the displays are loaded in 16 rows a 64bit some transformation has to be done while loading the display. This limits the update rate hard. A possible way to improve the frame rate is moving the transformation to the function setting the pixels. Or maybe changing the connection scheme to common R1,R2,G1,G2 with separate EN & LATCH for each display which would result in 15 I/O pins needed but maybe suffer from slower update rate. As the display modules are chainable it is possible to connect them in series and load the 16 rows with 192bits each and using only 11  pins, but reducing the frame rate again. Since the ATMega328 cannot achieve high enough frame rates at any connection scheme I would suggest using the chained way.

What you get when combining those is a via USB controllable dotmatrix display. The PC related programming I did in Python using libusb and the python binding called pyusb. So the program should be cross platform compatible! Also python allows one to extend the functionality(e.g. checking for new mail, usb notifications of any type…) very easy.

Video after the break.

www.youtube.com/watch?v=6VcidXvYe6A

Download:

• usbmatrix

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

The LED Module is powered 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.

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