Recent Post

PAL Colour Bar Generator With AT90S2313

PAL Colour Bar Generator With AT90S2313

I started this activity 3 weeks ago, because I was apprehensive " is that possible, some AVR MCU to actualize simple colour bars? " At the beginning, I believed that it's easy. So, I asked some bodies who knew added about PAL blended video signal. Some of them told me that it's absurd to aftermath blush absolute in software with an AVR MCU (microcontroller) because there wasn't abundant ability (frequency).

The aboriginal abstraction was to assignment with 8.867238 MHz clear (2 times the blush carrier). When I apprehend added about PAL video blended arresting creation, I saw that if you appetite to artefact colors entire-in-software you charge actualize the color-carrier (4.43 MHz), alteration 4 times the appearance of color-carrier (one time for anniversary color), to appearance 4 colours. Except that, you accept to change the color-burst from 135 deg to 135+90= 225 deg.

So, the 8.86 MHz is not enough, that`s why I acclimated 17.7 MHz clear (4 times the blush carrier). The accessible affair is to actualize the white and the atramentous bar, the blow of this project, beleave me, it's not easy.

The timing (clock cycles) of any apprenticeship is actual important for the phase-shift of the color-carrier and color-burst signals. You should account the cycles afore add or abolish any instruction.

The circuit

The ambit iis constituted by AT90s2313 active at 17.734475 MHz (overclocked) and a , 5-bit DA advocate (R2R-ladder) with 10 resistors.

I know, it's not a acceptable abstraction to overclock 77 % high than the alive abundance of the MCU, but for a few hours, annihilation amiss will happen.

Programm (write) the MCU with colour_bar_gen.hex that it's included in file, affix it on blended video adapter (or scart adapter) of your TV, power-on the ambit and you will see on TV, 6 vertical bars, 4 in color, 1 white and 1 black.

I won't accomplish any account about "how does the PAL video arresting is working" because I will charge a lot of web pages to do that. Maybe some one of you, accept the ability and the time, to abide this project..


Stumble This Fav This With Technorati Add To Digg This Add To Reddit Add To Facebook Add To Yahoo