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Simple VGA video adapter with ATmega AVR

Simple VGA video adapter with ATmega AVR

This project describes how to create video or vga signal using a 8-bit AVR microcontroller.
With commonly available microcontrollers like the Mega8, Mega16 and similar, and with a minimum of external components I wanted a design that would be capable of displaying at least 15×15 characters on a VGA monitor using standard VGA frequencies. The data itself is to be received by the microcontroller via its USART port. All using a 16 Mhz clock for the AVR.

Initial calculations showed that the the AVR 8-bit microcontroller from ATMEL, with its 16Mhz clock speed providing approximately 16 MIPS was a good candidate for further research. Also note that newer AVRs such as the Mega48, Mega88 and Mega168 will officially support clock rates upto 20 Mhz. Therefore I concluded that with a clock of 16 Mhz I could achieve something in the order of 8 Mhz speed of data being transferred out of a port. I also chose the AVR as I had already built up quite a body of experience with it and so I began work of the project.

After approximately two to three months of research, I present you the fruits of my labour!

Characteristics of the project:

VGA-terminal:



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Quantity of symbols: 20 lines by 20 characters.
The resolution of a character matrix: 8×12 points
Supported code page: WIN 1251
Formed signal: VGA
The resolution: 640×480
Frequency of vertical synchronization: 60Hz
Speed of exchange UART 19200 bps

Video terminal:

Quantity of symbols: 20 lines by 38 characters.
The resolution of an individual character matrix: 8×12 points
Supported code page: WIN 1251
Formed signal: Composite Video (PAL/SECAM)
Resolution: 625 lines (interlaced)
Frequency of vertical synchronization: 50Hz
Speed of exchange UART 19200 bps

Type of the used microcontroller: Mega8, Mega16, Mega32, Mega8535, etc. Clock frequency of the microcontroller standard – 16Mhz.

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