RGBargy

VGA display library for Arduino and RP2* microcontrollers

This is an Arduino library providing a VGA display-driver for the RP2* family of microcontrollers. The goal of this library is to provide an easy way to drive a relatively low-res vga screen directly from the Arduino framework, and not having to install compilers or the pico development environment.

#include <RGBargy.h>

RGBargy rgbg(RGBG_MODE_640x480);

void setup() {
  randomSeed(analogRead(0));
}

void loop() {
    rgbg.line(
        random(640), random(480), random(640), random(480), random(7)+1
    );
    delay(1);
}

Hardware connections / pinout

RP2040 GPIO pin	VGA connector pin
GPIO 4	Horizontal sync
GPIO 5	Vertical sync
GPIO 6	Red (w/330R)
GPIO 7	Green (w/330R)
GPIO 8	Blue (w/330R)
GND	GND

Supported resolutions

For this library to work, the CPU frequency has to be selected manually in the Arduino IDE to match the resolution used in the code. The CPU frequency must be an integer multiple of the pixel frequencies below. See "CPU freq" column.

Resolution	Refresh rate	Pixel freq	CPU frequency	Clock divider	Status
640x480	60Hz	25.175 MHz	125 MHz	5x	working
800x600	60Hz	40.000 MHz	120 MHz	3x	working
800x600	60Hz	40.000 MHz	200 MHz	5x	maybe?!
800x600	85Hz	56.250 MHz	225 MHz	4x	testing
1024x768	70Hz	75.000 MHz	225 MHz	3x	in the works

VGA timings

The table below shows sync polarity, front porch, sync pulse and back porch lengths for both horizontal and vertical sync lines. For the 640x480 resolution we're actually using a round 25MHz as the pixel clock, instead of 25.175MHz specified in the standard. All monitors we tested seem to tolarate this so far.

Resolution	Refresh rate	Horizontal				Vertical
		polarity	front	sync	back	polarity	front	sync	back
640x480	60Hz	---	16	96	48	---	10	2	33
800x600	60Hz	+++	40	128	88	+++	1	4	23
800x600	85Hz	+++	32	64	152	+++	1	3	27
1024x768	70Hz	---	24	136	144	---	3	6	29

References

Algos

• Midpoint circle algorithm
• Bresenham's line algorithm

Tools / libraries used

• Arduino Pico Core
• Online PIO Assembler

Docs

https://www.raspberrypi.com/documentation/microcontrollers/pico-series.html

License

• MIT license