Update: Added KiCad fabrication files for a T4.1 VGA adaptor board. They can be found in the Extras folder.
Schematic for RGBI R2R VGA ladder can be found at the begining of VGA_4bit_T4.cpp file.
This is a 4 bit per pixel VGA driver using FlexIO2VGA. There are three main files:
- VGA_4bit_T4.cpp
- VGA_4bit_T4.h
- VGA_4bit_Config.h
I wanted to optimize memory usage so at this time I am not using double buffering although it is available. The hard part was learning to pack and unpack two pixels in one byte. Once that was figured out it was fairly easy to build on it. Thanks for the help jmarsh...
There are four supported video modes:
- 1024x768x60
- 800x600x60
- 640x480x60
- 640x400x70
Since this version of the driver is using DMA memory DMA and malloc memory are affected by the screen size.
Each nibble (one pixel) can be one of 16 RGBI colors (0 to 15):
- 0 VGA_BLACK
- 1 VGA_BLUE
- 2 VGA_GREEN
- 3 VGA_CYAN
- 4 VGA_RED
- 5 VGA_MAGENTA
- 6 VGA_YELLOW
- 7 VGA_WHITE
- 8 VGA_GREY
- 9 VGA_BRIGHT_BLUE
- 10 VGA_BRIGHT_GREEN
- 11 VGA_BRIGHT_CYAN
- 12 VGA_BRIGHT_RED
- 13 VGA_BRIGHT_MAGENTA
- 14 VGA_BRIGHT_YELLOW
- 15 VGA_BRIGHT_WHITE
There a few examples of usage including a graphic cursor as well as a simple screen editor using an adapted version of the Kilo editor found online here: https://viewsourcecode.org/snaptoken/kilo/.
Examples:
- VGA_T4_Editor -- Requires a USB keyboard plugged into the T4.1 USB host connector. The Kilo editor supports most common editor keys, simple syntax highlighting of C/CPP/BAS files, simple searching and horizontal scrolling of long lines. This sketch uses built in SD card reader and optionally a USB drive if using a USB hub. Uncomment "#define USE_USB_DRIVE 1" at begining of sketch to use USB drive. F1 key for help.
- VGA_T4_Gauges -- This is a version of Sumotoy's gauges sketch found in his RA8875 library.
- VGA_T4_GraphicCursor -- An example of a software driven graphic cursor. Requires a USB mouse connected to the T4.1 USB host connector. There are four types of graphic cursors available (Block, Filled Arrow, Hollow Arrow and I-beam). This uses the "drawBitmap()" function to render the cursor. More could be added. Uses 8x16 bitmap.
- Grahics -- Demonstrates some of the graphic primitives like drawing circles, filled circles, triangles, filled triangles, rectangles, filled rectangles, ellipses and filled ellipses. Filled ellipses have a problem with filling out of bounds with certain parameter combinations have not figured out why yet. Example of fail: fillEllipse(516, 419,59,61,VGA_BRIGHT_WHITE). Resolution does not matter.
- VGA_T4_Mandelbrot -- A uVGA example adapted to VGA_4BIT_T4. Finally drawing text in four different directions.
- VGA_T4_treeDee -- Another Sumotoy example showing a rotating 3D framed cube.
- VGA_T4_Box_Test -- Demonstrates allocating memory for saving and recalling sections of video memory.
- VGA_T4_Windows_Test -- A very simple windowing system.
All files are heavily commented.