VGA Video output on CORTEX-M3.
- This is a revised version of the code which includes orblcd support code.
orblcd allows you to run vidout without a 'real' VGA monitor to test against.
Take a look at at orbcode for more information on
orbuculum in general and orblcd in particular. If you don't want to use
orblcd then comment out
WITH_ORBLCD_MONITOR=1in the makefile...TBH, it will still output to a VGA monitor correctly even with orblcd running in parallel, but that just gets confusing. *
Vidout provides 50 x 18 text output on a STM32F103 CPU (e.g. BluePill) using only 24% of the CPU, 1.2K of RAM and 7K of Flash. It's intended as a development aid and should be trivial to port to other CPUs.
You can see it in action at https://youtu.be/5UFpp3ao460
Pinout;
- PA1 = VSYNC (Pin 14 on VGA connector)
- PA8 = HSYNC (Pin 13 on VGA connector)
- PA7 = Video (Pin 1, 2 or 3 on VGA connector for R, G or B respectively).
Note that the spec calls for VSYNC/HSYNC to be 5V and Video to be 1V max so you might want to put a series resistor on PA7. The input impedence of VGA is 75R so something in the region of 220R should be fine.
To use this subsystem just make sure you've not got anything on the high priority interrupt levels (by default this is configured for the highest two, but the SPI interrupt can have lower priority if you've got other things you need to do).
Just call vidInit to start video output and to get an object back that you can manipulate to create output. Both text and graphic output are supported. See the example main for how to use it, and the API exposed by displayFile too.
In general this should be fire and forget. Once video is up and running it doesn't need any further maintainence or input from you.
Enjoy
DAVE ([email protected])