[Alessandro] sent us a link to his post about a PRU software VGA rasterizer. It’s not the easiest read, but we think it’s worth your time.
The gist of his background information is that back when his company was developing for an ARM9 processor he wanted to test his mettle with the coprocessor chips. The first iteration was to write a character LCD driver that pulled data from the main processor’s memory and displayed it on the screen. This makes for a low-overhead debugger display, it’s also very limited (32 characters over two lines doesn’t tell you much). And thus began his work on a VGA generator for the Programmable Realtime Unit (PRU is what TI calls this coprocessor) that grabs data in memory just like the original version. But with a much larger display area this becomes quite useful for debugging. That resistor mess is the R2R ladder he soldered together to perform the Digital to Analog Conversions. There’s a quick demo clip after the jump.
This work could end up being useful to you. [Alessandro] reports that the BeagleBone has similar hardware. A bit of porting could get his generator working on that board as well.