Cheap video solution (VGA & TV)

PatM · Joined: 25 Oct 2004 Posts: 104

I picked up a Parallax Propeller chip and have been experimenting with video output. Amazingly, this chip puts out either VGA or Television signals with ONLY a few resistors and the appropriate connector. I have 320x240x4 colors running right now on my VGA monitor!

The prop is great, and freakin' fast at 80 Mhz, particularly since it is actually 8 processors. My VGA display takes up two processors, leaving six that I can use for other things. No worrying about both driving a display and having enough processing time for your program.

The prop has no built in peripherals like ADCs or PWM drivers but that doesn't really mean much. Between its speed and multiple independent processors, you can add peripheral functionality with code. One fellow already has 12 bit ADC working from a single processor (cog).

There are two main programming schemes for the Prop. First is interpreted basic called Spin. Its compiled to byte code and saved on external eeprom. When the prop starts, the bytecode interpreter is loaded into a cog so it eats up one processor. Second is assembly, if you do not use Spin then you save a cog and ram and greatly speed up execution speed (20-40x). However, the processor is so fast that Spin programming isn't really all that slow.

The achillies heal of the Prop is its lack of memory. Hub memory (shared by all 8 processors) is 32K and each cog has its own 2k ram, but that gets eaten up quickly if you use a video display. 320x240x4 requires 19.2k for the bitmap and then you still have the colour tables etc.

If you aren't interested in video then there's lots of ram to play with.

Personally, I think I'll use mine as a serial display driver and have a Mega chip do the real brain work.

Oh, and they're cheap too. $12 (Can) for a chip and a protoboard from Parallax with chip & crystal is $25.

Wonder if we can convince Mark to port Bascom to the Prop? Basic without the interpreter!

franzachatz · Joined: 03 Jan 2006 Posts: 11

Hi PatM,

i play a lot with BASCOM AVR, but now, i have made a new
Propeller-board with all in.
Check this out:

http://forums.parallax.com/forums/default.aspx?f=25&m=199903

have fun
Franz