Another PFcam teaser

With the help of the new scope, I wrote a new OV6620 driver that includes chroma support. With the camera reconfigured to run at 25fps, it records 88x72 YUV images at full rate. It's 210 bytes, and integrated into a custom build of PropellerForth.

A few lines of Forth later, I had code to generate PPM images. (PPM is possibly the world's easiest format to produce.) Here are some samples. Forgive the yellow cast and the chroma noise -- my new workbench doesn't have lights yet, and the camera's low-lum performance is poor. That, and I probably have bugs in my YUV matrix code.




Once I'm confident in the design, I'll post the driver and Gerbers for the PCB (and if anyone actually wants one, we can go in on a BatchPCB order).

I've got 8 spare Propeller I/O pins...gotta figure out what to do with 'em. Servo connectors? Debug LEDs? Audio?

Edit: Yes, I did indeed have bugs in my matrix code! They're fixed now.

Better chroma makes engineer happy.

I can see clearly now, the waves are gone

I'm a pretty hardcore guy when it comes to debugging software. I pride myself on my automated tests, I routinely sling debuggers and disassemblers around, and so forth.

When it comes to hardware, though, I've been stuck firmly in the printf era. The printf era is pretty damn powerful, of course, when you've got Forth at your side -- the PropellerForth VGA and NTSC display drivers, for example, were written using only a multimeter and ancient HeathKit frequency counter.

However, I'm not a big fan of making my own life difficult. After many years of fondling scopes at Fry's, I finally gave in and picked up a Tektronix TDS1012B. It's at the high-end of the extreme low-end: decent sampling rates for embedded work and so forth.

A couple weekends ago I taught myself printed circuit board and built the PFcam, the Propeller-based image processing board I mentioned in my last post. I'm not an analog electronics whiz, so the first thing I did with my scope was test the new board.

Sure enough -- here's a capture of some I2C traffic between the Propeller and the camera:


Notice the square waves are wearing hats? The regulator's output was bouncing between 3.3v (the goal) and 5v (the input). A decoupling cap later, my SCCB code (Omnivision-speak for I2C) is much more reliable:


Now all the I2C/SCCB chips play nice together, and nobody wigs out and sees a stop condition where there ain't one.

I'm happy with the scope so far. I'll most more details on the PFcam board later on.

Got tired of my CMUcam.

What embedded machine vision system...

• is easier to interface (and more powerful) than a CMUcam2;


• has eight cores at 96MHz, six of which can perform user-defined image processing;


• can be programmed and debugged interactively in-system using Forth or assembler;


• runs open-source code built using open-source tools;


• costs less than $100 in parts; and


• can be built in an evening with only basic through-hole soldering?

Yeah, I couldn't find one either.




Mmm, 192 MIPS of pixel-devouring goodness. I love my overclocked Propellers.

Edit: What kind of image processing, you ask? How about realtime ASCII art!



I hope to get middle-mass and edge tracking working shortly.