Gadget Gangster Propeller Platform - Review
April 3, 2010
The Propeller from Parallax is a pretty neat processor. 32 I/O, up to 80Mhz clock speed giving 160 MIPS, available in a DIP package. But best of all it can actually multitask and do as many as eight things at a time. Until recently, though, there hasn't been a really easy-to-use prototyping board for the Prop. Yes, Parallax has modules that plug straight into a breadboard, but that doesn't make for the cleanest of robot projects. And yes, there are some Propeller boards that have a large prototyping area. Once you've soldered up your circuits on one of those there isn't a whole lot of reusability anymore. Despite being available for several years there just wasn't, to the best of my knowledge, a simple, flexible, plug-n-play type of single-board microcontroller based on the Propeller.
Finally Gadget Gangster stepped up to the plate and brought us the Propeller Platform Module. Similar to the Arduino in layout, the Prop Platform is almost everything you need to get started using the Propeller chip in whatever microcontrolled project you've got in mind. Add to that a selection of pluggable, stackable modules and the Prop Platform is just as ready to be a video game system as it is a motor controller.
On the power end you have a plain old 2mm barrel jack to plug in your favorite wall wart. If you prefer screw terminals that's an option too, GG has put the appropriate holes in place. Just solder one on instead of the barrel jack. Past the switch there are two regulators supplying both 3.3V and 5V, and three 47μF capacitors to make sure things are nice and smooth. Three indicator LEDs to let you know what has juice and what doesn't.
The other end of the board has the brains of the operation, the Propeller chip itself (complete with a handy sticker to know just which pin is which) . Next to that is a socketed 5MHz crystal and a 4.7μF tantalum capacitor. The larger cap and the socket make the Prop Platform really brainless to overclock as well. Just pull the 5MHz crystal out and stick a 6.25MHz crystal in its place and it bumps up to 100MHz (200 MIPS). The little chip on the top-right is a 32KB EEPROM for storing your code. just below that is another 8-pin footprint for adding a second EEPROM if you need some space to store data. Both of these are tied to P28-P29 for I2C communication. At the bottom is a standard reset tact switch, and the 4 pin header for the Prop Plug or USBThumb programmers.
The whole thing comes in at 3.8" x 2.5" (96.5mm x 63.5mm). That's a 40 pin header above the board for some reference. As you can see in the photos, all 32 I/O, plus VIN, GND, 3.3V, and 5V are brought out to holes on .100" centers. Since the Prop Platform comes in kit form you can have your choice of male or female headers, both, or none if you prefer. There are also two rows of header holes so you can put the two different headers on both sides of the board for easy module stackability.
As the name suggests, the Platform Prototyper Module is designed to give an area to build whatever you want and plug it onto (or beneath) your Prop Platform. The top 1/3 or so is a series of unconnected through holes (point-to-point), with an 8-pin SOIC footprint for playing with surface mount chips. The bottom 2/3 has various connected holes giving at least 2 empty pins for each of the I/O from the Propeller chip, and 4 rows for power/ground busses, or whatever you like. This is the module I used for connecting an h-bridge, servo, and PING))) sensor to the Prop Platform in the 812-R8 robot.
All in all the Propeller Platform seems to be a really handy way to start playing with the Propeller chip. It manages to take all the good parts of the Arduino platform, kills some of the annoying parts (like the goofy 1.6 hole header spacing), and stuffs a hot rod chip into the mix too. With the growing selection of plugin modules adding features to your project is easy (who'll be the first to build an El Jugador robot?). And since the PCB measurements match ExpressPCB's miniboard service, making custom modules with professional quality PCBs can be simple and fairly inexpensive. As if that weren't enough, the Propeller Platform will also be featured in the Spin Zone column of Nuts and Volts Magazine for even more tips and project ideas. Finally, if soldering, or a USB programmable board aren't quite your cup of tea, be sure to check the Propeller Platform SD which comes mostly prebuilt and lets you run your code straight from a micro SD card.
I leave you now with a few more photos. Please feel free to leave any comments or questions, as long as they're not about my soldering skillz ;)