Nuts and Volts - September 2011

■ FIGURE 7

Download the project code (which bundles everything discussed here into a reusable object) and have a look at the rest. You'll see that I've also added methods to set the position and move the speed of all the servos with a single call. Another method allows us to wait until a specific servo channel reaches its intended target.

For me, anyway, this is just a start. Having the ability to create servo pulses with 1 µS resolution and enough time between servo pulses to add speed control features using high level code (Spin) means that the Propeller is likely to become a very serious player in the servo control arena — especially for those projects that have available I/O. For those of you that don't want to roll your own hardware but would like a custom servo controller, you can always get a Propeller PSC from Parallax and reprogram it. With the code we've developed here, you're well on your way. Here's a hint for controlling the other eight outputs on the PPSC: Each cog has two counters. Use the second counter to generate pulses for the second set of eight outputs. This keeps the servo pulse generation in a single cog.

Arduino. It's understandable.

The marketing machine behind the Arduino is doing a great job, and I designed the Propeller platform to be stackable like the Arduino.

When I told him about the Propeller, he was interested but not enough to give up his investment in Arduino "shields." Well, good news: You can use those shields with the Propeller — the Propeller ASC (Arduino Shield Compatible) from MGH Designs, that is. As you'd expect, the Propeller ASC is a small board, the same size and layout (including the odd header spacing) as a traditional Arduino. An on-board ADC handles the analog input pins.

I have nothing against the Arduino but having worked with one, I find the Propeller easier to program and far more powerful. If you're an Arduino user that's been wanting to give the Propeller a go, now you can. I'm pretty certain you'll be happy for doing it.

Until next time, keep spinning and winning with the Propeller! NV

GOOD NEWS FOR ARDUINO FANS

While working on a lighting project in a Hollywood prop shop, I was approached by a member of the crew who asked if the Propeller platform I was using was an