Servo - January 2011

By Fred Eady

Experience the Emperor Pinguino

If the word “Arduino” is foreign to you, odds are that you’ve been exiled to a hole in the ground in the unexplored depths of the Amazon jungle. I recently came face to face with an Arduino while helping some senior aeronautical engineering students complete their senior design project. Not one of the aeronautical-engineers-to-be considered themselves as “programmers.” However, they all adapted to the Arduino environment quite handily.

The Arduino platform the students used intrigued me as I witnessed a bunch of college kids take an unknown entity, learn to use it, and apply it to their control application. I decided to take a serious look into the “Arduino effect.” Arduino is touted as an open source platform and I was pleased to find a couple of Arduino variants that were out of the ordinary. The Arduino variant that caught my eye is really not an Arduino platform at all. It is called Pinguino.

Pinguino 101

I’m not going to get up on my donkey and make the assumption that all of you reading this are intimately familiar with the Arduino environment and the physics that make it work. In that Pinguino is Arduino-compatible, we’re going to concentrate on getting Arduino-like results from Pinguino hardware and software. Currently, Pinguino hardware is based on the PIC18F2550 and PIC18F4550. Pinguino software is very similar to the Arduino and is built from open source packages.

Although the results of AVR-based Arduino designs are for the most part identical to the results one would expect to receive from a Pinguino design, the Pinguino hardware is very different in content. A typical piece of AVR-based Arduino hardware is based on an Atmel ATMega8, ATMega168, or ATMega328. Larger AVR microcontrollers are also being integrated into the Arduino environment. As of this writing, the flagship Arduino board is the Uno which is based on the ATmega328. The new Arduino Uno differs from its ancestors in that the FTDI USB-to-UART IC has been replaced with an ATmega8U2 USB-enabled microcontroller.

The advantages of using an AVR instead of the FTDI part are speed and USB class flexibility. The new Arduino platforms that are front-ended with a USB-equipped microcontroller can be configured as HID-class USB devices, as well as CDC-class devices.

You can beat the AVR and PIC datasheets against each other to pull out the fine points of differences in the microcontrollers. However, in a nutshell, the Pinguino platform is based on a USB-enabled PIC and does not require an additional USB front-end device. The PIC18F2550 is a 28-pin USB-enabled PIC and offers up to 18 I/O pins that fall under the control of the Pinguino environment. The PIC18F4550 is available in 40-pin DIP and 44-pin TQFP packages and — if you include the RUN LED I/O pin — brings 30 I/O pins to the Pinguino party.

The Pinguino environment is designed to operate with the same C-type mnemonics used in the Arduino programming environment. That makes sense as the Arduino and Pinguino are both based on open source code. Both the Arduino and Pinguino platforms leverage open source to allow them to run on all of the popular operating systems which include Linux, MAC OSX, and Windows XP/7.

As I alluded to earlier, the Pinguino programming language is very similar to C. However, there is no C main function. The C main function is replaced by a loop function. A setup function is also part of the Pinguino programming model. The setup function runs only once following a hardware or power-on reset. Here’s a super simple example of how the setup and loop functions are used to blink an LED attached to one of the Pinguino microcontroller’s I/O pins: