Tuesday, April 26, 2011

PICAXE microcontrollers

 Day 13

The PICAXE microcontrollers are designed for use in education. They are based on the PIC series of microcontrollers manufactured by Microchip. The PIC chips are generally programmed in Assembly language using the free MPLAB software. This is a useful project to meet the requirements in the grade 12 curriculum but too much of a challenge for Grade 10 students. Programming PIC chips also requires a programming device.


PICAXE adds some proprietary bootstrap code to the PIC chips so that they can be programmed by connecting a cable to the serial port of a computer. (For computers that don't have a serial port, a USB to serial adapter is required.) This provides a low cost method of programming, as no programmer is required. The programming software is free, and it includes a simulator so that students can test their programs before downloading them to a chip. The programming languages include a version of BASIC, and flow charting software that can also generate BASIC code. 

The PICAXE web site is www.rev-ed.co.uk/picaxe

The PICAXE programming editor can be downloaded for free. At the moment the programming editor is available only for Windows PCs, but there is an alternative for MAC and Linux called AXEpad. It lacks some of the functions of the PICAXE programming editor, like the simulator. The PICAXE web site says that the Linux version of the editor is in development. 

When you download the programming editor it includes three manuals. The first has chip diagrams and a series of 10 tutorials that do a good job of introducing students to programming in BASIC for the PICAXE. The second has a complete listing of all the BASIC commands, and the third has several useful interfacing circuits.

PICAXE is a British company, but the best source in Canada is Solarbotics in Alberta. Orders are usually shipped the same day, and the prices are competitive.

Here is an example of a PICAXE circuit:

Robot motor controls using PICAXE 18M

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