I'm sure many of you out there have had the idea to produce a fairly simple PIC project until you have discovered the complexity of hand writing code, debuging and producing the finished hardware. An alternative would be to purchase a basic or 'C' compiler to ease the software development phase.

The PICAXE range of processors were developed in the United Kingdom (with Oil & Gas funding) by Bath firm Revolution Education Ltd. These preprogrammed, interpreter devices are extremely cheap and only have a few limitations.

All PICAXE processors are programmed using a language which is a variant of BASIC. The software to do this is available for free (the download is around 16MB in size). Make sure you download the latest version which now includes a 4 channel data plotter! The Programming Editor is Windows compatible only software, running on 95, 98, ME, NT, 2000 and XP, and supports not just PICAXE programming, but also Basic Stamp programming, native PIC Assembly Language programming, and has the ability to program blank PIC chips. Apart from the BASIC commands, the Programming Editor allows programs to be entered as flowcharts. The Editor also permits you to simulate how your program will operate, a great time saving feature.

The product is mainly aimed for schools but allows seasoned constructors to produce working projects quickly. All software is free and available on the WEB and many active forums and user groups can be found on the WEB. The only downside is that the devices although standard Microchip flash PIC's are preprogrammed with what is called a bootstrap loader by Revoloution which means they are single sourced component and possibly no suitable for industrial production. Each chip does carry a royalty overhead for the loaded software but is probably cheaper than buying the PIC in small quantities from the major UK suppliersThis is the Kit I started out with. For approx. £25 it contains all you need to get your projects up and running. There are cheaper kits available if you wish to add your own driver hardware but this unit comes complete with software, PICAXE chip, comms cable, battery pack etc. On board hardware includes seven segment LED display, Light dependent resistor (LDR) and push buttons. Once the code has been developed I normally rebuild the hardware on stripboard or veroboard.

Click here to see my PICAXE driven robot

No programmer or UV eraser is required for these 'flash'memory devices, software is downloaded via the serial cable provided. The program is written in BASIC then downloaded to the board. One feature I found particularly useful was a debug command which allows all registers to be displayed on a debug window on the PC whilst the program is running.

Commands are present within the BASIC system for the following :-

Model Servo control.
Serial driver commands.
PWM for variable speed motor drive
Analogue to Digital conversion
Temperature monitoring
Sounds including the ability to reproduce monophonic ring tones downloaded from the WEB.

Please note there are a range of PICAXE processors, not all functions work on every one. Click here for the BASIC Manual.

The picture above shows how the final project can be constructed on Veroboard (stripboard). The starter boards from Revolution Education Ltd. tend not to be 'mountable' friendly so I have rebuilt it to suit my target hardware. I have included the serial programming port on the board so new versions of the software can be downloaded without the need to remove the processor from the board each time. The project interfaces a PIXAXE to a SPO256 speech synthesizer. Although these chips became obsolete many years ago they are still readily available either on Ebay or new from various suppliers.

Another example of how the 8 pin PICAXE can be pressed into action. Here I am experimenting driving a 5g miniature servo recently purchase off ebay. I understand up to eight servos can be driven independently from one PICAXE. As we are using the 08M device we hopefully will be able to drive three in order to produce a hexapod robot. I will keep you informed of it's progress.

Here we see how easy it is to interface with a display Four wires connect the serial module up to the starter board. The LCD assembly can interface through a normal serial connection or I2C which is a standard protocol used in televisions for Teletext chips etc. The LCD display module costs about £14 and has the option of fitting a real time clock so you can display the time and date on your projects.

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