Experiment 34: Hardware Meets Software
296 Chapter 5
You can use the PICAXE with a serial cable, but I don’t recommend it. The old RS-
232 serial communications standard on PCs is pretty much obsolete, and PICAXE
has recognized this by offering a USB cable (which contains a serial converter
inside its plug). The USB cable is a little more expensive, but is also simpler and
compatible with Apple computers. From any of the U.S. distributors, buy USB
cable part AXE027, also sold as part PGM-08312 by http://www.sparkfun.com
(quantity: 1). The cable is shown in Figure 5-125.
To write your software and send it down the wire to the chip, the PICAXE
Programming Editor is the tool of choice. It comes in only a Windows ver-
sion. For those who prefer Mac OS or Linux, you can get a free download of
another piece of software known as AXEpad, which has fewer features, but
will do the job. All the downloadable software is freely available from http://
http://www.rev-ed.co.uk/picaxe/software.htm.
Finally, you need a 3.5-mm stereo audio socket with solder connections. The
reason for this is that the manufacturers of the PICAXE have used a stereo au-
dio plug on the free end of their USB cable, and you have to be able to plug
it into something. The PICAXE breadboard adapter, SparkFun stock number
DEV-08331, contains the necessary stereo socket in addition to a few other
little items. Quantity: 1. See Figure 5-126.
Oddly enough, the USB cable is the most expensive item on the list, because
of the electronics hidden inside it.Software Installation and Setup
Now you have to go through a setup procedure. There is no way around this.
Here is what you will be doing:- Install a driver so that your computer will recognize the special USB cable.
- Install the Programming Editor software (or AXEpad for Mac/Linux) so
that your computer will help you to write programs and then download
them into the chip. - Mount the PICAXE on your breadboard and add the socket to receive
downloads.
These steps are explained in the following sections.
The USB driver
Fair warning: If you go to the PICAXE website and try to use its search function,
it probably won’t find what you want. Search for “USB Driver,” for instance, and
it will pretend it has never heard of such a thing.
The PICAXE home page also has irritating drop-down menus that tend to dis-
appear just when you’re about to click on them, but at the time of writing, you
can bypass these issues by going straight to the Software Downloads section
at http://www.rev-ed.co.uk/picaxe/software.htm.Figure 5-125. The USB download cable
made for use with the PICAXE terminates
in a 3.5-mm audio plug. This should not be
inserted in any audio device. It establishes
a serial connection with a computer, allow-
ing program code to be downloaded into
the chip.
Figure 5-126. Closeup of the 3.5-mm stereo
socket that is used with the USB download
cable.