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PICAXE Goes Wireless , Pt 2

Networking. logging data, plus light & temperature sensors

by Clive Seager

In PART 1 last month, we described how to build and test a
pair of wireless data communications nodes based on AXE210 project boards and XBee modules from MaxStream. This month, we look at some of the more advanced features of the XBee modules.

By way of example, we then learn about some of these features during the construction of a wireless light and temperature sensor, based on one of the AXE210 boards. As part of the project, we also see how to receive and log the data from the wireless sensor to disk with the aid of the second AXE210 board and a PC.

Finally, we dispense with the PC altogether and see how easy it is to get a PICAXE-to-PICAXE wireless link up and running!

XBee networking

Click for larger image
Fig.1: here's a screen shot of the XBee Setup wizard, showing the correct settings for board #1. Remember to swap the DL and MY values around when programming board #2!

As demonstrated last month, sending and receiving data between two XBee modules is quite straightforward. In those examples, we relied on the XBee’s default settings.

However, consider the case where more than one module is within receiving range. Unless we specifically want to send a "broadcast" message to all modules, then some means of addressing the data to the intended recipient is required.

This is where the XBee’s intelligent networking features come into play. For a start, each module is factory programmed with a unique serial number, allowing it to be explicitly addressed. In addition, each XBee module can be identified with a programmable "nickname" for ease of use.

Other powerful networking features include the ability to arrange modules into groups, or "private area networks" (PANs). By assigning a common group ID to all members, modules not part of that group are automatically excluded.

So how do you set an XBee module’s nickname or group ID? Well for modules connected to a PC, it’s quite straightforward; you’d use the Programming Editor’s "XBee Setup" wizard. We’ll investigate this method in more detail shortly.

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