HOW COOL IS PERL?

It’s not so long ago that users had to write their own device drivers to add hardware. But with the standardization of USB, and with fully-functional hot-plugging support in kernel 2.6, things have become far easier. The temperature sensor used in this article, a Dallas Semiconductor DS18S20 ([3]), can be controlled via the one-wire bus, which is driven by a USB dongle attached to the computer. The free owfs control software at [2] can request data via a Perl interface. Instead of one-wire, the bus should really be called two-wire, as two thin copper wires (typically in a single sheathing) connect the sensor to the USB dongle (see Figure 1). At the other end there is a western connector (RJ11), which plugs into the USB dongle.