Dual LED pins

The DS2406 switches arrived from Dalsemi after a long waiting time. Apart from the ability to control the state of two PIO pins, the device includes 1kbit of EEPROM of user programmable memory.

The switch worked straight away when using the DS9097U-E25 serial line adapter and OneWireViewer application supplied by Dallas. But there were problems when I tried to use it with the HA5 adapter - the device wasn't even recognized as being on the network! It turns out that the HA5 is tweaked to drive really large 1-Wire networks: hundreds of devices along long stretches of wire. A notice board-sized Pin&Play surface as the one I was using is a relatively small network in comparison, and this results in an impedance mismatch between the device and the adapter. The DS2406 is particularly suceptible to this problem, which explains why it worked fine with the DS2405 and iButton devices.

To solve this problem, the cable connecting the adapter to the surface was modified with a 150Ohm resisor added in series with the signal line. After this, everything worked perfectly. I imagine that if the HA5 is used to drive much larger, wall-sized surfaces the resistor would not be needed.