Originally Posted By: mlord
If we used the spare output from the ethernet chip, then just a pin lift and jumper would be needed, and the rest could be stock and automatic. But then.. anyone who can accomplish the pin lift, could probably handle the existing procedure too.

So.. about that ethernet chip..

The SMC LAN91C96 chip actually has several spare in/out pins. They're not "GPIO", in the sense that they are fixed as either inputs or outputs. But they are there, and unused.

Pins 96,97,99 are IOS0,IOS1,IOS2 --> general purpose TTL input pins, which Patrick was kind enough to factory equip with 10K pull-ups and pads for an unpopulated pin header ("PL9" pins 1-3, plus GND on pin 4).

Pin 3 is also a general purpose TTL input pin, with an internal pull-down (floats to zero on no-connect).

Pins 2,4 are general purpose TTL outputs (capable of 2mA source, or 4mA sink).


I tried fiddling with this stuff today.. it worked fine for automatically repairing the temperature sensor, but..

But.. the ethernet driver performs gratuitous resets of the ethernet chip periodically, including twice at boot. And every time it does this, it messes up the ds1821 temperature sensor.

So, these ouput lines are pretty useless.

Cheers