On 07/12/2013 09:45 AM, Craig R. Skinner wrote:
I've a box that won't self start after a power failure.
The BIOS docs shows:
Remote Ring On
This allows you to wake up the system from a serial port modem.
How could this be done from another OpenBSD box connected via a serial
cross over cable + cu/tip/etc?
The serial link is operational & I get the console on the
non-self-starting box after I manually press the power button.
Thoughts?
not going to give you a "do this and all will work", but I'll tell you
how to figure it out.
1) verify that this "feature" really works on this machine...
a) Get a nine volt battery and a battery clip ending in two wires.
b) Connect the battery between the Ring Indicator (RI) pin and the
ground pin.
c) If it doesn't turn on, swap the red and black wires, and try again.
d) If it still doesn't work, it's a left over feature in the bios,
your hardware doesn't actually support this.
2) Find a line you can control on the terminal machine. man 4 tty,
man 4 termios appear to be useful.
a) Get/build an RS232 monitoring plug, and figure out what RS232
handshake line you can control (std two-pin, red/green LEDs and 1K
resistors do just fine here)
b) the pin you can control should default to the right polarity for
what you wish to accomplish.
3) Make it work
Build a custom cable which connects the line you can control to the
ring detect line.
Note that standard null modem cables don't generally pass the RI pin, so
you will be building one.
Maybe easier: just strap the RI pin to a level that causes the machine
to light up on its own. An old cell phone charger or other wall wart
may be usable to do this.
A stupidly simple trick to make a box auto-start after a power failure,
and I think I can credit Henning@ with suggesting it to me, is to put a
capacitor across the power button lines. On power-up, the capacitor is
discharged, so passes current, acting like someone was pushing the power
button. It quickly charges up, and now it acts as if someone released
the button. IIRC, 100uF worked pretty well on one machine I did this
with, your results will vary. Make sure you get the cap polarity right,
or it won't last very long!!
I found it good to put a bleeder resistor across the cap/switch combo,
too, as otherwise the power had to be off too long to auto-start when it
came back up (the capacitor was still charged!), you will have to
experiment with this. The bleeder resistor should be as low in
resistance as doesn't cause the machine to think the button is pushed,
maybe try 1k, 10k, 100k, 1M values.
Nick.
