PS/1 LPX Soft Power Faker
-------------------------
This is a very simple sketch that watches for a switch press from a PS/1 soft
power switch, such as with the PS/1 2155 or compatible platforms. Useful when
the power supply has been replaced with a standard ATX power supply wired as
an AT power supply (either using an adapter or direct wire).

This will probably work with other computers with momentary switches. but has
not been tested with anything other than my PS/1

This should work with most 5V attiny chips and boards but you will need to work
out pin assignments.

on the ML_TINY Board:

PIN 10 -> one leg of the power switch
PIN 09 -> PWR_ON on ATX Supply
PIN +5 -> SDBY_PWR from ATX Supply
PIN GND-> GND from ATX, and the other leg of the switch.

on a bare attiny85/45/25/13

PIN 8 -> SDBY_PWR (+5V)
PIN 7 -> one leg of the power switch
PIN 6 -> PWR_ON on atx Supply
PIN 4 -> GND from ATX, and the other leg of the switch.

if uploading from a eeprom programmer for attiny85 use check the following fuses:
low byte: E2
SUT0=0, cksel3=0, cksel2=0, cksel0=0
high byte: DF
SPIEN=0

leave the rest unchecked (ext. and lock bit should be FF)
  
If after programming you have +5V on pin 7 when applying 5v to
pin 8 and ground to pin 4, the programming was successful.

I recommend cutting the extra legs off splaying the chip out flat and soldering
wires directly to the chips pin, then incase the chip in a 1/2 inch heat
shrink tubing.

see screenshot in attiny85 folder.

Be sure to insulate all your connections with heat shrink and wrap the
controller in kapton tape (or similar to prevent shorts.

it goes without saying program your controller before hooking up, and
do not apply both +5v from the programer and sdby_pwr from the Power
supply at the same time to prevent damage.

the contacts on old momentary switches are prone to getting dirty.
spray some contact cleaner in and exercise the switch if it's being
intermittent.  A very long debounce delay was used to prevent issues.

MIT License:
Copyright 2025 David Collins
Permission is hereby granted, free of charge, to any person
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