Project : Using a Touch Key Self-locking Switch Module with Exxos RAM Kit

[Marsupilami]

Hello,

I bought this little module in China at sunsky-online.com : A007 Touch Key Key Self-locking Switch Module (~3$ each) .



As I don't like to drill holes in my Atari cases, I would like to use this module as a switch to switch from 1MB to 4MB and ideally place it under the keyboard instead of the existing LED or outside with a simple double-sided scotch.
I found a video on youtube that shows how it works.

That's how mine looks like:

Touch-Key.gif (331.85 KiB) Viewed 3668 times

Obviously there is no documentation at all. So I tested the continuity and voltage between the PINs.
It gives this with the PSU negative 5V connected to GND and the positive connected to VDD:

Multimetre-1.jpg (92.87 KiB) Viewed 3668 times

The question is: Is it possible to use this switch to select 1M or 4M without frying exxos RAM module ? Because i really don't know how to do

[exxos]

It looks like its switching voltages ? If so it won't work, you will kill the MMU at least.

The 3 pads on the MMU board use a spdt switch which switches mad9 in and out of circuit.

[Marsupilami]

It looks like its switching voltages ? If so it won't work, you will kill the MMU at least.

The 3 pads on the MMU board use a spdt switch which switches mad9 in and out of circuit.

Hum ok, but look at the 3 green cells. it seems it just add continuity and no voltage. So maybe it could get 5V somewhere on the board and use one of them ? Or for the others, i was thinking of adding an electronic relay.

[exxos]

continuity to what 0v gnd ? But as said before, this has to be set before the machine is turned on as the MMU maps RAM at power up. I don't know if a cold reset will trigger a re-test of RAM, you would have to try it first.

[Maximilian]

Edit: Oops, read next one

[Maximilian]

Nice touch sensor!

Just a thought:

The cheapest would probably be a an AtTiny to handle when to switch (eg, no switching while the machine is on, or switch and auto reset) and the built in EEprom to hold the state of the switch, and something like an 74LVC1G157 for the switching of the MAD line?
You have to make sure you use wear leveling for the eeprom:
https://sites.google.com/site/dannychou ... -longevity