help with multiplexing/demultiplexing

[dataplex]

dear list,

i have just finished making a touch sensitive keyboard, where each of the touch nodes output 5v logic as you touch them.

i need these signals to be sent to another module through a cable, to turn things on/off - so rather than using a bulky 30 wire cable to get the control signals where i need them, i thought the 4067 multiplex breakout from sparkfun might come handy :: https://www.sparkfun.com/products/9056

i understand this mux chip can also serve as a demultiplexer, however i dont quite understand how to pack the button states into a single datastream on the keyboard side, and how to unpack them on the other.

would i be able to use another 4067 chip in reverse? or do i need an arduino to scan through the inputs at high speeds?

here is a diagram of what i need to do:

any thoughts would be greatly appreciated!!
thank you so much

all the best,
-úlfur

 

[dr pepper]

The multiplexer might do the trick, you would also need to send sync signals down the transmission line as you need to keep the demiltiplexer in sync, the demultiplexer chip is probably limited in how much current it can switch.

You mentioned an arduino, this is a much better idea, encode the keys then transmit in rs232 or similar protocol to another arduino that drives the loads.
With serial comms its possible to do this with just 2 wires if both ends have power.

 

[Nigel Goodwin]

Yes, using a processor is a much better idea - and much more versatile - as Dr. Pepper suggests, just send it as RS232.

Perhaps a bit late now?, but processors can often do the touch keypads directly as well, giving a single chip solution.

 

[cowboybob]

The single wire serial requirement considerably increases the complexity and cost. For single wire serial you'll need two uCs (with at least 16 I/Os and, of course, the necessary code for both).

If you're willing to use a shielded 4 wire cable (standard indoor telephone cable, for instance, shield as ground) you could use one Sparkfun 9056 to mux the touch screen signals, xmit the binary output (s0 -> s3) to another 9056 (in reverse) to demux for the 16 control function(s) you want.

No doubt some manner of current handling circuit(s) would be needed at the output end.

 

[canadaelk]

Or the old-fashioned DTMF encoder/decoder (MK5087/MK5103 with a 4514). But that could be to simple! E

 

[magvitron]

IHO, RS 485 will be much better for noise environments such as home.

 

[prprog]

dear list,

i have just finished making a touch sensitive keyboard, where each of the touch nodes output 5v logic as you touch them.,....

Can you share the schematic of the touch sensitive keyboard ? I do electronic apply to musical instrument and such keyboard sound interesting.
Thanks,
PRPROG

 

[dr pepper]

This might be more your kind of thing prprog.

https://people.ece.cornell.edu/land...9_kre27_stj26/as2799_kre27_stj26/website.html

 

[Nigel Goodwin]

Can you share the schematic of the touch sensitive keyboard ? I do electronic apply to musical instrument and such keyboard sound interesting.
Thanks,
PRPROG

Here's a link I've posted a number of time, it seriously impresses me

http://www.pic24.ru/doku.php/en/osa/articles/pk2_osa_piano

 

[prprog]

This might be more your kind of thing prprog.

https://people.ece.cornell.edu/land...9_kre27_stj26/as2799_kre27_stj26/website.html

Thanks Dr. Pepper for the link.

 

[dr pepper]

Nice one Nige an electronics guy that can play tocatta, thats a first.

 

[Nigel Goodwin]

Nice one Nige an electronics guy that can play tocatta, thats a first.

My little brother can play it - but I think it's all he can play

Mind you, he's a 'banker' - or was, works for Visa now.