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Topic: is reverse Multiplexing possible? (Read 14890 times) previous topic - next topic

Grumpy_Mike

At this stage you need a block diagram of your concept. As Paul says that circuit simply does nothing.

Draw the multiplexers as physical switches.

sonnystikz



I'm sorry but I still don't get the concept. Your diagram just looks like a hilarious way to waste multiplexer chips to me. The pot could just be fed directly to the Arduino. Perhaps a diagram that demonstrated how it would work with 4 pots and 4 banks would better demonstrate your idea. But not with that diagram app, needs to be something more suitable, even a sharp pencil and squared paper would be preferable. Have you thought of trying Eagle or Fritzing?

Paul



I use NI Multisim- resolution is very low from the screen print tho-  ill take another stab at it later

steinie44

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rushed thru it- so i hope you enjoy the art-  but this is a very watered down basic concept of what i want to

* pretty Sch sample.jpg (242.58 KB, 1000x366 - viewed 7 times.)

This will do just what I said in reply 24. Only 1 line to 8 then 8 lines to 1.
Your select lines are all common to both ICs from D1 to D4, so there is only one result. Pot 1 to A0.


PaulRB


This will do just what I said in reply 24.


Yep, and what I said in reply 7. Glad I'm not the only one who just doesn't get it!

steinie44

Is something like this: http://www.musicfromouterspace.com/index.php?CATPARTNO=&PROJARG=SEQUENCER_VARICLOCK%2FSEQUENCER_VARICLOCK.php&MAINTAB=SYNTHDIY&SONGID=NONE&VPW=1430&VPH=674 is what you are building? If not, please find something like you want, on google or whatever, and post it. So we can get a idea of what the final project will do.

Grumpy_Mike

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use NI Multisim- resolution is very low from the screen print tho-  ill take another stab at it later

We are not interested at this stage in things like the power to the chips or the individual select lines. What we want to knw is what on earth you are on about.

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Glad I'm not the only one who just doesn't get it!

I think no one knows what you mean and what you hope it will achieve. Your description is very abstract and muddled sounding.

Maybe it will help if you describe the over all project and what it is trying to do.

sonnystikz

#36
Jul 30, 2014, 10:50 pm Last Edit: Jul 30, 2014, 10:58 pm by sonnystikz Reason: 1
ok- My main question was is it possible...... I'm pretty sure it is after all of these comments to go 1 to 16- then 16 to 1 as what was said in reply #24


but to give you all a more in depth idea of what i need it for.......

A midi Mixer with 99+ assignable  Channels-  each Channel  has to control 8 effect knobs, 9 Eq Knobs, 1 Pan Knob, 1 Stereo Width Knob, and 1 Volume Slide/ fader

all together that is 1980, total controls-  I'm aware of the extravagance and some of the limits,

So the concept is to take about 10 physical channels- each with 4 Eq knobs, 3 eq knobs, a pan knob, a stereo knob and a volume fader.  the 10 physical channels will represent a bank group,  each Channel will consist of 10 Virtual banks-  

I dont need the channels to switch individually- more so the entire bank group--  1-10, 11-20, 21-30....etc

the Eq and Effect knobs will break down into "sub groups"- to access the additional virtual controls per channel since there are only 4 effect buttons per channel- i'll need to switch to the second set of controls within each bank group.

overall i'm not sure how possible this is exactly, or if i may need to daisy chain more micro controllers- but the reason why i'm creating it is partially based on the overall challenge and learning aspect

the cost for parts isn't a major issue- I'm more concerned with the overall size of the finished unit

The problem i see with multiplexers is they need to be told when to switch channels-  all the controls on the board have to be active at any time, so muxing them won't work.... I don't want to press a button for the Effect knobs to work....etc

De- multiplexing each pot will use too many Analog Pins.  - so i figured i need to de-mux without alot of analog pins- makes sense to mux the de-muxed signal

Grumpy_Mike

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My main question was is it possible

Yes it is possible.
But for your example it doesn't seem to be necessary.

You just want to multiplex, and just do 10 pots at a time rather than individually.

It is just a matter of arranging your banks.

You don't even need to switch these you just need to read them into different values of an array to use them for the appropriate channel.

This is why we are all puzzled, what you are asking simply doesn't make any sense.

sonnystikz


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My main question was is it possible

Yes it is possible.
But for your example it doesn't seem to be necessary.

You just want to multiplex, and just do 10 pots at a time rather than individually.

It is just a matter of arranging your banks.

You don't even need to switch these you just need to read them into different values of an array to use them for the appropriate channel.

This is why we are all puzzled, what you are asking simply doesn't make any sense.




100 pots at a time  not 10


4 effects, 3 EQ, 1 stereo, 1 pan, 1 volume  x 10 = 100

sonnystikz

I'll read up more on the array tho-  you all know alot more about the coding than me obviously- so i'll see how i can apply it

Grumpy_Mike

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100 pots at a time  not 10

Yes but you don't actually want 100 pots or do you?

Lets say for the moment you only need 6 pots per bank you could read in a bank with no multiplexing on a Uno.

1) If you wanted 8 of these banks using real pots then you would switch each bank over by use of a 4051 on each of the 6 analogue inputs. This is conventional multiplexing.

However:-
2) If you wanted to have only one set of real pots and use them to control 8 'things' then you would not need any multiplexing at all. You would simply read in all the analogue inputs and apply them to the 'thing' you currently want to control. You can have a multi position switch just wired to digital inputs to determine what 'thing' you are currently controlling. You would need no multiplexing chips at all.

Either way there is no need for 'reverse multiplexing' as you call it. It is either multiplexing or no multiplexing depending on which one of the two situations outlined above you want to do.

sonnystikz


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100 pots at a time  not 10

Yes but you don't actually want 100 pots or do you?

Lets say for the moment you only need 6 pots per bank you could read in a bank with no multiplexing on a Uno.

1) If you wanted 8 of these banks using real pots then you would switch each bank over by use of a 4051 on each of the 6 analogue inputs. This is conventional multiplexing.

However:-
2) If you wanted to have only one set of real pots and use them to control 8 'things' then you would not need any multiplexing at all. You would simply read in all the analogue inputs and apply them to the 'thing' you currently want to control. You can have a multi position switch just wired to digital inputs to determine what 'thing' you are currently controlling. You would need no multiplexing chips at all.

Either way there is no need for 'reverse multiplexing' as you call it. It is either multiplexing or no multiplexing depending on which one of the two situations outlined above you want to do.


perfect explantation- thats what i need- and yes i need 100 actual pots  for 100 different parameters to be accessed at any moment

with banks to control a few thousand parameters total- but sounds like the array is the code  version of what i was trying to do with the multiplexers

Grumpy_Mike

Ok, do you realise the snag with this?
Appart from having to poll the pots to see if any have moved when you apply one bank of physical pots to one mixer channel and then switch it to another mixer channel the new channel will acquire the value from the first channel as soon as a knob is touched. For example your pots are all on quite on one channel and you switch to a channel that previously you set at high then as soon as you touch a knob it will drop down to that quite level.

To prevent this you have to use incremental shaft encoders so you do not read absoloute values from a control but only changes.

sonnystikz


Ok, do you realise the snag with this?
Appart from having to poll the pots to see if any have moved when you apply one bank of physical pots to one mixer channel and then switch it to another mixer channel the new channel will acquire the value from the first channel as soon as a knob is touched. For example your pots are all on quite on one channel and you switch to a channel that previously you set at high then as soon as you touch a knob it will drop down to that quite level.

To prevent this you have to use incremental shaft encoders so you do not read absolute values from a control but only changes.


i thought about that issue- how exactly would that work? with the incremental values? 

Grumpy_Mike

Yes you increment the values from last time.
The point is that you loose any positional information the knob's position gives you and that is more than important than you think .

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