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[moved] Multiplexer usage query

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abhishek.2138

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Hello,

I need to interface 14 digital inputs to microcontroller using multiplexer as MCU has less available pins.
Can anybody help how to use attached (datasheet) multiplexer with 8 inputs. I will use two such multiplexers to accomodate 14 inputs.

In the software programm, do I need to toggle the select pins??

Pls let me know.....
 

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KlausST

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Hi,

With this solution you need:
2 data input at the microcontroller (wired to the ´151 "Y" outputs)
3 select output at the microcontroller (wired in parallel to the S0, S1, S2 inputs of the ´151)
(= 5 pins in total)
2 pieces 74HC(T)151

... for sure you need to "toggle" the Select pins. in this way:
* select 000 (bin)
* wait a little time for the signal to settle
* read the input(s)
* select 001 (bin)
* wait...
* read...
* and so on

***

Using a I2C port extender needs just 2 uC pins (SCL, SDA) and has several benefits like: individually selectable input or output, interrupt on pin change, standard interface, software library, ...

Klaus
 

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