How to control a demultiplexer

[ericgibbs]

So are you saying pin 1 is a direction control pin? So for in to out pin 1 should be low right?

No its not a direction pin.

Imagine the ic as being 16 mechanical switches with one side/pole of all the switches linked,,, thats the 'Z' pin.


The address lines are 4, so only one switch can be ON at any one time.


EDIT:
Being 'a mechanical' analog it means is switches Z, to either selected pin 0 thru 15 i/o's are b-directional

 

[Mikebits]

Slap me silly and call me suzy, dang, I been looking at it all backwards. So it is a 1 to many, not many to 1. Pin 1 is input or output, now I got it, I think.
I must be going lulu...

 

[Mikebits]

Sorry overgift, Did not mean to mislead you

 

[ericgibbs]

Slap me silly and call me suzy, dang, I been looking at it all backwards. So it is a 1 to many, not many to 1. Pin 1 is input or output, now I got it, I think.
I must be going lulu...

Its either as its analog.

1 input to one of 16 outputs OR one of 16 inputs to 1 output..

 

[Mikebits]

Got it Eric, thanks for the enlightenment So I assume OP is using as a 16 to 1, is that your assumption as well?

 

[Mikebits]

The demux is HCC 4067B.

The uC to demux is simply. A;B,C,D, INHBIT are the control bits of demux.

connection is:

p2.0-->A
p2.1-->B
p2.3-->C
p2.4-->D
p2.5-->INHBIT

the other pins of demux are output channels. Vcc is 12v.

So maybe we have 1 to 16? A drawing would really help as your not explaining your setup very clearly.

 

[overgift]

I havnt seen your program.

If you suspect the 4067, I would disconnect the 4 address wires from the MCU.

Connect the 4 address pins to 0V and +V to make different addresses, monitor the Z pin of the 4067..with a scope

Is it audio you are trying to select, if so, how is the signal connected to the 4067.?

I use an voltage source as a selected signal. Therefore when I change the input voltage, I hope to see the same change in the selected channel. The plus of the voltage source is connected to the Z pin, the minus is connected to the Ground of demux.

 

[ericgibbs]

I use an voltage source as a selected signal. Therefore when I change the input voltage, I hope to see the same change in the selected channel. The plus of the voltage source is connected to the Z pin, the minus is connected to the Ground of demux.

Thats the way I use the 4067, Im suprised that you are having a problem.

What sort of voltage levels are they.?? mVolts or volts,?

Whats the Z output connected to.?

 

[overgift]

Hi all,

At the beginning of the test, I gave a 0000 to the demux, therefore the 0 channel was chosen, and it worked totally fine, and now seems the signal has been locked in the 0 channel, It cannot switch to the other channels, no matter how I modify my code.

 

[overgift]

Thats the way I use the 4067, Im suprised that you are having a problem.

What sort of voltage levels are they.?? mVolts or volts,?

Whats the Z output connected to.?

Now the output channels are leaved free, later they will be connected to PZT sensors. Now I just wanna debug the switch function.

 

[ericgibbs]

Now the output channels are leaved free, later they will be connected to PZT sensors. Now I just wanna debug the switch function.

OK,
I assume that you are running the MCU and the 4067 at 5V, power and select lines, and that the Enable is being switched to 0V

 

[overgift]

The voltage signal level is volts...since HCC4067 can handle voltage level as high as 15v.

 

[overgift]

OK,
I assume that you are running the MCU and the 4067 at 5V, power and select lines, and that the Enable is being switched to 0V

Im running the MCU and 4067 at 12v.

 

[ericgibbs]

Im running the MCU and 4067 at 12v.

Thats OK, within the +15V max.

Using a scope or dvm are the mcu to 4067 address lines changing levels, from about 0.3V upto about +11V... and whats the Enable pin voltage.


As its a CMOS ic. its possible its died, if its been damaged with esd.

Are you observing ESD protection while handling the 4067 devices.?

 

[overgift]

Thats OK, within the +15V max.

Using a scope or dvm are the mcu to 4067 address lines changing levels, from about 0.3V upto about +11V... and whats the Enable pin voltage.


As its a CMOS ic. its possible its died, if its been damaged with esd.

Are you observing ESD protection while handling the 4067 devices.?

What do u mean observing ESD protection?

 

[ericgibbs]

What do u mean observing ESD protection?

Well ESD electro static discharge can easily damage CMOS ic's.

For example if you are charged statically due to walking on a carpet say, if you pick touch the CMOS pins, you can discharge yourself into the ic.

You should wear a earthing wrist strap while handling CMOS, also earth your solder iron.

Do you follow.?

 

[overgift]

Well ESD electro static discharge can easily damage CMOS ic's.

For example if you are charged statically due to walking on a carpet say, if you pick touch the CMOS pins, you can discharge yourself into the ic.

You should wear a earthing wrist strap while handling CMOS, also earth your solder iron.

Do you follow.?

aha.. ESD protection I know, I ground myself with touching the ground of the wall plug. I thought u meant observing it by some way.

u know weird thing is if I damaged the chip, then a new chip should work properly, but after changing another same demux, the channel 0 was still locked.

 

[ericgibbs]

aha.. ESD protection I know, I ground myself with touching the ground of the wall plug. I thought u meant observing it by some way.

u know weird thing is if I damaged the chip, then a new chip should work properly, but after changing another same demux, the channel 0 was still locked.

Did you measure the MCU to 4067 pins as I suggested to confirm that they switching and are the correct voltage levels.???

 

[overgift]

Did you measure the MCU to 4067 pins as I suggested to confirm that they switching and are the correct voltage levels.???

YES, I measured them, the i/o pins of uC, and the ABCD pins of demux, they are all fine. If I change the control code, they change respectively...

 

[ericgibbs]

YES, I measured them, the i/o pins of uC, and the ABCD pins of demux, they are all fine. If I change the control code, they change respectively...

Thats a little strange.

Where are you located.?