Pin to gnd in place of digitalwrite(LOW)?

Other Hardware General Electronics
1

I am still pretty new to this area, but really enjoying playing with the Arduino’s and learning a lot thanks to forums like this. Typical “this is a very n00b question” disclaimer here.

I am using a Nodemcu ESP8266 12-e which only has one analog pin. I am trying to read two analog sensors so I got a CD4051 multiplexer https://a.co/d/0i9eqXN

Since I am not planning to read more than 2 analogs, I never plan to toggle the B and C bits to read analogs beyond pins 0 and 1.

I am low on digital pins and would like to avoid wasting 2 to write LOW to pins B and C.

Silly question: can I just wire pins B and C to gnd and/or put a resistor between them and ground to ensure they remain LOW?

2

Typical Connection Diagram (Fig-1) between 4051 and NodeMCU to suit OP's (@jdoto713 ) need.
4051Node
Figure-1:

3

What are the 2.2k pull-downs for?

Why do you label a crippled selection method as typical?

4
  1. To avoid floating conditions when sensors are not connected.
  2. I humbly delete the word typical from post #2.
5

Is that more valuable than an uninfluenced analog reading? Not for me.

6

Then I would increase the pull-down resistors to 20k each

7

Not using them at all would give the most accurate measurement.

8

If Senosr-2 is removed from Ch-1 for maintenance purposes while Ch-0 is kept in operation, then the channel cross talk (during switching) between Ch-0 and floating Ch-1 might be noticeable.

1 Like
9

not a silly question - but yes you can just ground them.

10

Thanks for the quick responses!

Great to hear I can save a few pins and ground the ones I wanted to always be LOW. I also did not explicitly ask, but see in that diagram I can do the same for the inhibit bit too.

11

That pin can only be grounded, which is in input mode.

12

yes

13

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