Multiple pins serial read from Arduino to Python

Projects General Guidance
1

Hi guys !
I’m new to this forum and to Arduino altogether, so please bear with me. I need some help for an ongoing project. I have 8 pins on my Arduino from which i am getting digital reads (so either HIGH=1 or LOW=0).
I would need to import those readings in Python, so that i can do something like this :

if pin1=1
then value1=1
else value1=0

if pin 2=1
then value2=2
else value2=0

if pin3=1
then value3=4
else value3=0

etc…

and then get a final value by adding them together
total = value1 + value2 + value3+….

and do some other stuff, like retrieving line[total] from a text file and so on…

But I don’t really know how to go about getting the results from the digital reads in Python, I checked a bit around, and it seems like I could import the serial from the arduino, but then I would loose the relation between the pin and the pin state (wouldn’t I ?), and I would need to reassign them… And that sounds like quite a bit of trouble for something that feels pretty simple and straightforward to me.

Any advice would be very welcome !
Thanks !

2

I checked a bit around, and it seems like I could import the serial from the arduino

Yes.

but then I would loose the relation between the pin and the pin state (wouldn't I ?),

No.
The pin position is given by the bit position in the number you send. Think binary.

3

This Python - Arduino demo may be of interest.

You could convert each I/O pin into a different bit in a single byte using a Bitshift

Alternatively you could send the values to python individually but always in the same order - something like

Serial.print('<');
Serial.print(value1);
Serial.print(','); // comma separator
Serial.print(value2);
Serial.print(',');
// etc
Serial.println('>');

...R

4

You could convert each I/O pin into a different bit in a single byte using a Bitshift

Yes but that pseudo code he gave is in effect doing that already.

5

Grumpy_Mike:
Yes but that pseudo code he gave is in effect doing that already.

You are correct. I did not spot that.

...R

6

Grumpy_Mike:
The pin position is given by the bit position in the number you send. Think binary.

You're right, I was not thinking about it the right way

Robin2:
You could convert each I/O pin into a different bit in a single byte using a Bitshift

That would actually shorten the process by not having to attribute and add up values, I would just need to capture the whole string of the pins outputs and convert it to an integer. And I can go back for individual outputs when it's relevant.

Grumpy_Mike:
Yes but that pseudo code he gave is in effect doing that already.

The code looks silly, right ? I was sketching out how I was thinking about it.

Thanks to you both !

7

The code looks silly, right ?

No it's pseudo code, you get the idea but the syntax is not correct that is all.
I would have ORed the individual values together if it were me rather than add them but it produces the same result. Oddly enough just last week I wrote the same sort of thing in Python :-

#Python code to read four GPIO pins into a number
def getSensor():
   sensor = 0
   for pin in range(0,4):
      sensor = (sensor << 1) | ( io.digitalRead(inputPins[pin]))
   return sensor