Simple button is not working

[greenreader9]

Hello!

I am fairly new to microcontrollers, but have successfully programed a short script (CircuitPython) in the past, and I have absolutely no clue what is going on here (With MicroPython).

The board is a Raspberry Pi Pico W running version 20220914-unstable-v1.19.1-409-g0e8c2204d installed with Thonny (See screenshot below)

My code is:

from machine import Pin

btn = Pin(0, Pin.IN)

while True:
    if btn() == 1:
        print("pushed")
    else:
        print("Not pushed")

Looking at this image, I am using 1 ( GPO 0) and 36 (3V3(OUT)).

Since the button does not seem to work right at all, I just removed it and tried the below to see how the output changes when I changed the input.

So here are the four things I have done, and what happens when I do them:

1. Nothing (So just run the program with nothing attached): Not Pushed is printed repeatedly (So this works)
2. Connect GPO 0 to 3V3(OUT) with a jumper cable: Pushed is printed repeatedly (So this works)
3. Start with nothing connected, then connect GPO 0 to 3V3(OUT) with a jumper cable: Not Pushed is printed repeatedly (So this does not work right, since it should switch to Pushed when I add in the jumper cable)
4. Start with GPO 0 and 3V3(OUT) connected with a jumper cable, then disconnect them: Pushed is printed repeatedly (So this does not work right, since it should switch to Not Pushed when I remove the jumper cable)

So for some reason it always just prints whatever it's initial state was, why is this?

Apologies if the answer is really really simple, but nothing I find on the internet seems to work at all.

Thanks in advance!

[davefes]

Try changing:

if btn() == 1:

to

if btn.value() == 1:

[greenreader9]

No, that did not work. Still the same behavior unfortunately.

[davefes]

OK, I am working through a similar issue where GPIO state is unchanged on doing a CTRL-C in rshell.

Something else to try before your while loop:

btn.off()

then at least you know what state you are starting off in.

[greenreader9]

Assuming this is what you meant:

from machine import Pin

btn = Pin(0, Pin.IN)
btn.off()

while True:
    if btn.value() == 1:
        print("pushed")
    else:
        print("Not pushed")

It still does not work, returning the same results as before

[davefes]

After

btn.off()

put

print (' btn state = ', btn.value())

Sorry, I don't use Thonny so maybe I am missing something there.

[robert-hh]

Do you have an external pull resistor to define the button open state? You do not use the pull= in your code. If the button connects the input to Vcc, you need a pull-down default, if it connects to GND, you need pull-up. You can at least try with the internal pull options:
btn = Pin(0, Pin.IN, pul=Pin.PULL_DOWN) for a pull-down or btn = Pin(0, Pin.IN, pull=PULL_UP) for pull-up.

[steveh127]

I can confirm Roberts code works as expected or almost, there are a couple of obvious and minor typos in Roberts code. btn=Pin(0, Pin.IN, pull=Pin.PULL_DOWN ) and you don't need the pull= so btn=Pin(0,Pin.IN,Pin.PULL_UP) works too. Tested on a Pico W.

[greenreader9]

Now using this:

from machine import Pin

btn=Pin(0, Pin.IN, pull=Pin.PULL_DOWN )
btn.off()

while True:
    print (' btn state = ', btn.value())

Still has the same behavior as before...

[greenreader9]

I figured it out.

For future reference, this worked for me:

from machine import Pin

btn = machine.Pin(0, machine.Pin.IN, machine.Pin.PULL_DOWN)

last_state = False
current_state = False

while True:
    current_state = btn.value()
    if last_state == False and current_state == True:
        print ('pushed')
    last_state = current_state

Thanks to everyone that replied!

[puppet13th]

there is 2 methods you can use for simple button:

machine.Pin.PULL_DOWN ==> set default pin state to low
machine.Pin.PULL_UP ==> set default pin state to high

PULL_DOWN scenario
wiring : [Pin.IN] -- [button/swtich] -- [3.3v]
not pressed value = 0
pressed value = 1

while True:
    if btn.value() == 1:
        print('button pressed')

PULL_UP scenario
wiring : [Pin.IN] -- [button/swtich] -- [GND]
not pressed value = 1
pressed value = 0

while True:
    if btn.value() == 0:
        print('button pressed')

[jimmo]

Just FYI @davefes @greenreader9 -- pin() and pin.value() are equivalent. The former is marginally more efficient in terms of how the VM executes it, but I think the latter is clearer.
(In Python terminology, machine.Pin objects implement the __call__ operator).