Using Python Periphery for GPIO Pins

[sslmorin]

Hi! I am currently working with an UpBoard, which has multiple GPIO pins similar to a Raspberry Pi. I have three push buttons attached to three GPIO pins, and then a common ground. The circuit is really simple, but all of the elements are connected, and they read as False when the button is pushed, True otherwise. I tested this with an LED instead of my code, and it seemed to work fine. But when I run my code, even when no button is pressed it outputs as though one was. Any ideas why this could be? `import time import datetime from periphery import GPIO gpio_good_in = GPIO(26, "in") gpio_neu_in = GPIO(6, "in")  gpio_bad_in = GPIO(5, "in")

good_condi = gpio_good_in.read() neu_condi = gpio_neu_in.read()   bad_condi = gpio_bad_in.read()   i= 1 while 1:  if not good_condi:print(Feedback: Good) elif not neu_condi:print(Feedback: Neutral) elif not bad_condi:print(Feedback: Bad) time.sleep(0.01) i = i+1 gpio_good_in.close()  gpio_neu_in.close() gpio_bad_in.close()`

[vsergeev]

Can you describe the connections in more detail? Do you have pull-ups on the GPIO side of the push buttons?

[sslmorin]

I am very new to hardware, and had no idea pull-ups were required for this circuit. After doing a bit of reading, I can see that I will need to add them. Thank you for letting me know!

[sslmorin]

@vsergeev I'm working on the same issue, but I noticed that there is a bias functionality built in to the GPIO class. However, when I put bias='pull_up' in the GPIO command, I get an unexpected keyword error. Would this work instead of rewiring my circuit, and if so how do I resolve the unexpected keyword error

[vsergeev]

The line bias option is a relatively new feature in Linux and is only available for character device GPIOs. See https://python-periphery.readthedocs.io/en/latest/gpio.html#periphery.periphery.GPIO.CdevGPIO for the constructor.

Assuming your GPIOs are available on gpiochip0, it would look like:

gpio_good_in = GPIO("/dev/gpiochip0", 26, "in", bias="pull_up")
gpio_neu_in = GPIO("/dev/gpiochip0", 6, "in", bias="pull_up")
gpio_bad_in = GPIO("/dev/gpiochip0", 5, "in", bias="pull_up")

If your kernel is too old, you might get an error opening with the bias option. In that case, I would still give it a try with an external pull-up (10k - 50k should be fine) to VCC to make sure there aren't other issues.

edit: fixed order of arguments in example

[sslmorin]

Thanks for all your help!

[vsergeev]

No problem. Feel free to reopen if you run into any other issues.