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In most examples I’ve seen of wiring buttons to GPIO inputs, the button is wired so that when closed, a circuit is completed between the pin and ground, producing a low input on the pin. A pull-up resistor is used to default the input value to high. Code on the Pi can then detect low as a button push.
How does a GPIO function work on a Raspberry Pi?
A GPIO event in the Raspberry Pi Python GPIO library works by calling a Python function whenever an event is triggered. Such a function is called a callback function.
Where is the series resistor on a GPIO?
Good (safe) design would use a series resistor ( 1 kΩ ) in series with the pushbutton to limit current. For the reasons made by Adam Davis, it is preferable to connect the pushbutton to ground, and locate the protective resistor close to the GPIO pin.
Can a GPIO pin be connected to 3v3?
It is poor practice to connect a GPIO pin directly to either 3V3 or GND. The GPIO is bidirectional, and if programmed as an input this would cause no problems.
How to enable pull up and pull down in GPIO?
You enable these internal pull-ups/pull-downs at the time of setting up the port for input or output, by adding an extra, optional, argument to the GPIO.setup () function call. We’re using pull-down, so it’s pull_up_down=GPIO.PUD_DOWN. If you want/need pull-up you can change the PUD_DOWN for PUD_UP.
Can I connect GPIO to ground ( to use it as’smart’?
So, if you want to programmatically control a route to ground and only a small amount of current is involved, you can do it by toggling a pin between an output driven low (= to ground) and an input (= disconnected). A “small amount” here means <= ~20 mA; you may get away with a bit more.
How to set up GPIO port in RPi.gpio?
RPi.GPIO to the rescue. You enable these internal pull-ups/pull-downs at the time of setting up the port for input or output, by adding an extra, optional, argument to the GPIO.setup () function call. We’re using pull-down, so it’s pull_up_down=GPIO.PUD_DOWN. If you want/need pull-up you can change the PUD_DOWN for PUD_UP.
Can a GPIO be connected to 3v3 or GND?
It is poor practice to connect a GPIO pin directly to either 3V3 or GND. The GPIO is bidirectional, and if programmed as an input this would cause no problems. On the other hand if programmed as an output will cause excessive current to be drawn.
Why are there 8 ground pins on the Raspberry Pi?
In addition to @goldilocks answer, I would add that the ground pins have been strategically placed to make it easier to connect to specific functions with smaller connectors. For example, physical pins 17 and 25 are at opposite ends of the SPI0 bus pins. Check out the Raspberry Pi Pinout site for more information.