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How do GPIO and reed switch interrupts work?
Using GPIO and reed switch to detect door state (open or closed) and state changes. I will first explain how interrupts work assuming everything has been configured properly, and then we will look at the various parts that need to be configured properly for the interrupt to work.
When does a GPIO change from 0 to 1?
For GPIO, the typical options are when the value changes from 0 to 1, when the value changes from 1 to 0, any change in value (i.e., 0 to 1 or 1 to 0 but doesn’t matter which), or when the value stays 1 or 0. Depending on the microcontroller, this can be done per pin or for all pins on the port.
How does an interrupt flag work in a GPIO?
In addition, some microcontrollers require that the pin of interest be configured as an input in order for the interrupt flag to be set when the event occurs (e.g., CC2544). Others (e.g., ATmega328P) will set the flag regardless of whether the pin is configured as an output or input.
How does the GPIO pin on the ATmega328P work?
The ATmega328P has two pins where you can change this individually. The other GPIO pins by default detect any change (0 to 1 or 1 to 0) on the pin. Recall that in the previous article where we illustrated how interrupts work, we assumed that the pin was configured to only detect changes from 1 to 0.
Do you put resistor between relay and GPIO?
It is recommended to set a small resistor between the Pi and the relay, but it is not absolutely necessary with 3V3. If you set 5V instead of 3.3V to VCC, you should definitely put one resistor each (~ 1kΩ) between the GPIOs and the IN pins.
How does the ACPI driver handle a GPIO interrupt?
The ACPI driver handles the listed GPIO interrupt and evaluates the Edge, Level or Event control method for it. The control method quiesces the hardware event, if necessary, and executes the required Notify operator on the event source device’s namespace node. Windows then sends the notification to the device’s driver.
How are the pins on a GPIO controller ordered?
The banks in a GPIO controller are ordered relative to their pins’ position within the controller-relative GPIO pin space. For example, bank 0 contains pins 0-31 on the controller, bank 1 contains pins 32-63, and so on. All banks have the same number of pins, except for the last bank, which might have fewer.