References: Digital Input, Output, and Interrupts
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General-purpose input/output - Wikipedia - Explains GPIO pins and how software reads and writes them. Directly supports this chapter's LED-output and button-input work.
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Interrupt - Wikipedia - Describes how hardware signals pause normal code to handle urgent events. Background for the chapter's interrupt and ISR section.
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Pull-up resistor - Wikipedia - Covers pull-up and pull-down resistors that keep a floating input at a known level. Reinforces the chapter's button-wiring and debouncing topics.
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Get Started with MicroPython on Raspberry Pi Pico - Gareth Halfacree & Ben Everard - Raspberry Pi Press - The official book's I/O chapters cover blinking LEDs and reading buttons with the exact
machine.Pinpatterns used here. -
Programming the Raspberry Pi Pico/W in MicroPython - Harry Fairhead & Mike James - I/O Press - A deeper treatment of GPIO, pull resistors, and interrupts that extends the concepts introduced in this chapter.
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machine.Pin - MicroPython - Official reference for configuring pins as input or output, setting pull resistors, and attaching interrupts. The authoritative companion to this chapter's code.
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Pull-up Resistors - SparkFun - A clear tutorial on why floating inputs are a problem and how pull resistors fix them. Reinforces the chapter's button-input wiring.
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Writing Interrupt Handlers - MicroPython - Official rules for writing safe, short interrupt service routines. Essential reading for the chapter's interrupt examples.
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Raspberry Pi Pico External Interrupts - Random Nerd Tutorials - A hands-on Pico interrupt tutorial with wiring and MicroPython code. Great practice for the chapter's IRQ section.
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Interrupts - GeeksforGeeks - Explains interrupt types and how processors service them. Provides additional background for the chapter's interrupt-driven input.