button.c (button sample)

/** * Copyright (c) 2020 Raspberry Pi (Trading) Ltd. * * SPDX-License-Identifier: BSD-3-Clause */ #include <stdio.h> #include "pico/stdlib.h" #include "hardware/gpio.h" #include "hardware/sync.h" #include "hardware/structs/ioqspi.h" #include "hardware/structs/sio.h" // This example blinks the Pico LED when the BOOTSEL button is pressed. // // Picoboard has a button attached to the flash CS pin, which the bootrom // checks, and jumps straight to the USB bootcode if the button is pressed // (pulling flash CS low). We can check this pin in by jumping to some code in // SRAM (so that the XIP interface is not required), floating the flash CS // pin, and observing whether it is pulled low. // // This doesn't work if others are trying to access flash at the same time, // e.g. XIP streamer, or the other core. bool __no_inline_not_in_flash_func(get_bootsel_button)() { const uint CS_PIN_INDEX = 1; // Must disable interrupts, as interrupt handlers may be in flash, and we // are about to temporarily disable flash access! uint32_t flags = save_and_disable_interrupts(); // Set chip select to Hi-Z hw_write_masked(&ioqspi_hw->io[CS_PIN_INDEX].ctrl, GPIO_OVERRIDE_LOW << IO_QSPI_GPIO_QSPI_SS_CTRL_OEOVER_LSB, IO_QSPI_GPIO_QSPI_SS_CTRL_OEOVER_BITS); // Note we can't call into any sleep functions in flash right now for (volatile int i = 0; i < 1000; ++i); // The HI GPIO registers in SIO can observe and control the 6 QSPI pins. // Note the button pulls the pin *low* when pressed. #if PICO_RP2040 #define CS_BIT (1u << 1) #else #define CS_BIT SIO_GPIO_HI_IN_QSPI_CSN_BITS #endif bool button_state = !(sio_hw->gpio_hi_in & CS_BIT); // Need to restore the state of chip select, else we are going to have a // bad time when we return to code in flash! hw_write_masked(&ioqspi_hw->io[CS_PIN_INDEX].ctrl, GPIO_OVERRIDE_NORMAL << IO_QSPI_GPIO_QSPI_SS_CTRL_OEOVER_LSB, IO_QSPI_GPIO_QSPI_SS_CTRL_OEOVER_BITS); restore_interrupts(flags); return button_state; } int main() { #ifndef PICO_DEFAULT_LED_PIN #warning picoboard/button example requires a board with a regular LED #else gpio_init(PICO_DEFAULT_LED_PIN); gpio_set_dir(PICO_DEFAULT_LED_PIN, GPIO_OUT); while (true) { gpio_put(PICO_DEFAULT_LED_PIN, get_bootsel_button() ^ PICO_DEFAULT_LED_PIN_INVERTED); sleep_ms(10); } #endif }