hello_7segment.c

/**
 * Copyright (c) 2020 Raspberry Pi (Trading) Ltd.
 *
 * SPDX-License-Identifier: BSD-3-Clause
 */

#include <stdio.h>
#include "pico/stdlib.h"
#include "hardware/gpio.h"

/*
  Our 7 Segment display has pins as follows:

  --A--
  F   B
  --G--
  E   C
  --D--

  By default we are allocating GPIO 2 to A, 3 to B etc.
  So, connect GOIP 2 to pin A on the 7 segment LED display etc. Don't forget
  the appropriate resistors, best to use one for each segment!

  Connect button so that pressing the switch connects the GPIO 9 (default) to
  ground (pull down)
*/

#define FIRST_GPIO 2
#define BUTTON_GPIO (FIRST_GPIO+7)

// This array converts a number 0-9 to a bit pattern to send to the GPIO's
int bits[10] = {
        0x3f,  // 0
        0x06,  // 1
        0x5b,  // 2
        0x4f,  // 3
        0x66,  // 4
        0x6d,  // 5
        0x7d,  // 6
        0x07,  // 7
        0x7f,  // 8
        0x67   // 9
};

/// \tag::hello_gpio[]
int main() {
    stdio_init_all();
    printf("Hello, 7segment - press button to count down!\n");

    // We could use gpio_set_dir_out_masked() here
    for (int gpio = FIRST_GPIO; gpio < FIRST_GPIO + 7; gpio++) {
        gpio_init(gpio);
        gpio_set_dir(gpio, GPIO_OUT);
        // Our bitmap above has a bit set where we need an LED on, BUT, we are pulling low to light
        // so invert our output
        gpio_set_outover(gpio, GPIO_OVERRIDE_INVERT);
    }

    gpio_init(BUTTON_GPIO);
    gpio_set_dir(BUTTON_GPIO, GPIO_IN);
    // We are using the button to pull down to 0v when pressed, so ensure that when
    // unpressed, it uses internal pull ups. Otherwise when unpressed, the input will
    // be floating.
    gpio_pull_up(BUTTON_GPIO);

    int val = 0;
    while (true) {
        // Count upwards or downwards depending on button input
        // We are pulling down on switch active, so invert the get to make
        // a press count downwards
        if (!gpio_get(BUTTON_GPIO)) {
            if (val == 9) {
                val = 0;
            } else {
                val++;
            }
        } else if (val == 0) {
            val = 9;
        } else {
            val--;
        }

        // We are starting with GPIO 2, our bitmap starts at bit 0 so shift to start at 2.
        int32_t mask = bits[val] << FIRST_GPIO;

        // Set all our GPIO's in one go!
        // If something else is using GPIO, we might want to use gpio_put_masked()
        gpio_set_mask(mask);
        sleep_ms(250);
        gpio_clr_mask(mask);
    }

    return 0;
}
/// \end::hello_gpio[]