samples/boards/microbit: Add sound sample

Add a sample demonstrating sound output using PWM to a piezo buzzer
connected to the external edge connector port P0.

Change-Id: I8c0902fd935f2eb3b9979476a7540e7a0216ca63
Signed-off-by: Johan Hedberg <johan.hedberg@intel.com>

samples/boards/microbit/sound/Makefile

@@ -0,0 +1,4 @@
+BOARD ?= bbc_microbit
+CONF_FILE = prj.conf
+
+include ${ZEPHYR_BASE}/Makefile.test

samples/boards/microbit/sound/README.rst

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+.. _microbit_sound:
+
+BBC micro:bit sound
+###################
+
+Overview
+********
+
+This is simple example demonstrating how to use a piezo buzzer connected
+to port P0 on the edge connector of the BBC micro:bit board. Note that
+the buzzer is not part of the main micro:bit board, rather it it needs
+to be separately acquired and connected. A well working example is the
+MI:Power board that has a piezo buzzer in addition to a coin-cell
+battery. Resellers of this board can be fairly easily found using online
+search.
+
+Building
+********
+
+The sample can be built as follows:
+
+.. code-block:: console
+
+   $ cd samples/boards/microbit/sound
+   $ make
+
+Sample Output
+=============
+
+This sample outputs sounds through a connected piezo buzzer based on
+button presses of the two main buttons. For each press the current
+output frequency will be printed on the 5x5 LED display.

samples/boards/microbit/sound/prj.conf

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+CONFIG_GPIO=y
+CONFIG_MICROBIT_DISPLAY=y
+CONFIG_PWM=y
+CONFIG_PWM_NRF5_SW=y

samples/boards/microbit/sound/src/Makefile

@@ -0,0 +1 @@
+obj-y = main.o

samples/boards/microbit/sound/src/main.c

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+/*
+ * Copyright (c) 2017 Intel Corporation
+ *
+ * SPDX-License-Identifier: Apache-2.0
+ */
+
+#include <zephyr.h>
+#include <misc/printk.h>
+#include <board.h>
+#include <gpio.h>
+#include <pwm.h>
+#include <device.h>
+
+#include <display/mb_display.h>
+
+#define BUZZER_PIN     EXT_P0_GPIO_PIN
+
+#define PERIOD_MIN     50
+#define PERIOD_MAX     3900
+#define PERIOD_INIT    1500
+
+#define BEEP_DURATION  K_MSEC(60)
+
+#define US_TO_HZ(_us)  (USEC_PER_SEC / (_us))
+
+static struct device *pwm;
+static struct device *gpio;
+static uint32_t period = PERIOD_INIT;
+static struct k_work beep_work;
+static volatile bool beep_active;
+
+static void beep(struct k_work *work)
+{
+	/* The "period / 2" pulse duration gives 50% duty cycle, which
+	 * should result in the maximum sound volume.
+	 */
+	pwm_pin_set_usec(pwm, BUZZER_PIN, period, period / 2);
+	k_sleep(BEEP_DURATION);
+
+	/* Disable the PWM */
+	pwm_pin_set_usec(pwm, BUZZER_PIN, 0, 0);
+
+	/* Ensure there's a clear silent period between two tones */
+	k_sleep(K_MSEC(50));
+	beep_active = false;
+}
+
+static void button_pressed(struct device *dev, struct gpio_callback *cb,
+			   uint32_t pins)
+{
+	struct mb_display *disp;
+
+	if (beep_active) {
+		printk("Button press while beeping\n");
+		return;
+	}
+
+	beep_active = true;
+
+	if (pins & BIT(SW0_GPIO_PIN)) {
+		printk("A pressed\n");
+		if (period < PERIOD_MAX) {
+			period += 50;
+		}
+	} else {
+		printk("B pressed\n");
+		if (period > PERIOD_MIN) {
+			period -= 50;
+		}
+	}
+
+	printk("Period is %u us (%u Hz)\n", period, US_TO_HZ(period));
+
+	disp = mb_display_get();
+	mb_display_print(disp, MB_DISPLAY_MODE_DEFAULT, K_MSEC(500), "%uHz",
+			 US_TO_HZ(period));
+
+	k_work_submit(&beep_work);
+}
+
+void main(void)
+{
+	static struct gpio_callback button_cb;
+
+	gpio = device_get_binding(SW0_GPIO_NAME);
+
+	gpio_pin_configure(gpio, SW0_GPIO_PIN,
+			   (GPIO_DIR_IN | GPIO_INT | GPIO_INT_EDGE |
+			    GPIO_INT_ACTIVE_LOW));
+	gpio_pin_configure(gpio, SW1_GPIO_PIN,
+			   (GPIO_DIR_IN | GPIO_INT | GPIO_INT_EDGE |
+			    GPIO_INT_ACTIVE_LOW));
+	gpio_init_callback(&button_cb, button_pressed,
+			   BIT(SW0_GPIO_PIN) | BIT(SW1_GPIO_PIN));
+	gpio_add_callback(gpio, &button_cb);
+
+	pwm = device_get_binding(CONFIG_PWM_NRF5_SW_0_DEV_NAME);
+
+	k_work_init(&beep_work, beep);
+	/* Notify with a beep that we've started */
+	k_work_submit(&beep_work);
+
+	gpio_pin_enable_callback(gpio, SW0_GPIO_PIN);
+	gpio_pin_enable_callback(gpio, SW1_GPIO_PIN);
+}

samples/boards/microbit/sound/testcase.ini

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+[test]
+build_only = true
+tags = samples
+platform_whitelist = bbc_microbit