samples: Added analog_input sample

Add a sample to demonstrate how to use analogRead API

Signed-off-by: TOKITA Hiroshi <[email protected]>

samples/analog_input/CMakeLists.txt

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+# SPDX-License-Identifier: Apache-2.0
+
+cmake_minimum_required(VERSION 3.20.0)
+
+set(DTC_OVERLAY_FILE $ENV{ZEPHYR_BASE}/../modules/lib/Arduino-Zephyr-API/variants/${BOARD}/${BOARD}.overlay)
+
+find_package(Zephyr REQUIRED HINTS $ENV{ZEPHYR_BASE})
+project(analog_input)
+
+target_sources(app PRIVATE src/main.cpp)
+zephyr_compile_options(-Wno-unused-variable -Wno-comment)

samples/analog_input/README.rst

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+.. _analog_input:
+
+Analog Input
+############
+
+Overview
+********
+
+The analog_input sample blinks the LED with control of the period
+by the voltage of the input pin.
+Inputting high voltage to blink the LED slowly.
+Blink the LED fast on input voltage is low.
+When the input is 0V, LED light.
+
+Building and Running
+********************
+
+Build and flash analog_input sample as follows,
+
+```sh
+$> west build -p -b arduino_nano_33_ble sample/analog_input/
+
+$> west flash --bossac=/home/$USER/.arduino15/packages/arduino/tools/bossac/1.9.1-arduino2/bossac
+```

samples/analog_input/prj.conf

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+CONFIG_ADC=y
+CONFIG_ARDUINO_API=y

samples/analog_input/src/main.cpp

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+/*
+ * Copyright (c) 2022 TOKITA Hiroshi <[email protected]>
+ *
+ * SPDX-License-Identifier: Apache-2.0
+ */
+
+#include <Arduino.h>
+
+const int analog_input = A0;    // select the input pin for the potentiometer
+const int ledPin = LED_BUILTIN;      // select the pin for the LED
+const float wait_factor = 1.f;
+
+void setup() {
+  pinMode(ledPin, OUTPUT);
+}
+
+void loop() {
+  int value = 0;
+
+  value = analogRead(analog_input);
+
+  /* Blinks slowly when the input voltage is high */
+
+  digitalWrite(ledPin, HIGH);
+  delay(value * wait_factor);
+
+  digitalWrite(ledPin, LOW);
+  delay(value * wait_factor);
+}