samples: Add ADC test

Observed on ARTIK055s:

    log: adc: update: 3920
    log: adc: update: 0xf50
    log: adc: update: 0b111101010000
    log: adc: update: 95%

    log: adc: update: 1779
    log: adc: update: 0x6f3
    log: adc: update: 0b011011110011
    log: adc: update: 43%

Change-Id: Ib37c5209373d7bb93b186826a04c28696bb895e3
Signed-off-by: Philippe Coval <p.coval@samsung.com>

samples/adc/index.js

@@ -0,0 +1,62 @@
+// -*- mode: js; js-indent-level:2;  -*-
+/* Copyright 2018-present Samsung Electronics Co., Ltd. and other contributors
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *     http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+var console = require('console');
+var log = console.log || function(arg) {};
+log(process);
+
+var adc = require('adc');
+
+function AdcTest(config)
+{
+  var self = this;
+  if (!config) {
+    config = { frequency: 1, adc: { device: '/dev/adc0', pin: 0}};
+  }
+  if (!adc || !config || !(config.adc)) {
+    throw 'error: adc: Invalid config: ' + adc;
+  }
+  config.frequency = config.frequency || 1;
+  config.range = config.range || 0xfff;
+  config.period = config.frequency && (1000. / config.frequency );
+  self.config = config;
+  self.port = adc.open(config.adc, function(err) {
+    log('log: adc: ready: ' + err);
+    if (err) {
+      console.error('error: adc: Fail to open pin: ' + config.adc.pin);
+      return null;
+    }
+    self.inverval = setInterval(function() {
+      var value = self.port.readSync();
+      log('log: adc: update: ' + Number(value));
+      log('log: adc: update: 0x' + Number(value).toString(16));
+      log('log: adc: update: 0b' + Number(value).toString(2));
+      value = Math.floor(100. * value / self.config.range);
+      log('log: adc: update: ' + value + '%');
+
+    }, self.config.period);
+  });
+
+  self.close = function() {
+    try {
+      self.inverval && clearInterval(self.inverval);
+      self.port && self.port.closeSync();
+    } catch(err) {
+      console.error('error: adc: close:' + err);
+    }
+  }
+}
+
+var test = new AdcTest();