adc: Add Adc class

To abstract different ADC or sysfs API,

Note: later this class could land later in separate project
(ie: gpio, iotjs-node? sysfs-node?)
but since it's trivial let's share it here.

Relate-to: EnotionZ/gpio#53
Change-Id: I923159901d3af3e1990ccf3e1510d561c2e0783b
Signed-off-by: Philippe Coval <p.coval@samsung.com>

example/platform/adc/index.js

@@ -0,0 +1,28 @@
+// -*- mode: js; js-indent-level:2;  -*-
+// SPDX-License-Identifier: ISC
+/**
+ * Copyright 2018-present Samsung Electronics France SAS, and other contributors
+ *
+ * This Source Code Form is subject to the terms of the ICS Licence:
+ * https://spdx.org/licenses/ISC.html#licenseText
+ */
+
+const fs = require('fs');
+
+function Adc() {
+  this.open = function(config, callback) {
+    this.config = config;
+    fs.access(config.device, fs.R_OK, callback);
+    return this;
+  };
+
+  this.readSync = function() {
+    const contents = fs.readFileSync(this.config.device, 'ascii');
+    return contents;
+  };
+
+  this.closeSync = function() {
+  };
+}
+
+module.exports = new Adc();