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node_modules/i2c-bus/example/ds1621-async-callback.js

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+'use strict';
+
+const async = require('async');
+const i2c = require('../');
+
+const DS1621_ADDR = 0x48;
+const CMD_ACCESS_CONFIG = 0xac;
+const CMD_READ_TEMP = 0xaa;
+const CMD_START_CONVERT = 0xee;
+
+const toCelsius = rawTemp => {
+  const halfDegrees = ((rawTemp & 0xff) << 1) + (rawTemp >> 15);
+
+  if ((halfDegrees & 0x100) === 0) {
+    return halfDegrees / 2; // Temp +ve
+  }
+
+  return -((~halfDegrees & 0xff) / 2); // Temp -ve
+};
+
+const displayTemperature = _ => {
+  let i2c1;
+
+  async.series([
+    cb => i2c1 = i2c.open(1, cb),
+
+    // Enter one shot mode (this is a non volatile setting)
+    cb => i2c1.writeByte(DS1621_ADDR, CMD_ACCESS_CONFIG, 0x01, cb),
+
+    // Wait while non volatile memory busy
+    cb => {
+      const wait = _ => {
+        i2c1.readByte(DS1621_ADDR, CMD_ACCESS_CONFIG, (err, config) => {
+          if (err) {
+            return cb(err);
+          }
+          if (config & 0x10) {
+            return wait();
+          }
+          cb(null);
+        });
+      };
+
+      wait();
+    },
+
+    // Start temperature conversion
+    cb => i2c1.sendByte(DS1621_ADDR, CMD_START_CONVERT, cb),
+
+    // Wait for temperature conversion to complete
+    cb => {
+      const wait = _ => {
+        i2c1.readByte(DS1621_ADDR, CMD_ACCESS_CONFIG, (err, config) => {
+          if (err) {
+            return cb(err);
+          }
+          if ((config & 0x80) === 0) {
+            return wait();
+          }
+          cb(null);
+        });
+      };
+
+      wait();
+    },
+
+    // Display temperature
+    cb => {
+      i2c1.readWord(DS1621_ADDR, CMD_READ_TEMP, (err, rawTemp) => {
+        if (err) {
+          return cb(err);
+        }
+        console.log('temp: ' + toCelsius(rawTemp));
+        cb(null);
+      });
+    },
+
+    cb => i2c1.close(cb)
+  ], err => {
+    if (err) {
+      throw err;
+    }
+  });
+};
+
+displayTemperature();
+