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