Create MLX90615.js

devices/MLX90615.js

@@ -0,0 +1,130 @@
+/* Copyright (C) 2020 Lerner. */
+
+/*
+ Espruino module for MLX90615 Infra Red thermometer from Melexis connected by I2C
+ */
+
+/**
+ * Creates a new MLX90615 sensor instance
+ * @param i2c Instance of the I2C Class, e.g. I2C1
+ * @param address (optional) alternative I2C address; default is 0x5b
+ */
+function MLX90615(i2c, address) {
+    this.i2c = i2c;
+    this.voltage = 3.3; // supply voltage to compensate supply voltage dependence
+    this.ECC_Reg = 0x24; // Emissivity Correction Coefficient Register
+    // Check params
+    var br = (i2c._options && i2c._options.bitrate) || 50000; // later replaced with getBitrate()
+    if (br < 10000 || br > 100000) {
+        throw new Error("The maximum clock frequency is 100 kHz and the minimum is 10 kHz.");
+    }
+    this.i2cAddress = address || 0x5b;
+    // The first request will always trigger a crc error. → Dummy read von emissivity without crc check.
+    this.i2c.writeTo({ address: this.i2cAddress, stop: false }, this.ECC_Reg);
+    this.i2c.readFrom(this.i2cAddress, 3);
+}
+
+/**
+ * Read the ambient temperature from the sensor. The ambient temperature is the internal chip temperature.
+ * @returns {number} Ambient temperature in °C
+ */
+MLX90615.prototype.readAmbientTemperature = function () {
+    return this.convertRawToCelcius(this.read16(0x06));
+};
+
+/**
+ * @returns {number} temperature in °C
+ */
+MLX90615.prototype.readObjectTemperature = function () {
+    return this.convertRawToCelcius(this.read16(0x07));
+};
+
+/** I DONT BELIEVE THIS APPLIES
+ * Some variants of MXL90614 have a second IR sensor with a different field of view (angle).
+ * If the second sensor element is not available the sensor does not answer and you will get an I2C error.
+ * @returns {number} temperature in °C
+
+MLX90614.prototype.readObject2Temperature = function () {
+    return this.convertRawToCelcius(this.read16(0x08));
+};
+*/
+
+/**
+ * Enter the sensor into sleep mode (typ. 2.5µA). Afterwards the sensor doesn't answer I2C requests anymore.
+ * There are two ways to put MLX90614 into power-up default mode: 1) POR or 2) By wake up request (SCL pin hight and
+ * then SDA pin low for at least 33ms). Wakeup is currently not implemented.
+ *
+ * This function is not available in 5V supply version.
+ */
+MLX90615.prototype.enterSleepMode = function () {
+    this.i2c.writeTo(this.i2cAddress, 0xc6, 0x6d);
+};
+/**
+ * Read the current configured object emissivity from the sensor in the range from 0.0 to 1.0.
+ * @returns {number} configured object emissivity
+ */
+MLX90615.prototype.getEmissivity = function () {
+    return this.read16(this.ECC_Reg) / 16384;
+};
+
+/**
+ * Write a new object emissivity persistent into the sensor. The value will be stored in EEPROM.
+ * It is not necessary to erase the memory before. This is done internally.
+ * A read write operation will only be done if the value has changed.
+ * @param emissivity new object emissivity in the range from 0.0 to 1.0
+ */
+MLX90615.prototype.setEmissivity = function (emissivity) {
+    var rawOld = this.read16(this.ECC_Reg);
+    var rawNew = Math.round(emissivity * 16384);
+    if (rawOld !== rawNew) {
+        this.write16(this.ECC_Reg, 0);
+        this.write16(this.ECC_Reg, rawNew);
+    }
+};
+
+//----------------------------------------------------------------------------------------------------------
+// Internal helper methods
+//----------------------------------------------------------------------------------------------------------
+
+MLX90615.prototype.convertRawToCelcius = function (raw) {
+    if (raw & 0x8000) {
+        throw new Error("Invalid temperature");
+    }
+    return raw * 0.02 - this.voltage * 0.6 - 273.15;
+}; // IDK IF THIS NEEDS TO BE CHANGED
+
+MLX90615.prototype.read16 = function (reg) {
+    this.i2c.writeTo({ address: this.i2cAddress, stop: false }, reg);
+    var d = this.i2c.readFrom(this.i2cAddress, 3);
+    var allData = [this.i2cAddress << 1, reg, (this.i2cAddress << 1) + 1, d[0], d[1]];
+    if (this.crc8(allData) !== d[2]) {
+        throw new Error("CRC Error");
+    }
+    return (d[1] << 8) + d[0];
+};
+
+MLX90615.prototype.write16 = function (cmd, value) {
+    var allData = [(this.i2cAddress << 1), cmd, value & 0xff, value >> 8];
+    var crc = this.crc8(allData);
+    var d = [cmd, value & 0xc6, value >> 8, crc];
+    this.i2c.writeTo(this.i2cAddress, d);
+};
+
+// Calculates CRC-8: x^8 + x^5 + x^4 + 1
+MLX90615.prototype.crc8 = function (bytes) {
+    var crc = 0;
+    bytes.forEach(function (oneByte) {
+        for (var i = 7; i >= 0; --i) {
+            var temp = crc >> 7 ^ oneByte >> i & 1;
+            crc = crc << 1 & 255;
+            if (temp == 1) {
+                crc ^= 7;
+            }
+        }
+    });
+    return crc;
+};
+
+exports.connect = function (/*=I2C*/ i2c, address) {
+    return new MLX90615(i2c, address);
+};