MCP9808 precision I2C temperature sensor

This is a module that makes it easy to connect to a MCP9808 Precision I2C Temperature sensor.

The MCP9808 is a precision I2C temperature sensor from Microchip between -20°C and +100°C with +- 0.25°C / +- 0.5°C (typical/maximum) accuracy. This module makes it easy to connect this sensor with an espruino board.

Use the MCP9808 module for it.

Wiring Up

Pin	Espruino
GND	GND
VCC	3.3v
SDA	B7
SCL	B6
ALERT	Open-Drain-Output
A2	GND or 3.3v
A1	GND or 3.3v
A0	GND or 3.3v

Software

How to use the module:

I2C1.setup({scl:B6,sda:B7, bitrate: 60000});
var mcp = require("MCP9808").connect(I2C1, 0b000); // 0b000 means A2 = A2 = A1 = GND 
var temperature = mcp.getTemperature();
console.log("Temperature: " + temperature + " C");

The sensor can handle bitrates up to 400000 but I had stability problems with this.

Reference

/* returns the current sensor resolution as enum
 *     MCP9808.RESOLUTION_0_5_CELSIUS   0.5°C,    approx.  30 ms
 *     MCP9808.RESOLUTION_0_25_CELSIUS  0.25°C,   approx.  65 ms
 *     RESOLUTION_0_125_CELSIUS         0.125°C,  approx. 130 ms
 *     RESOLUTION_0_0625_CELSIUS        0.0615°C  approx. 250 ms
 */
MCP9808.prototype.getResolution = function () { ... }

/* set the current sensor resolution
 * Allowed values are:
 *     MCP9808.RESOLUTION_0_5_CELSIUS   0.5°C,    approx.  30 ms
 *     MCP9808.RESOLUTION_0_25_CELSIUS  0.25°C,   approx.  65 ms
 *     RESOLUTION_0_125_CELSIUS         0.125°C,  approx. 130 ms
 *     RESOLUTION_0_0625_CELSIUS        0.0615°C  approx. 250 ms
 */
MCP9808.prototype.setResolution = function (resolution) { ... }

/* return the temperature in °C
 */
MCP9808.prototype.getTemperature = function () { ... }

/* return whether the sensor is running or in power down mode
 * true if the sensor is running
 */
MCP9808.prototype.isRunning = function () { ... }

/* wakeup the sensor from power down mode
 */
MCP9808.prototype.wakeup = function () { ... }

/* Set the sensor in power down mode
 * The temperature can be read but will not be updated anymore.
 */
MCP9808.prototype.shutdown = function () { ... }

/* returns whether a configured limit temperature (lower, upper, critical) is reached
 * {
 *     aboveCriticalLimit: true/false,
 *     aboveUpperLimit: true/false,
 *     belowLowerLimit: true7false
 * }
 */
MCP9808.prototype.getAlertStatus = function () { ... }

/* get the hysteresis for alerts in °C
 * If an alert has triggered and alert mode is CHECK_ALL_LIMITS_COMPARATOR or CHECK_CRITICAL_LIMIT
 * the current temperature must below the limit temperature minus hysteresis.
 * This avoids the flickering of the ALERT pin when temperature is around a configured limit temperature.
 *
 * Only 4 different values are supported. Possible return values would be
 *   0.0°C, 1.5°C, 3.0°C or 6.0°C.
 *
 */
MCP9808.prototype.getHysteresis = function () { ... }

/* set the hysteresis for alerts in °C
 * Only 4 different values are supported: 0.0°C, 1.5°C, 3.0°C or 6.0°C.
 */
MCP9808.prototype.setHysteresis = function (celsius) { ... }

/* returns whether the ALERT pin goes high or low when an temperature alert occurs.
 * returns true is the ALERT pin goes high when an temperature alert occurs.

 * Hint: The ALERT pin is an open-drain-output. At least a pull-up resistor is required!
 */
MCP9808.prototype.isAlertHighActive = function () { ... }

/* set the output polarity of the ALERT pin
 *   true - the ALERT pin goes high when ALERT occurs
 *   false - the ALERT pin goes low when ALERT occurs
 *
 * Hint: The ALERT pin is an open-drain-output. At least a pull-up resistor is required!
 */
MCP9808.prototype.setAlertHighActive = function (highActive) { ... }

/* If the sensor is in alert mode MCP9808.CHECK_ALL_LIMITS_INTERRUPT then the alert will not
 * disapper when the temperature is in a valid range again.
 * Only a call the clearInterrupt() will reset the alert.
 */
MCP9808.prototype.clearInterrupt = function () { ... }

/* get the configured alert mode. Possible return values are
 *   MCP9808.DISABLED
 *   MCP9808.CHECK_ALL_LIMITS_COMPARATOR
 *   MCP9808.CHECK_ALL_LIMITS_INTERRUPT
 *   MCP9808.CHECK_CRITICAL_LIMIT
 */
MCP9808.prototype.getAlertMode = function () { ... }

/* set the alert mode, Allowed values . Possible are
 *   MCP9808.DISABLED
 *   MCP9808.CHECK_ALL_LIMITS_COMPARATOR
 *   MCP9808.CHECK_ALL_LIMITS_INTERRUPT
 *   MCP9808.CHECK_CRITICAL_LIMIT
 */
MCP9808.prototype.setAlertMode = function (mode) { ... }

/* returns if a configure temperature alert has occured
 */
MCP9808.prototype.hasAlert = function () { ... }

/* get the lower temperature limit to trigger an alert
 * The default value after reset is 0°C.
 */
MCP9808.prototype.getAlertLowerLimit = function () { ... }

/* Set the lower temperature limit to trigger an alert.
 * @param temperature lower limit in celsius
 */
MCP9808.prototype.setAlertLowerLimit = function (temperature) { ... }

/* get the upper temperature limit to trigger an alert
 * The default value after reset is 0°C.
 */
MCP9808.prototype.getAlertUpperLimit = function () { ... }

/* Set the upper temperature limit to trigger an alert.
 * @param temperature upper limit in celsius
 */
MCP9808.prototype.setAlertUpperLimit = function (temperature) { ... }

/* get the critical temperature limit to trigger an alert
 * The default value after reset is 0°C.
 */
MCP9808.prototype.getAlertCriticalLimit = function () { ... }

/* Set the critical temperature limit to trigger an alert.
 * @param temperature critical limit in celsius
 */
MCP9808.prototype.setAlertCriticalLimit = function (temperature) { ... }

// Read 1 byte from register reg
MCP9808.prototype.read8 = function (reg) { ... }

// Read two  bytes from register reg and combine to unsigned integer
MCP9808.prototype.read16 = function (reg) { ... }

// Write one byte (value) to register reg
MCP9808.prototype.write8 = function (reg, value) { ... }

// Write an unsigned integer value (two bytes) to register reg
MCP9808.prototype.write16 = function (reg, value) { ... }

exports.connect = function (i2c, a2a1a0Pins) { ... }

Buying

• Adafruit

Links

• Manufacturer
• Datasheet