Arduino Library for Microchip MCP9808 Maximum Accuracy Digital Temperature Sensor

https://github.com/JChristensen/MCP9808
ReadMe file
Jack Christensen Jun 2015

Introduction

Arduino Library for Microchip MCP9808 Maximum Accuracy Digital Temperature Sensor

A lightweight implementation that exposes all functionality of the Microchip MCP9808 sensor. Temperatures are handled in the integer domain to avoid the code size and runtime overhead associated with floating-point. Should the user wish to work in floating-point format, conversion is easily done in the application code.

The ambient temperature is read as °C*16. If a lower resolution is configured, the applicable low-order bits are returned as zeroes.

The Upper, Lower and Critical temperature limit registers are read and written as °C*4.

Bit masks for the config register are provided in the MCP9808.h file.

"Arduino Library for Microchip MCP9808 Temperature Sensor" by Jack Christensen is licensed under CC BY-SA 4.0.

Examples

The following example sketch is included with the MCP9808 library:

• MCP9808_EX1: Demonstrates reading data from the sensor and changing the temperature limit registers. Converts the ambient temperature reading to floating point in °C and °F.

Enumeration

twiClockFreq_t

Description

Symbolic names for I2C bus speeds.

Values

• MCP9808::twiClock100kHz -- 100kHz bus speed.
• MCP9808::twiClock400kHz -- 400kHz bus speed.

Constructor

MCP9808(uint8_t LS_ADDR_BITS)

Description

Instantiates an MCP9808 sensor object.

Syntax

MCP9800 mySensor(0);
// or
MCP9800 mySensor;

Parameters

LS_ADDR_BITS: An unsigned 8-bit integer (uint8_t or byte) representing the least-significant three bits of the I2C device address (i.e. a value between 0 and 7). Defaults to zero if omitted.

Methods

begin(twiClockFreq_t twiFreq)

Description

Initializes the library. Calling begin() calls read() to initially populate the sensor data into local storage. Call this method once in the setup code.

Syntax

mySensor.begin(twiClockFreq_t freq);

Parameters

twiFreq: An optional parameter specifying the speed for the I2C bus. If omitted, it defaults to 100kHz (MCP9808::twiClockFreq_t)

Returns

I2C status (zero if successful) (uint8_t).

Example

MCP9808 mySensor;
mySensor.begin(MCP9808::twiClock400kHz);

read()

Description

Reads data from the sensor into local storage. See Properties below for a description of the data.

Syntax

mySensor.read();

Parameters

None.

Returns

I2C status (zero if successful) (uint8_t).

Example

MCP9808 mySensor;
mySensor.begin();
uint8_t e = mySensor.read();
if ( e != 0 )
{
	//there was an error on the bus
}
else
{
	//all is well
}

write()

Description

Writes data from local storage to the sensor. Note that only the three critical temperature registers, the configuration register and the resolution register are written; other registers are read-only.

Syntax

mySensor.write();

Parameters

None.

Returns

I2C status (zero if successful) (uint8_t).

Example

MCP9808 mySensor;
mySensor.begin();
mySensor.tUpper = 100;    //set upper limit to 25C (77F)
mySensor.write();

Properties

tUpper: Upper temperature limit, in units of °C*4. (int16_t)
tLower: Lower temperature limit, in units of °C*4. (int16_t)
tCritical: Critical temperature limit, in units of °C*4. (int16_t)
tAmbient: Ambient temperature, in units of °C*16. Read-only. (int16_t)
config: Configuration register, see datasheet for details. (uint16_t)
resolution: Temperature resolution for the ambient temperature. An integer between 0 and 3, where 0 is ±0.5°C, 1 is ±0.25°C, 2 is ±0.125°C, and 3 is ±0.0625°C. Higher resolutions require longer conversion times, see the datasheet. ±0.0625°C is the power-on default. (uint8_t)
alertCritical: If tAmbient ≥ tCritical, then true, else false. Read-only. (bool)
alertUpper: If tAmbient > tUpper, then true, else false. Read-only. (bool)
alertLower: If tAmbient < tLower, then true, else false. Read-only. (bool)
mfrID: Manufacturer ID. Read-only. (uint16_t)
deviceID: Device ID. Read-only. (uint8_t)
deviceRev: Device revision. Read-only. (uint8_t)