GY-63_MS5611/libraries/MCP9808_RT

MCP9808_RT

Arduino library for I2C MCP9808 temperature sensor

Description

The MCP9808 is a temperature sensor that measures typically in 1/16th == 0.0625 of a degree celsius. What makes this sensor interesting is the ALERT pin, which allows triggering of any piece of electronics if the temperature hits a predefined value or zone.

MCP9808 breakout board

//
//  Adafruit MCP9808 breakout board
//  +----------+
//  |0   ALERT |---------------+--[ 4K7 ]---- +5V
//  |       A2 |---- GND       |
//  |       A1 |---- GND       +--[ LED ]---- GND  // or other electronics.
//  |       A0 |---- GND
//  |      SDA |---- I2C MCU
//  |      SCL |---- I2C MCU
//  |      GND |---- GND MCU
//  |0     VCC |---- +5V
//  +----------+
//
//  address above is 24
//

Interface

Constructor

• MCP9808(const uint8_t addr) constructor for e.g. UNO
• MCP9808(const uint8_t addr, const uint8_t dataPin = 255, const uint8_t clockPin = 255) constructor for ESP32 and ESP8266
• setAddress(const uint8_t address, TwoWire *wire) if multiple I2C busses are present one can choose.

Address max 8 sensors on one I2C bus Normal address = 0011xxx where xxx = A2, A1, A0

Address	HEX	A2	A1	A0
24	0x18	0	0	0
25	0x19	0	0	1
26	0x1A	0	1	0
27	0x1B	0	1	1
28	0x1C	1	0	0
29	0x1D	1	0	1
30	0x1E	1	1	0
31	0x1F	1	1	1

On request manufacturer will provide 1001xxx as base address allowing up to 16 temp sensors on one bus.

Temperature and status

• setOffset(float offset) set an offset to calibrate or to correct for self heating. The value of offset is not validated to keep footprint small.
• getOffset() return value of offset (default 0);
• getTemperature() read the ambient temperature.
• getStatus() returns the status bits of the last call to getTemperature()

The value returned by getStatus() is the last value read by the call to GetTemperature(). There are three bits, see table below. A value of 6 means that TA is above the upper and above the critical temp.

Bit	Mask	Description	Notes
0	0x01	TA < TLOWER	lower
1	0x02	TA > TUPPER	larger
2	0x04	TA ≥ TCRIT	larger or equal

Resolution

• setResolution(uint8_t res) set the resolution, if res > 3, it is not set.
• getResolution() returns the resolution set

Value	Resolution	Conv time (ms)	Samples/s	Notes
0	0.5°C	30	33
1	0.25°C	65	15
2	0.125°C	130	7
3	0.0625°C	250	4	default

Config

• setConfigRegister(uint16_t cfg)
• getConfigRegister()

Bit	Mask	Name	Description	Value
0	0x0001	ALT MOD	alert mode	0 = comparator output, 1 = interrupt output
1	0x0002	ALT POL	alert polarity	0 = active low, 1 = active high
2	0x0004	ALT SEL	alert select	0 = upper+lower+crit, 1 = crit only
3	0x0008	ALT CNT	alert control	0 = OFF, 1 = ON
4	0x0010	ALT STAT	alert status	0 = OFF, 1 = ON (read!)
5	0x0020	INT CLR	interrupt clear	0 = none, 1 = clear interrupt
6	0x0040	WIN LOC	lock Tup + Tlow	0 = unlocked, 1 = Lock
7	0x0080	CRT LOC	lock Tcritical	0 = unlocked, 1 = Lock
8	0x0100	SHDN	shutdown,	0 = continuous mode, 1 = low power
9-10	0x0600	Hysteresis	Thysteresis	00 = 0°C, 01 = 1.5°C, 10 = 3°C, 11 = 6°C
11-15		always 0

Check datasheet for the details...

Temperature limits / thresholds

• setTupper(float temp) write upper register, accuracy 0.25°C
• getTupper() idem
• setTlower(float temp) write lower register, accuracy 0.25°C
• getTlower() idem
• setTcritical(float temp) write critical register, accuracy 0.25°C
• getTcritical() idem

The values written in these registers, are the trigger values for the status read with getStatus. Note that the Hysteresis temperature delta affects the value of these triggers.

The values set are not validated to keep footprint small.

Miscelaneous

• getManufacturerID() returns 84 (my version)
• getDeviceID() returns 0 (my version)
• getRevision() returns 84 (my version)
• getRFU() returns 29 (my version). Reserved for future use.

Hidden registers

The MCP9808 has hidden registers mentioned only on p.16 of the datasheet. These are for testing and calibration. The library prevents reading / writing them to keep sensors working.

Operation

See examples