Example Code for Arduino-Comparator Mode
Get the status of comparing the current temperature with the upper limit, lower limit and critical value.
Hardware Preparation
- DFRduino UNO R3 x 1
- MCP9808 High Accuracy Digital Temperature Sensor x 1
- Jumper wires
Software Preparation
- Arduino IDE
- Download and install the MCP9808 Library and Sample Program. (About how to install the library?)
Wiring Diagram
Other Preparation Work
- Connect the sensor to the Arduino as per the wiring diagram.
- Open Arduino IDE and load the sample code.
- Select the correct board and port in Arduino IDE.
Sample Code
/*!
* @file comparatorMode.ino
* @brief Get the status of comparing the current temp with the upper/lower limit and threshold.
* @details Experimental phenomenon: display temp and comparison status on the serial port
* @details Experimental phenomenon: when the temp is above the upper limit, pin ALE level will switch,
* @details Experimental phenomenon: when the temp is below the lower limit, pin ALE level will switch,
* @details Experimental phenomenon: when the temp is above the critical temp, pin ALE level will switch,
* @copyright Copyright (c) 2010 DFRobot Co.Ltd (http://www.dfrobot.com)
* @license The MIT License (MIT)
* @author ZhixinLiu([email protected])
* @version V1.0
* @date 2021-04-16
* @url https://github.com/DFRobot/DFRobot_MCP9808
*/
#include "DFRobot_MCP9808.h"
/**
* i2c address select, default to be MCP9808_ADDRESS_7, pin A2, A1 and A0 is at high level
* 1 for high level, 0 for low level, | A2 | A1 | A0 |
* MCP9808_ADDRESS_0 | 0 | 0 | 0 | 0x18
* MCP9808_ADDRESS_1 | 0 | 0 | 1 | 0x19
* MCP9808_ADDRESS_2 | 0 | 1 | 0 | 0x1A
* MCP9808_ADDRESS_3 | 0 | 1 | 1 | 0x1B
* MCP9808_ADDRESS_4 | 1 | 0 | 0 | 0x1D
* MCP9808_ADDRESS_5 | 1 | 0 | 1 | 0x1D
* MCP9808_ADDRESS_6 | 1 | 1 | 0 | 0x1E
* MCP9808_ADDRESS_7 | 1 | 1 | 1 | 0x1F
*/
#define I2C_ADDRESS MCP9808_ADDRESS_7
DFRobot_MCP9808_I2C mcp9808(&Wire, I2C_ADDRESS);
void setup()
{
Serial.begin(115200);
while(!Serial);
while(!mcp9808.begin()){
Serial.println("begin failed!");
delay(1000);
} Serial.println("begin success!");
/**
* Wake up sensor, sensor data can be obtained normally at this time
*/
if(!mcp9808.wakeUpMode()){
Serial.println("Register locked, Please unlock!");
}else{
Serial.println("Wake up sensor successfully, can read the temperature!");
}
/**
* Set temp resolution
* RESOLUTION_0_5 The decimal part of the obtained temp is a multiple of 0.5 e.g. 0.5°C, 1.0°C, 1.5°C
* RESOLUTION_0_25 The decimal part of the obtained temp is a multiple of 0.25 e.g. 0.25°C, 0.50°C, 0.75°C
* RESOLUTION_0_125 The decimal part of the obtained temp is a multiple of 0.125 e.g. 0.125°C, 0.250°C, 0.375°C
* RESOLUTION_0_0625 The decimal part of the obtained temp is a multiple of 0.0625 e.g. 0.0625°C, 0.1250°C, 0.1875°C
*/
if(mcp9808.setResolution(RESOLUTION_0_25)){
Serial.println("Set temp resolution successfully!");
}else{
Serial.println("parameter error!");
}
/**
* Set alert output mode, clearing interrupt is not required in comparator output mode, but required in interrupt mode
* COMPARATOR_OUTPUT_MODE clearing interrupt is not required in comparator output mode,
* For example: set pin ALE to be active on low, when the temp exceeds the upper limit alert temp, pin ALE level turns from high to low; when it's below the upper but above the lower limit, pin ALE level turns back to high
* INTERRPUT_OUTPUT_MODE clearing interrupt is required in interrupt mode, when an alert occurs, the interrupt keep existing if it's not cleared, triggering interrupt mode indicates changing status.
* For example, set lower threshold to be 20 degrees, upper threshold 25°C, and threshold 30°C, no interrupt occurs when temp is below 20°C; when temp exceeds 25°C, interrupt occurs and pin ALE jump, the interrupt should be cleared at the time and pin ALE is restored;
* in the special case, when current temp is above the critical temp of 30°C, the interrupt mode and clearing interrupt are both invalid, the interrupt mode will be restored only when the temp drops below 30°C.
* DISABLE_OUTPUT_MODE After disabling output mode, no alert occurs and pin ALE is invalid
*/
if(mcp9808.setAlertOutputMode(COMPARATOR_OUTPUT_MODE) == 0){
Serial.println("Set alert output mode successfully!");
}else{
Serial.println("Register locked or parameter error!");
}
/**
* Set pin ALE polarity, high polarity: pin ALE is active on high, the default is low level, which turns to high when alert occurs.
* low polarity: pin ALE is active on low, the default is high level, which turns to low when alert occurs.
* POLARITY_HIGH pin ALE is active on high
* POLARITY_LOW pin ALE is active on low
*/
if(mcp9808.setPolarity(POLARITY_LOW) == 0){
Serial.println("Set pin ALE polarity successfully!");
}else{
Serial.println("Register locked or parameter error!");
}
/**
* Set alert response mode, respond to upper & lower limits and threshold; or only respond to threshold, which is inapplicable to interrupt mode
* UPPER_LOWER_CRIT_RESPONSE respond to upper/lower limits and threshold
* ONLY_CRIT_RESPONSE disable upper/lower limits response, only respond to threshold
*/
if(mcp9808.setAlertResponseMode(UPPER_LOWER_CRIT_RESPONSE) == 0){
Serial.println("Set response mode successfully!");
}else{
Serial.println("Register locked or parameter error!");
}
/**
* Set threshold value, the upper and lower thresholds, and respond according to the configured interrupt mode, responding interruption when the temp is above the upper limit, below the lower limit and above the threshold
* crit: Temp threshold, up to two decimal places, automatically processed to multiples of 0.25, range is from -40 to +125°C
* upper: Upper limit temp, up to two decimal places, automatically processed to multiples of 0.25, range is from -40 to +125°C
* lower: Lower limit temp, up to two decimal places, automatically processed to multiples of 0.25, range is from -40 to +125°C
*/
if(mcp9808.setThreshold(/*crit*/35.0, /*upper*/30.0, /*lower*/20.0) == 0){
Serial.println("Set temp of threshold, upper and lower limit successfully!");
}else{
Serial.println("Register locked or data error");
}
/**
* Set alert temp hysteresis range, add a range to the upper limit, lower limit and threshold, hysteresis function is only applicable to reduce temperature (from hot to cold)
* i.e, ALE level will be restored only when the temp reaches the value obtained by subtracting hysteresis temp from the upper limit.
* For example: maximum temp is 30.0°C, hysteresis temp is +1.5°C, the current temp is 35°C and ALE level has flipped,
* the temp must reach 30-1.5=28.5°C before restoring ALE level
* HYSTERESIS_0_0 No hysteresis, respond when reaching the specified temp
* HYSTERESIS_1_5 1.5℃ lag from hot to cold
* HYSTERESIS_3_0 3.0℃ lag from hot to cold
* HYSTERESIS_6_0 6.0℃ lag from hot to cold
*/
if(mcp9808.setAlertHysteresis(HYSTERESIS_1_5) == 0){
Serial.println("Set temp hysteresis successfully!");
}else{
Serial.println("Register locked or parameter error!");
}
/**
* Set lock mode or unlock, prevent wrong operations that may change upper limit, lower limit and threshold value,
* and unlock only by power-off reset after locking
* CRIT_LOCK Lock threshold value, which is not allowed to be changed
* WIN_LOCK Lock upper and lower thresholds, which are not allowed to be changed
* CRIT_WIN_LOCK Lock threshold value, upper and lower limit, which are not allowed to be changed
* NO_LOCK No locking of threshold value, upper and lower limit
*/
if(mcp9808.setLockState(NO_LOCK)){
Serial.println("Set locking mode successfully!");
}else{
Serial.println("parameter error!");
}
}
void loop()
{
/**
* Get the current comparator status and temp data, which works only in comparator mode
* Struct storing the current data
* temperate Current temp
* state Character string of the comparator status, compare the current temp with the upper threshold, lower threshold, and threshold value
*/
sComparator_t data = mcp9808.getComparatorState();
Serial.print("temperature = ");
Serial.print(data.temperature);
Serial.println(" C");
Serial.print("state is ");
Serial.println(data.state);
delay(1000);
// if(mcp9808.sleepMode()){ Serial.println("sleep sensor success!");} // Sensor enter sleep mode, fail to get the correct temp in sleep mode
}
Result
The temperature and the comparing status will be displayed on the serial port. When the temperature beyond the upper limit, ALE pin level will reverse; when the temperature below the lower limit, ALE pin level will reverse; when the temperature beyond the critical temperature, ALE pin level will reverse.
Was this article helpful?