OK we are now going to look at an MCP9808 attached to the STM32 Nucleo and all development will be done on the Arduino IDE – Install STM32 support in the Arduino IDE
The MCP9808 digital temperature sensor converts temperatures between -20°C and +100°C to a digital word with ±0.5°C (max.) accuracy. The MCP9808 comes with user-programmable registers that provide flexibility for temperature sensing applications. The registers allow user-selectable settings such as Shutdown or low-power modes and the specification of temperature Event and Critical output boundaries. When the temperature changes beyond the specified boundary limits, the MCP9808 outputs an Event signal.
The user has the option of setting the event output signal polarity as an active-low or active-high comparator output for thermostat operation, or as temperature event interrupt output for microprocessor-based systems. The event output can also be configured as a Critical temperature output.
This sensor has an industry standard 2-wire, SMBus and Standard I2C™Compatible compatible (100kHz/400kHz bus clock) serial interface, allowing up to eight sensors to be controlled in a single serial bus.
Features
Accuracy:
±0.25°C (typical) from -40°C to +125°C
±0.5°C (maximum) from -20°C to +100°C
User Selectable Measurement Resolution:
0.5°C, 0.25°C, 0.125°C, 0.0625°C
User Programmable Temperature Limits:
Temperature Window Limit
Critical Temperature Limit
User Programmable Temperature Alert Output
Operating Voltage Range: 2.7V to 5.5V
More details about the sensor at http://www.microchip.com/wwwproducts/en/MCP9808
Connection
stm32 and mcp9808
Code
You will need the adafruit MCP9808 library which is available at https://github.com/adafruit/Adafruit_MCP9808_Library/archive/master.zip
[codesyntax lang=”cpp”]
#include <Wire.h>
#include "Adafruit_MCP9808.h"
// Create the MCP9808 temperature sensor object
Adafruit_MCP9808 tempsensor = Adafruit_MCP9808();
void setup() {
Serial.begin(9600);
if (!tempsensor.begin())
{
Serial.println("Couldn't find MCP9808!");
while (1);
}
}
void loop() {
// Read and print out the temperature, then convert to *F
float c = tempsensor.readTempC();
float f = c * 9.0 / 5.0 + 32;
Serial.print("Temp: ");
Serial.print(c);
Serial.print(" C\t");
Serial.print(f);
Serial.println(" F");
delay(250);
tempsensor.shutdown_wake(1);
delay(2000);
tempsensor.shutdown_wake(0);
}
[/codesyntax]
Results
Open the serial monitor and you should see something like this
Temp: 24.94 C 76.89 F
Temp: 27.50 C 81.50 F
Temp: 28.25 C 82.85 F
Temp: 27.44 C 81.39 F
Temp: 26.75 C 80.15 F
Temp: 26.50 C 79.70 F
Temp: 26.25 C 79.25 F
Temp: 26.06 C 78.91 F
Temp: 25.94 C 78.69 F
Temp: 25.75 C 78.35 F
Links
Adafruit MCP9808 High Accuracy I2C Temperature Sensor Breakout Board [ADA1782]