dzsoni/nonblockingdallas

Arduino library for the DS18B20 temperature sensor. Avoid blocking the sketch while reading the sensor.

Non blocking temperature sensor library for Arduino

This simple library for Arduino implements a machine state for reading the Maxim Integrated DS18B20 temperature sensor without blocking the main loop() of the sketch. It is designed for a continuos sensor reading every amount of time configurable by the developer. It is also possible to request a new sensor reading on the fly by calling the requestTemperature() function.

While the conversion is in progress, the main loop() continues to run so that the sketch can execute other tasks. When the temperature reading is ready, a callback is invoked. At full resolution the conversion time takes up to 750 milliseconds, a huge amount of time, thus the importance of the library to avoid blocking the sketch execution.

Features

Supports up to 15 sensors on the same ONE WIRE bus. To get some debug information, simply remove the comment on following line in NonBlockingDallas.h:

#define DEBUG_DS18B20

The output will be like the following:

DS18B20: 3 sensors found on the bus
DS18B20: parasite power is OFF
DS18B20: requested new reading
DS18B20 (0): 29.37 °C
DS18B20 (1): 29.12 °C
DS18B20 (2): 29.26 °C
DS18B20: requested new reading
DS18B20 (0): 29.37 °C
DS18B20 (1): 29.12 °C
DS18B20 (2): 29.26 °C
...

Callbacks

The library is callback driven: onIntervalElapsed is invoked every time the timer interval is elapsed, onTemperatureChange is invoked only when the temperature value changes between two sensor readings. Both of them provide the temperature, a bool value which indicates wether the readout is valid and the sensor index from 0 to 14.

void onIntervalElapsed(void(*callback)(float temperature, bool valid, int deviceIndex)) {
	cb_onIntervalElapsed = callback;
}

void onTemperatureChange(void(*callback)(float temperature, bool valid, int deviceIndex)) {
	cb_onTemperatureChange = callback;
}

Sensor Resolution

The conversion time of the DS18B20 temperature sensor depends on its resolution, thus the time interval parameter passed to the begin function must be greater than or equal to the conversion time.

Resolution	Conversion time
9 bit	93 ms
10 bit	187 ms
11 bit	375 ms
12 bit	750 ms

Prerequisites

This library uses OneWire and DallasTemperature libraries, so you will need to have those installed.

Installation

The library is available from the Arduino Library Manager: load the Arduino IDE, then use the menu at the top to select Sketch -> Include Library -> Manage Libraries. Type NonBlockingDallas in the search box.

Click the following badge for a complete installation guide

Usage

Step 1

Include the required libraries:

#include <OneWire.h>
#include <DallasTemperature.h>
#include <NonBlockingDallas.h>

Step 2

Create the instance of the classes:

OneWire oneWire(ONE_WIRE_BUS);
DallasTemperature dallasTemp(&oneWire);
NonBlockingDallas sensorDs18b20(&dallasTemp);

Step 3

Initialize the sensor and set the callbacks. The parameters of the begin function are the sensor resolution, unit of measure (Celsius or Fahrenheit) and time interval in milliseconds.

sensorDs18b20.begin(NonBlockingDallas::resolution_12, NonBlockingDallas::unit_C, 1500);

Possible values are:

• resolution_9

• resolution_10

• resolution_11

• resolution_12

• unit_C for degrees Celsius

• unit_F for Fahrenheit

Step 4

Implement the callbacks' functions and call the update function inside the main loop()

void loop() {
 sensorDs18b20.update();
}

void handleIntervalElapsed(float temperature, bool valid, int deviceIndex){

}

void handleTemperatureChange(float temperature, bool valid, int deviceIndex){

}

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Please see the Example for a complete working sketch