This Arduino sketch lists the addresses of all DS18x and DS2x temperature sensors on a single bus (via the 1-Wire serial protocol), fetches their addresses (to be more precise: Their unique 64 bit ID) and outputs their temperature readings to the specified serial port in degree Celsius and Fahrenheit.
This sketch can be used to check the functionality of a circuit or to list the hardware addresses of the hooked up temperature sensors.
The unique and unchangeable 64-bit ID of a 1-wire device consists of a 48-bit serial number, an 8-bit family code and an 8-bit CRC checksum. The ID is used to communicate with a 1-wire device on the bus and must be unique.
Example of a 64-bit 1-wire device id:
0x10 0x01 0xCB 0xC2 0x02 0x07 0x00 0x99
- 0x10: Stands for the device family code (See below)
- 0x01 0xCB 0xC2 0x02 0x07 0x00: Represents the serial number
- 0x99: 8-bit CRC checksum
| Temperature Sensor | Device family code | Additional Info |
|---|---|---|
| DS18S20 MODEL | 0x10 | also DS1820 |
| DS18B20 MODEL | 0x28 | also MAX31820 |
| DS1822 MODEL | 0x22 | |
| DS1825 MODEL | 0x3B | |
| DS28EA00 MODEL | 0x42 |
Wiring diagram of one DS1820 temperature sensor. The sensor can be operated in normal mode or parasite mode. In parasite mode the sensor gets its energy from the data line (which is connected to VCC [3.3V or 5V]) when no data is transmitted. The energy is stored in a small capacitor inside the sensor and is used for the next data transmission.
If you need additional help with wiring check out this site: How to interface multiple DS18B20 on a single bus
Both libraries can be installed through the Arduino IDE.
- Go to Tools -> Manage libraries...
- Search for: OneWire
- Install version 2.3.5 or above
- Search for: DallasTemperature
- Install version 3.8.0 or above
- Your sensors are wired correctly as expected by the 1-wire bus system (Normal power mode or parasite power mode)
- Your circuit is hooked up to an Arduino board on Digital Input/Output PIN2
- Connect: GND <-> GND, DATA <-> PIN2, VCC <-> 3,3V or 5V.
- You are using one pull up resistor (4.7k ohm) between Data and VCC to be able to read from the sensors etc.
- This sketch is functional but has not been thoroughly tested
- It is suitable for demonstration purposes only
- It might find all different types of 1-wire sensors on the line but can deal with temperature sensors only
- The code only finds a maximum number of sensors which is defined by MAX_NUMBER_OF_POSSIBLE_SENSORS_FOUND
- ...but that's not problem because you can set the number as high as you want. Restricted only by the amount of available memory for globals.
- Because the code was written for demonstration purposes it is very verbose and unoptimized
- Perform basic setup
- Get the number of devices on the bus
- Check if the sensors are running in parasite mode
- Search for 1-wire devices on the bus and get their addresses
- Populate the array with the addresses [temp_sensors]
- Set the precision of the sensors [TEMPERATURE_PRECISION]
- |--> Perform sensor readings and get the results in degree Celsius and Fahrenheit
- | Iterate over all sensors and print the addresses and temperature readings
- | Pause for a few seconds
- |-- Repeat
To avoid dynamic memory allocation, a preprocessor variable: MAX_NUMBER_OF_POSSIBLE_SENSORS_FOUND is used to specify the maximum number of discoverable sensors. This integer is used to statically allocated the needed memory (globals) for the array (temp_sensors) that stores the address of each sensor.
However, this approach limits the number of devices that can be found by the script. It's a little ugly but does the job. You will need 8 bytes of global memory to store a single device address.
eg: MAX_NUMBER_OF_POSSIBLE_SENSORS_FOUND = 10 -> max. 10 discoverable sensors * 8 bytes for each sensor = 80 bytes in total.
You can change MAX_NUMBER_OF_POSSIBLE_SENSORS_FOUND to any integer that is suitable for your project as long as you have enough (global) RAM and as long as it's bigger or equal than the actual number of physical devices hooked up on the bus.
DS1820 and DS18S20 have no 'resolution configuration register'. This means, they don't support resolution changes via the setResolution() call of the library. In this sketch the resolution change is used anyway for all sensor models without differentiation because it does not seem to have any effects on the sensors that don't support it.
This example uses source code from the DallasTemperature library.
The sketch displays all temperature sensors and their addresss and outputs their temperature readings in Celsius and Fahrenheit.
Dallas DS18x and DS2x temperature sensor example Number of sensors found: 3 Parasite power is: ON Sensor found with address: 0x10 0x1 0xCB 0xC2 0x2 0x8 0x0 0x99 Setting resolution for sensor: 1001CBC202080099 to: 12 bit Getting resolution for sensor 1001CBC202080099: 12 bit Sensor found with address: 0x10 0xCB 0x61 0xDE 0x2 0x8 0x0 0x6D Setting resolution for sensor: 10CB61DE0208006D to: 12 bit Getting resolution for sensor 10CB61DE0208006D: 12 bit Sensor found with address: 0x10 0x9B 0xDA 0xDE 0x2 0x8 0x0 0x7C Setting resolution for sensor: 109BDADE0208007C to: 12 bit Getting resolution for sensor 109BDADE0208007C: 12 bit Sensor: 0 @1001CBC202080099 Temperatur: 24.50°C Temperatur: 76.10°F Sensor: 1 @10CB61DE0208006D Temperatur: 25.31°C Temperatur: 77.56°F Sensor: 2 @109BDADE0208007C Temperatur: 24.31°C Temperatur: 75.76°F
If you found bugs or/and put extra work into the sketch, please contribute so that others can benefit and learn from it.
Thank you.