esp32-ds18b20-example

Introduction

This is an example application for the Maxim Integrated DS18B20 Programmable Resolution 1-Wire Digital Thermometer device.

It supports a single or multiple devices on the same 1-Wire bus.

It is written and tested for v3.3 and v4.1-beta1 of the ESP-IDF environment, using the xtensa-esp32-elf toolchain (gcc version 5.2.0, crosstool-ng-1.22.0-80-g6c4433a).

Ensure that submodules are cloned:

$ git clone --recursive https://github.com/DavidAntliff/esp32-ds18b20-example.git

Build the application with:

$ cd esp32-ds18b20-example
$ idf.py menuconfig    # set your serial configuration and the 1-Wire GPIO - see below
$ idf.py build
$ idf.py -p (PORT) flash monitor

The program should detect your connected devices and periodically obtain temperature readings from them, displaying them on the console.

Dependencies

This application makes use of the following components (included as submodules):

components/esp32-owb
components/esp32-ds18b20

Hardware

To run this example, connect one or more DS18B20 devices to a single GPIO on the ESP32. Use the recommended pull-up resistor of 4.7 KOhms, connected to the 3.3V supply.

idf.py menuconfig can be used to set the 1-Wire GPIO.

If you have several devices and see occasional CRC errors, consider using a 2.2 kOhm pull-up resistor instead. Also consider adding decoupling capacitors between the sensor supply voltage and ground, as close to each sensor as possible.

If you wish to enable a second GPIO to control an external strong pull-up circuit for parasitic power mode, ensure CONFIG_ENABLE_STRONG_PULLUP=y and CONFIG_STRONG_PULLUP_GPIO is set appropriately.

See documentation for esp32-ds18b20 for further information about parasitic power mode, including strong pull-up configuration.

Features

This example provides:

External power supply detection.
Parasitic power supply detection.
Static (stack-based) or dynamic (malloc-based) memory model examples.
No global variables.
Device search.
Addressing optimisation for a single (solo) device on a bus.
CRC checks on ROM code and temperature data.
Programmable temperature measurement resolution (9, 10, 11 or 12-bit resolution).
Temperature conversion and retrieval.
Simultaneous conversion across multiple devices.

Source Code

The source is available from GitHub.

License

The code in this project is licensed under the MIT license - see LICENSE for details.

Acknowledgements

"1-Wire" is a registered trademark of Maxim Integrated.

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