esp-idf/examples/peripherals/rmt/onewire/README.md

Supported Targets	ESP32	ESP32-C3	ESP32-S2	ESP32-S3

Advanced RMT Transmit & Receive Example -- Simulate 1-Wire Bus

(See the README.md file in the upper level 'examples' directory for more information about examples.)

RMT peripheral has independent transmit and receive channels. We can simulate the 1-Wire bus by attaching a pair of transmit and receive channel to the same GPIO, and turning on the open-drain mode of the GPIO pad.

We've made the 1-Wire protocol implementation into a component called onewire_bus, which has been uploaded to the component registry.

This example demonstrates how to use that onewire_bus library to read temperature from the DS18B20 sensor. Likewise, the DS18B20 device is also made as a single component and pushed to the component registry.

One of the amazing feature that offered by the onewire_bus driver is that, is can support enumerate the devices on the bus, thus you can connect multiple DS18B20 sensors to the same bus and read their temperature one by one.

How to Use Example

Hardware Required

• A development board with any supported Espressif SOC chip (see Supported Targets table above)
• One or more DS18B20 sensors connected to the same bus by a 4.7 KΩ pull-up resistor

Connection :

┌──────────────────────────┐
│                      3.3V├───────┬─────────────┬──────────────────────┐
│                          │      ┌┴┐            │VDD                   │VDD
│          ESP Board       │  4.7k│ │     ┌──────┴──────┐        ┌──────┴──────┐
│                          │      └┬┘   DQ│             │      DQ│             │
│          ONEWIRE_GPIO_PIN├───────┴──┬───┤   DS18B20   │    ┌───┤   DS18B20   │   ......
│                          │          └───│-------------│────┴───│-------------│──
│                          │              └──────┬──────┘        └──────┬──────┘
│                          │                     │GND                   │GND
│                       GND├─────────────────────┴──────────────────────┘
└──────────────────────────┘

The GPIO number used in this example can be changed according to your board, by the macro EXAMPLE_ONEWIRE_BUS_GPIO defined in onewire_example_main.c.

Note

Parasite power mode is not supported, you have to connect VDD pin to make DS18B20 functional.

Build and Flash

Run idf.py -p PORT flash monitor to build, flash and monitor the project.

(To exit the serial monitor, type Ctrl-].)

See the Getting Started Guide for full steps to configure and use ESP-IDF to build projects.

Console Output

I (340) main_task: Started on CPU0
I (350) main_task: Calling app_main()
I (350) gpio: GPIO[0]| InputEn: 1| OutputEn: 0| OpenDrain: 0| Pullup: 1| Pulldown: 0| Intr:0
I (360) gpio: GPIO[0]| InputEn: 1| OutputEn: 1| OpenDrain: 1| Pullup: 1| Pulldown: 0| Intr:0
I (370) example: 1-Wire bus installed on GPIO0
I (370) example: Device iterator created, start searching...
I (490) example: Found a DS18B20[0], address: 070822502019FC28
I (590) example: Found a DS18B20[1], address: FC0921C076034628
I (590) example: Searching done, 2 DS18B20 device(s) found
I (1620) example: temperature read from DS18B20[0]: 22.50C
I (2430) example: temperature read from DS18B20[1]: 22.81C
I (3440) example: temperature read from DS18B20[0]: 22.50C
I (4250) example: temperature read from DS18B20[1]: 22.81C
I (5260) example: temperature read from DS18B20[0]: 22.50C
I (6070) example: temperature read from DS18B20[1]: 22.81C

Troubleshooting

For any technical queries, please open an issue on GitHub. We will get back to you soon.