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91 lines
5.0 KiB
Markdown
91 lines
5.0 KiB
Markdown
| Supported Targets | ESP32 | ESP32-C3 | ESP32-C6 | ESP32-S2 | ESP32-S3 |
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| ----------------- | ----- | -------- | -------- | -------- | -------- |
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# RMT Transmit & Receive Example -- 1-Wire bus
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(See the README.md file in the upper level 'examples' directory for more information about examples.)
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RMT peripheral has both transmit and receive channels. Connecting one transmit channel and one receive channel to the same GPIO and put the GPIO in open-drain mode can simulate bi-directional single wire protocols, such as [1-Wire protocol](https://www.maximintegrated.com/en/design/technical-documents/tutorials/1/1796.html).
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This example demonstrates how to use RMT to simulate 1-Wire bus and read temperatrue from [DS18B20](https://datasheets.maximintegrated.com/en/ds/DS18B20.pdf).
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## How to Use Example
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### Hardware Required
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* A development board with any supported Espressif SOC chip (see `Supported Targets` table above)
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* Several DS18B20 temperature sensors and a 4.7kohm pullup resistor
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Connection :
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```
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┌──────────────────────────┐
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│ 3.3V├───────┬─────────────┬──────────────────────┐
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│ │ ┌┴┐ │VDD │VDD
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│ ESP32 Board │ 4.7k│ │ ┌──────┴──────┐ ┌──────┴──────┐
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│ │ └┬┘ DQ│ │ DQ│ │
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│ ONEWIRE_GPIO_PIN├───────┴──┬───┤ DS18B20 │ ┌───┤ DS18B20 │ ......
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│ │ └───│-------------│────┴───│-------------│──
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│ │ └──────┬──────┘ └──────┬──────┘
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│ │ │GND │GND
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│ GND├─────────────────────┴──────────────────────┘
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└──────────────────────────┘
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```
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The GPIO number used in this example can be changed according to your board, by the macro `EXAMPLE_ONEWIRE_GPIO_PIN` defined in [onewire_ds18b20_example_main.c](main/onewire_ds18b20_example_main.c).
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*Note*: Parasite power mode is not supported currently by this example, you have to connect VDD pin to make DS18B20 functional.
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### Build and Flash
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Run `idf.py -p PORT flash monitor` to build, flash and monitor the project.
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(To exit the serial monitor, type ``Ctrl-]``.)
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See the [Getting Started Guide](https://docs.espressif.com/projects/esp-idf/en/latest/get-started/index.html) for full steps to configure and use ESP-IDF to build projects.
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## Console Output
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If there are some DS18B20s on the bus:
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```
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I (327) cpu_start: Starting scheduler on PRO CPU.
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I (0) cpu_start: Starting scheduler on APP CPU.
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I (338) gpio: GPIO[5]| InputEn: 1| OutputEn: 0| OpenDrain: 0| Pullup: 1| Pulldown: 0| Intr:0
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I (348) onewire_rmt: RMT Tx channel created for 1-wire bus
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I (358) gpio: GPIO[5]| InputEn: 1| OutputEn: 1| OpenDrain: 1| Pullup: 1| Pulldown: 0| Intr:0
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I (358) onewire_rmt: RMT Rx channel created for 1-wire bus
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I (368) example: 1-wire bus installed
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I (418) example: found device with rom id 28FF30BE21170317
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I (458) example: found device with rom id 28FF297E211703A1
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I (498) example: found device with rom id 28FF6F7921170352
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I (508) example: 3 devices found on 1-wire bus
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I (2518) example: temperature of device 28FF30BE21170317: 27.00C
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I (2528) example: temperature of device 28FF297E211703A1: 26.81C
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I (2538) example: temperature of device 28FF6F7921170352: 26.50C
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I (3548) example: temperature of device 28FF30BE21170317: 26.94C
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I (3558) example: temperature of device 28FF297E211703A1: 26.75C
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I (3568) example: temperature of device 28FF6F7921170352: 26.44C
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```
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If there is no DS18B20 on the bus:
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```
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I (327) cpu_start: Starting scheduler on PRO CPU.
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I (0) cpu_start: Starting scheduler on APP CPU.
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I (337) gpio: GPIO[5]| InputEn: 1| OutputEn: 0| OpenDrain: 0| Pullup: 1| Pulldown: 0| Intr:0
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I (347) onewire_rmt: RMT Tx channel created for 1-wire bus
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I (357) gpio: GPIO[5]| InputEn: 1| OutputEn: 1| OpenDrain: 1| Pullup: 1| Pulldown: 0| Intr:0
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I (357) onewire_rmt: RMT Rx channel created for 1-wire bus
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I (367) example: 1-wire bus installed
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E (377) onewire_rmt: no device present on 1-wire bus
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I (377) example: 0 device found on 1-wire bus
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I (387) gpio: GPIO[5]| InputEn: 0| OutputEn: 0| OpenDrain: 0| Pullup: 1| Pulldown: 0| Intr:0
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I (397) gpio: GPIO[5]| InputEn: 0| OutputEn: 0| OpenDrain: 0| Pullup: 1| Pulldown: 0| Intr:0
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I (397) example: 1-wire bus deleted
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```
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## Troubleshooting
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For any technical queries, please open an [issue] (https://github.com/espressif/esp-idf/issues) on GitHub. We will get back to you soon.
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