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74 lines
2.4 KiB
Markdown
74 lines
2.4 KiB
Markdown
# UART Echo Example
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(See the README.md file in the upper level 'examples' directory for more information about examples.)
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This example demonstrates how to utilize UART interfaces of ESP32 by echoing back to the sender any data received on
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UART1.
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## How to use example
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### Hardware Required
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The example can be run on any ESP32 development board connected to a PC with a single USB cable for flashing and
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monitoring. The external interface should have 3.3V outputs. You may use e.g. 3.3V compatible USB-to-Serial dongle.
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### Setup the Hardware
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Connect the external serial interface to the ESP32 board as follows.
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| ESP32 Interface | #define | ESP32 Pin | External UART Pin |
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| --- | --- | --- | --- |
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| Transmit Data (TxD) | ECHO_TEST_TXD | GPIO4 | RxD |
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| Receive Data (RxD) | ECHO_TEST_RXD | GPIO5 | TxD |
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| Ground | n/a | GND | GND |
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Optionally, you can set-up and use a serial interface that has RTS and CTS signals in order to verify that the
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hardware control flow works. Connect the extra signals according to the following table, configure both extra pins in
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the example code by replacing existing `UART_PIN_NO_CHANGE` macros with the appropriate pin numbers and configure
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UART1 driver to use the hardware flow control by setting `.flow_ctrl = UART_HW_FLOWCTRL_CTS_RTS` and adding
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`.rx_flow_ctrl_thresh = 122`.
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| ESP32 Interface | #define | ESP32 Pin | External UART Pin |
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| --- | --- | --- | --- |
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| Request to Send (RTS) | ECHO_TEST_RTS | GPIO18 | CTS |
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| Clear to Send (CTS) | ECHO_TEST_CTS | GPIO19 | RTS |
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### Configure the project
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```
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idf.py menuconfig
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```
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or
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```
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idf.py menuconfig
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```
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* Set serial port under Serial Flasher Options.
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### Build and Flash
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Build the project and flash it to the board, then run monitor tool to view serial output:
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```
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idf.py -p PORT flash monitor
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```
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or
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```
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idf.py -p PORT flash monitor
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```
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(To exit the serial monitor, type ``Ctrl-]``.)
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See the Getting Started Guide for full steps to configure and use ESP-IDF to build projects.
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## Example Output
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Type some characters in the terminal connected to the external serial interface. As result you should see echo in the
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terminal which is used for flashing and monitoring. You can verify if the echo indeed comes from ESP32 by
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disconnecting either `TxD` or `RxD` pin: no characters will appear when typing.
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## Troubleshooting
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You are not supposed to see the echo in the terminal which is used for flashing and monitoring, but in the other one
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which is connected to UART1.
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