37 lines
1.8 KiB
Markdown
37 lines
1.8 KiB
Markdown
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# UART Echo Example
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This is an example which echoes any data it receives on UART1 back to the sender.
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## Setup
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1. Connect an external serial interface to an ESP32 board. The external interface should have 3.3V outputs. You may use e.g. 3.3V compatible USB-to-serial dongle:
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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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2. Compile and load the example to the ESP32 board
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3. Refer to the example and set up a serial terminal program to the same settings as of UART1 in ESP32
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4. Open the external serial interface in the terminal
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5. When typing any character in the terminal you should see it echoed back
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6. Verify if echo indeed comes from ESP32 by disconnecting either 'TxD' or 'RxD' pin. There should be no any echo once any pin is disconnected.
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## Using a hardware flow control
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This is an optional check to verify if the hardware flow control works. To set it up you need an external serial interface that has RTS and CTS signals.
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1. Connect the extra RTS/CTS signals as below
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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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2. Configure both extra pins in the example code by replacing existing `UART_PIN_NO_CHANGE` macros with the above pin numbers
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3. Configure UART1 driver to use the hardware flow control by setting `.flow_ctrl = UART_HW_FLOWCTRL_CTS_RTS` and adding `.rx_flow_ctrl_thresh = 122`
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4. Repeat tests described in 'Setup' above starting from step 3
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See the README.md file in the upper level 'examples' directory for more information about examples.
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