ESP8266_RTOS_SDK/examples/peripherals/uart_echo

UART Echo Example

This is an example which echoes any data it receives on UART0 back to the sender.

How to use example

Hardware Required

1. Connect an external serial interface to an ESP8266 board. The external interface should have 3.3V outputs. You may use e.g. 3.3V compatible USB-to-serial dongle:

ESP8266 Interface	#define	ESP8266 Pin	External UART Pin
Transmit Data (TxD)	ECHO_TEST_TXD	GPIO26	RxD
Receive Data (RxD)	ECHO_TEST_RXD	GPIO25	TxD
Ground	n/a	GND	GND

2. Verify if echo indeed comes from ESP8266 by disconnecting either 'TxD' or 'RxD' pin. There should be no any echo once any pin is disconnected.

• Using a hardware flow control

  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.

  1. Connect the extra RTS/CTS signals as below

     ESP8266 Interface	#define	ESP8266 Pin	External UART Pin
     Request to Send (RTS)	ECHO_TEST_RTS	GPIO13	CTS
     Clear to Send (CTS)	ECHO_TEST_CTS	GPIO12	RTS

  2. Configure UART0 driver to use the hardware flow control by setting .flow_ctrl = UART_HW_FLOWCTRL_CTS_RTS and adding .rx_flow_ctrl_thresh = 122

Configure the project

make menuconfig

• Set serial port under Serial Flasher Options.
• make monitor baud rate set to what you set in the example.

Build and Flash

Build the project and flash it to the board, then run monitor tool to view serial output:

make -j4 flash monitor

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

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

Example Output

I (180) boot: Loaded app from partition at offset 0x10000
I (0) system_api: Base MAC address is not set, read default base MAC address from BLK0 of EFUSE
I (0) system_api: Base MAC address is not set, read default base MAC address from BLK0 of EFUSE
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