Espressif Systems ESP Faq page 100

Chapter 4. Software framework
How to dynamically change the serial baud rate and make it take effect immediately with ESP32?
Please use the API uart_set_baudrate() to change the baud rate of UART. Please see
Reference.
Does the ESP32 chip support USRAT (Universal Synchronous Asynchronous Receiver Transmitter)?
It's not support. ESP32 only supports UART and cannot provide the synchronous clock.
Does the serial port verification of the ESP32 chip support MARK and SPACE verification?
No.
What is the size of the hardware FIFO in ESP8266's serial port?
Both UART0 and UART1 of ESP8266 have a 128-byte hardware FIFO and a 128-byte RW FIFO, which
operate at the same address. Please refer to Section 11.2. Hardware Resources in
Reference Manual.
What is the serial port baud rate range of ESP8266?
300 ~ 115200*40 bps. Please refer to Section 11.3.1. Baud Rate in
Manual.
How to modify the output port of UART0?
CHIP: ESP32 | ESP32 | ESP32-C3
This can be set in menuconfig: idf.py menuconfig —> Component config —> Common
ESP-related -> Channel for console output(custom UART).
When using ESP8266, I want to use UART0 exclusively for downloading, and then use UART1 to communi-
cate with other chips. Can GPIO4 and GPIO5 be configured as UART1 serial ports?
• Since the RXD of UART1 is occupied, UART1 cannot be used to communicate with other chips, but the TXD
pin of UART1 can be used to output logs.
• ESP8266 can only communicate with other chips by swapping CTS and RTS pins of UART0. It will be invalid
to configure GPIO4 and GPIO5.
• ESP8266 can communicate with other chips by calling"uart_enable_swap()"to swap the CTS and RTS pins
of UART0 to MTCK (IO13) and MTDO (IO15). After this, ESP8266 can communicate with other chips via
GPIO13 (TXD) and GPIO15 (RXD).
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