Baud speed of UART.

[ESP_Alen]

The designed frequency of crystal oscillator used by ESP8266 is 40MHz, but it is replaced with crystal oscillator of 26MHz.
So the default baud speed of UART is 74880.

if the frequency of crystal oscillator is 40MHz, the baud speed of UART is 115200.

You can configure the baud ratio to modify UART_BAUD_RATIO in user_config.h
now, the default baud is 74880.