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11. UART Introduction

11.

UART Introduction

11.1. Functional Overview

There are two group ESP8266 UART interfaces, respectively:

•

UART0:

- U0TXD: pin26 (U0TXD)

- U0RXD: pin25 (U0RXD)

- U0CTS: pin12 (MTCK)

- U0RTS: pin13 (MTDO)

•

UART1:

- U1TXD: pin14 (GPIO2)

The basic working process of transmission FIFO:

As long as there has data ﬁlling into transmission FIFO, it will immediately start sending

process.Since transmission itself is a relatively slow process,other data can be sent to the

transmission FIFO simultaneously. Data sending should be paused when the transmission

FIFO is full ,or it will cause data loss.Transmission FIFO will sent out one by one in

accordance with the order of the data ﬁlling in,until the transmission FIFO is completely

empty.Data has been sent will be automatically cleared, at the same time transmission FIFO

will be more of a vacancy.

The basic working process of receiver FIFO:

When the hardware logic receives the data, it will ﬁll them into receiver FIFO. Program

should withdraw the data timely ,the data-dequeue is also a process of deleting data from

FIFO automatically,thus, there will be one more vacancy in receiver FIFO. If the data in the

receiver FIFO can not be removed in time, the receiver FIFO will be full which makes data

loss.

Scenario:

UART0 works as data communication interface and UART1 woks as debug port.

Espressif

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2017.05

ESP8266 Datasheet(PDF) 86 Page - ESPRESSIF SYSTEMS (SHANGHAI) CO., LTD.