ESP8266 datasheet(93/117 Pages) ESPRESSIF

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11. UART Introduction

Send empty ﬁfo interrupt

Interrupt status bit: UART_TXFIFO_EMPTY_INT_ST

Deﬁnition: After conﬁgure empty threshold value and enable interrupts ,it will trigger this

empty interrupt when the data length of the data-send queue is less than the set threshold.

Application: Can be used in forwarding the buffer data into UART automatically with the

cooperation of interrupt handler function.For example,set the empty threshold to 5, then

when the tx ﬁfo length be less than 5 bytes trigger the empty interrupt,in the empty

interrupt handler ,take the data from the buffer to ﬁll the tx ﬁfo full(operating speed is much

higher than tx ﬁfo ﬁfo transmission speed ). Continue the cycle until the buffer data has

totally been sent out, then close the empty interrupt.

Conﬁgure threshold:

Empty interrupt threshold (or threshold) in UART_CONF1 register

#deﬁne UART_TXFIFO_EMPTY_THRHD 0x0000007F //Send queue empty interrupt

threshold conﬁguration bits, seven bits and range 0 ~ 127

#deﬁne UART_TXFIFO_EMPTY_THRHD_S 8 //Register Offset is 8 (start from 8th)

To enable interrupt:

In UART_INT_ENA register

#deﬁne UART_TXFIFO_EMPTY_INT_ENA (BIT(1)) //empty interrupt enable bit, 1: enable;0:

disable

Clear interrupt status:

Fill the sending queue above the threshold,and clear the corresponding interrupt status

bit.If there is no data need to send, close the interrupt enable bits.

Please see details in examples of interrupt handling.

Error detection interrupt

Interrupt status bit:

Parity Error Interrupt UART_PARITY_ERR_INT_ST

Termination line error interrupt(line-break) UART_BRK_DET_INT_ST

Received frame error interrupt

UART_FRM_ERR_INT_ST

Deﬁnition:

Parity error interrupt (parity_err): received byte exists parity error.

Termination line error interrupt(BRK_DET):receive break signal,or receive error initial

conditions (rx line always stays low)

Receive frame error interrupt (frm_err):stop bit is not 1.

Application:

Generally used for error detection.

Espressif

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2017.05

ESP8266 Datasheet(PDF) 93 Page - ESPRESSIF SYSTEMS (SHANGHAI) CO., LTD.