LPC1100系列微控制器UART ?LPC1100系列Cortex-M0微控制器具有一個符合16C550工業標準的異步串行口（UART）。此口同時增加了調制解調器（Modem）接口，DSR、DCD和RI Modem信號是只用于LQFP48和PLCC44封裝的管腳配置。?

?特性 ?

??16字節收發FIFO；?

??寄存器位置符合16C550工業標準； ?

??接收器FIFO觸發點可為1、4、8和14字節；?

??內置波特率發生器； ?

? ?用于精確控制波特率的小數分頻器，并擁有賴以實現軟件流控制的自動波特率檢測能力和機制； ?

? 支持軟件或硬件流控制執行； ?

? 包含標準Modem接口信號（CTS、DCD、DTS、DTR、RI、RTS）；?

? 支持RS-458/EIA-485的9位模式和輸出使能。

【實驗步驟】：

先看一下板子上UART的原理圖

PL-2303HX是一款UART-USB芯片，這里先不管其原理，我們只學習如何將數據從CPU發送到這個TXD RXD處。

一、LPC11C14 UART 寄存器描述

這里只貼出部分

具體寄存器分析，這里不再闡述，先看一下在頭文件中我們這樣定義

[cpp]?view plaincopy

/*-------------?Universal?Asynchronous?Receiver?Transmitter?(UART)?-----------*/??

/**?@addtogroup?LPC11xx_UART?LPC11xx?Universal?Asynchronous?Receiver/Transmitter??

??@{?

*/??

typedef?struct??

{??

??union?{??

??__I??uint32_t??RBR;???????????????????/*!<?Offset:?0x000?Receiver?Buffer??Register?(R/?)?*/??

??__O??uint32_t??THR;???????????????????/*!<?Offset:?0x000?Transmit?Holding?Register?(?/W)?*/??

??__IO?uint32_t??DLL;???????????????????/*!<?Offset:?0x000?Divisor?Latch?LSB?(R/W)?*/??

??};??

??union?{??

??__IO?uint32_t??DLM;???????????????????/*!<?Offset:?0x004?Divisor?Latch?MSB?(R/W)?*/??

??__IO?uint32_t??IER;???????????????????/*!<?Offset:?0x000?Interrupt?Enable?Register?(R/W)?*/??

??};??

??union?{??

??__I??uint32_t??IIR;???????????????????/*!<?Offset:?0x008?Interrupt?ID?Register?(R/?)?*/??

??__O??uint32_t??FCR;???????????????????/*!<?Offset:?0x008?FIFO?Control?Register?(?/W)?*/??

??};??

??__IO?uint32_t??LCR;???????????????????/*!<?Offset:?0x00C?Line?Control?Register?(R/W)?*/??

??__IO?uint32_t??MCR;???????????????????/*!<?Offset:?0x010?Modem?control?Register?(R/W)?*/??

??__I??uint32_t??LSR;???????????????????/*!<?Offset:?0x014?Line?Status?Register?(R/?)?*/??

??__I??uint32_t??MSR;???????????????????/*!<?Offset:?0x018?Modem?status?Register?(R/?)?*/??

??__IO?uint32_t??SCR;???????????????????/*!<?Offset:?0x01C?Scratch?Pad?Register?(R/W)?*/??

??__IO?uint32_t??ACR;???????????????????/*!<?Offset:?0x020?Auto-baud?Control?Register?(R/W)?*/??

???????uint32_t??RESERVED0;??

??__IO?uint32_t??FDR;???????????????????/*!<?Offset:?0x028?Fractional?Divider?Register?(R/W)?*/??

???????uint32_t??RESERVED1;??

??__IO?uint32_t??TER;???????????????????/*!<?Offset:?0x030?Transmit?Enable?Register?(R/W)?*/??

???????uint32_t??RESERVED2[6];??

??__IO?uint32_t??RS485CTRL;?????????????/*!<?Offset:?0x04C?RS-485/EIA-485?Control?Register?(R/W)?*/??

??__IO?uint32_t??ADRMATCH;??????????????/*!<?Offset:?0x050?RS-485/EIA-485?address?match?Register?(R/W)?*/??

??__IO?uint32_t??RS485DLY;??????????????/*!<?Offset:?0x054?RS-485/EIA-485?direction?control?delay?Register?(R/W)?*/??

??__I??uint32_t??FIFOLVL;???????????????/*!<?Offset:?0x058?FIFO?Level?Register?(R)?*/??

}?LPC_UART_TypeDef;??

/*@}*/?/*?end?of?group?LPC11xx_UART?*/??

相關宏定義（部分）

[cpp]?view plaincopy

****************************************************************************/??

#ifndef?__UART_H???

#define?__UART_H??

??

#define?RS485_ENABLED???0??

#define?TX_INTERRUPT????0???????/*?0?if?TX?uses?polling,?1?interrupt?driven.?*/??

#define?MODEM_TEST??????0??

??

#define?IER_RBR?????????(0x01<<0)??

#define?IER_THRE????????(0x01<<1)??

#define?IER_RLS?????????(0x01<<2)??

??

#define?IIR_PEND????????0x01??

#define?IIR_RLS?????????0x03??

#define?IIR_RDA?????????0x02??

#define?IIR_CTI?????????0x06??

#define?IIR_THRE????????0x01??

??

#define?LSR_RDR?????????(0x01<<0)??

#define?LSR_OE??????????(0x01<<1)??

#define?LSR_PE??????????(0x01<<2)??

#define?LSR_FE??????????(0x01<<3)??

#define?LSR_BI??????????(0x01<<4)??

#define?LSR_THRE????????(0x01<<5)??

#define?LSR_TEMT????????(0x01<<6)??

#define?LSR_RXFE????????(0x01<<7)??

??

#define?UART0_RBUF_SIZE?64??

二、UART的初始化

[cpp]?view plaincopy

/*****************************************************************************?

**?Function?name:???????UARTInit?

**?

**?Descriptions:????????Initialize?UART0?port,?setup?pin?select,?

**??????????????????????clock,?parity,?stop?bits,?FIFO,?etc.?

**?

**?parameters:??????????UART?baudrate?

**?Returned?value:??????None?

**??

*****************************************************************************/??

void?UARTInit(uint32_t?baudrate)??

{??

??uint32_t?Fdiv;??

??uint32_t?regVal;??

??

??UARTTxEmpty?=?1;??

??UARTCount?=?0;??

????

??NVIC_DisableIRQ(UART_IRQn);??

??

??LPC_IOCON->PIO1_6?&=?~0x07;????/*??UART?I/O?config?*/??

??LPC_IOCON->PIO1_6?|=?0x01;?????/*?UART?RXD?*/??

??LPC_IOCON->PIO1_7?&=?~0x07;??????

??LPC_IOCON->PIO1_7?|=?0x01;?????/*?UART?TXD?*/??

??

??/*?Enable?UART?clock?*/??

??LPC_SYSCON->SYSAHBCLKCTRL?|=?(1<<12);??

??LPC_SYSCON->UARTCLKDIV?=?0x1;?????/*?divided?by?1?*/??

??

??LPC_UART->LCR?=?0x83;?????????????/*?8?bits,?no?Parity,?1?Stop?bit?*/??

??regVal?=?LPC_SYSCON->UARTCLKDIV;??

??Fdiv?=?((SystemAHBFrequency/regVal)/16)/baudrate?;????/*baud?rate?*/??

??

??LPC_UART->DLM?=?Fdiv?/?256;??????????????????????????????

??LPC_UART->DLL?=?Fdiv?%?256;??

??LPC_UART->LCR?=?0x03;??????/*?DLAB?=?0?*/??

??LPC_UART->FCR?=?0x07;??????/*?Enable?and?reset?TX?and?RX?FIFO.?*/??

??

??/*?Read?to?clear?the?line?status.?*/??

??regVal?=?LPC_UART->LSR;??

??

??/*?Ensure?a?clean?start,?no?data?in?either?TX?or?RX?FIFO.?*/??

??while?((?LPC_UART->LSR?&?(LSR_THRE|LSR_TEMT))?!=?(LSR_THRE|LSR_TEMT)?);??

??while?(?LPC_UART->LSR?&?LSR_RDR?)??

??{??

????regVal?=?LPC_UART->RBR;??/*?Dump?data?from?RX?FIFO?*/??

??}??

???

??/*?Enable?the?UART?Interrupt?*/??

??NVIC_EnableIRQ(UART_IRQn);??

??

#if?TX_INTERRUPT??

??LPC_UART->IER?=?IER_RBR?|?IER_THRE?|?IER_RLS;??/*?Enable?UART?interrupt?*/??

#else??

??LPC_UART->IER?=?IER_RBR?|?IER_RLS;?/*?Enable?UART?interrupt?*/??

#endif??

??return;??

}??

CortexM0 中UART與CPIO口復用，這里看到用到了PIO1_6 與PIO1_7

1、對IO口進行設置

以PIO1_7寄存器為例

可以看到低3位用于配置管腳功能 001為TXD，PIO1_6配置也相同

[cpp]?view plaincopy

LPC_IOCON->PIO1_6?&=?~0x07;????/*??UART?I/O?config?*/??

LPC_IOCON->PIO1_6?|=?0x01;?????/*?UART?RXD?*/??

LPC_IOCON->PIO1_7?&=?~0x07;????

LPC_IOCON->PIO1_7?|=?0x01;?????/*?UART?TXD?*/??

2、時鐘設置

[cpp]?view plaincopy

/*?Enable?UART?clock?*/??

??LPC_SYSCON->SYSAHBCLKCTRL?|=?(1<<12);??

??LPC_SYSCON->UARTCLKDIV?=?0x1;?????/*?divided?by?1?*/??

3、設置波特率、數據位

[cpp]?view plaincopy

LPC_UART->LCR?=?0x83;?????????????/*?8?bits,?no?Parity,?1?Stop?bit?*/??

regVal?=?LPC_SYSCON->UARTCLKDIV;??

Fdiv?=?((SystemAHBFrequency/regVal)/16)/baudrate?;??/*baud?rate?*/??

4、UART相應配置

[cpp]?view plaincopy

LPC_UART->DLM?=?Fdiv?/?256;????????????????????????????

LPC_UART->DLL?=?Fdiv?%?256;??

LPC_UART->LCR?=?0x03;????????/*?DLAB?=?0?*/??

LPC_UART->FCR?=?0x07;????????/*?Enable?and?reset?TX?and?RX?FIFO.?*/??

第4行 FCR為?FIFO控制寄存器。控制UART ?FIFO的使用和模式?

5、使能中斷等操作

[cpp]?view plaincopy

??/*?Read?to?clear?the?line?status.?*/??

??regVal?=?LPC_UART->LSR;??

??

??/*?Ensure?a?clean?start,?no?data?in?either?TX?or?RX?FIFO.?*/??

??while?((?LPC_UART->LSR?&?(LSR_THRE|LSR_TEMT))?!=?(LSR_THRE|LSR_TEMT)?);??

??while?(?LPC_UART->LSR?&?LSR_RDR?)??

??{??

????regVal?=?LPC_UART->RBR;??/*?Dump?data?from?RX?FIFO?*/??

??}??

???

??/*?Enable?the?UART?Interrupt?*/??

??NVIC_EnableIRQ(UART_IRQn);??

??

#if?TX_INTERRUPT??

??LPC_UART->IER?=?IER_RBR?|?IER_THRE?|?IER_RLS;??/*?Enable?UART?interrupt?*/??

#else??

??LPC_UART->IER?=?IER_RBR?|?IER_RLS;?/*?Enable?UART?interrupt?*/??

#endif??

LCR寄存器作用

三、發送數據

[cpp]?view plaincopy

/*****************************************************************************?

**?Function?name:???????UARTSend?

**?

**?Descriptions:????????Send?a?block?of?data?to?the?UART?0?port?based?

**??????????????????????on?the?data?length?

**?

**?parameters:??????????buffer?pointer,?and?data?length?

**?Returned?value:??????None?

**??

*****************************************************************************/??

void?UARTSend(uint8_t?*BufferPtr,?uint32_t?Length)??

{??

????

??while?(?Length?!=?0?)??

??{??

??????/*?THRE?status,?contain?valid?data?*/??

#if?!TX_INTERRUPT??

??????while?(?!(LPC_UART->LSR?&?LSR_THRE)?);??

??????LPC_UART->THR?=?*BufferPtr;??

#else??

??????/*?Below?flag?is?set?inside?the?interrupt?handler?when?THRE?occurs.?*/??

??????while?(?!(UARTTxEmpty?&?0x01)?);??

??????LPC_UART->THR?=?*BufferPtr;??

??????UARTTxEmpty?=?0;??/*?not?empty?in?the?THR?until?it?shifts?out?*/??

#endif??

??????BufferPtr++;??

??????Length--;??

??}??

??return;??

}??

四、接收數據

? ? ? ?這里利用中斷

[cpp]?view plaincopy

/*****************************************************************************?

**?Function?name:???????UART_IRQHandler?

**?

**?Descriptions:????????UART?interrupt?handler?

**?

**?parameters:??????????None?

**?Returned?value:??????None?

**??

*****************************************************************************/??

void?UART_IRQHandler(void)??

{??

??uint8_t?IIRValue,?LSRValue;??

??uint8_t?Dummy?=?Dummy;??

??

??IIRValue?=?LPC_UART->IIR;??

??????

??IIRValue?>>=?1;?????????/*?skip?pending?bit?in?IIR?*/??

??IIRValue?&=?0x07;?????????/*?check?bit?1~3,?interrupt?identification?*/??

??if?(IIRValue?==?IIR_RLS)??????/*?Receive?Line?Status?*/??

??{??

????LSRValue?=?LPC_UART->LSR;??

????/*?Receive?Line?Status?*/??

????if?(LSRValue?&?(LSR_OE?|?LSR_PE?|?LSR_FE?|?LSR_RXFE?|?LSR_BI))??

????{??

??????/*?There?are?errors?or?break?interrupt?*/??

??????/*?Read?LSR?will?clear?the?interrupt?*/??

??????UARTStatus?=?LSRValue;??

??????Dummy?=?LPC_UART->RBR;?/*?Dummy?read?on?RX?to?clear??

????????????????????????????????interrupt,?then?bail?out?*/??

??????return;??

????}??

????if?(LSRValue?&?LSR_RDR)?/*?Receive?Data?Ready?*/??????????????

????{??

??????/*?If?no?error?on?RLS,?normal?ready,?save?into?the?data?buffer.?*/??

??????/*?Note:?read?RBR?will?clear?the?interrupt?*/??

??????UARTBuffer[UARTCount++]?=?LPC_UART->RBR;??

??????if?(UARTCount?>=?UART0_RBUF_SIZE)??

??????{??

????????UARTCount?=?0;??????/*?buffer?overflow?*/??

??????}???

????}??

??}??

??else?if?(IIRValue?==?IIR_RDA)?/*?Receive?Data?Available?*/??

??{??

????/*?Receive?Data?Available?*/??

????UARTBuffer[UARTCount++]?=?LPC_UART->RBR;??

????if?(UARTCount?>=?UART0_RBUF_SIZE)??

????{??

??????UARTCount?=?0;????????/*?buffer?overflow?*/??

????}??

??}??

??else?if?(IIRValue?==?IIR_CTI)?/*?Character?timeout?indicator?*/??

??{??

????/*?Character?Time-out?indicator?*/??

????UARTStatus?|=?0x100;????????/*?Bit?9?as?the?CTI?error?*/??

??}??

??else?if?(IIRValue?==?IIR_THRE)????/*?THRE,?transmit?holding?register?empty?*/??

??{??

????/*?THRE?interrupt?*/??

????LSRValue?=?LPC_UART->LSR;????????/*?Check?status?in?the?LSR?to?see?if?

????????????????????????????????valid?data?in?U0THR?or?not?*/??

????if?(LSRValue?&?LSR_THRE)??

????{??

??????UARTTxEmpty?=?1;??

????}??

????else??

????{??

??????UARTTxEmpty?=?0;??

????}??

??}??

??return;??

}??

下面學習一下UART中斷

對于UART接口來說，有兩種情況可以觸發UART接收中斷：接收字節數達到接收FIFO的觸發點（RDA）、接收超時（CTI）。

(1) 接收字節數達到接收FIFO中的觸發點（RDA）

???? LPC1100系列Cortex-M0微控制器UART接口具有16字節的接收FIFO，接收觸發點可以設置為1、4、8、14字節，當接收到的字節數達到接收觸發點時，便會觸發中斷。

???? 通過UART FIFO控制寄存器U0FCR，將接收觸發點設置為“8字節觸發”。那么當UART接收8個字節時，便會觸發RDA中斷（注：在接收中斷使能的前提下）。

下面看一下IIR

五、其他操作補充

[cpp]?view plaincopy

/*******************************************************************************?

*?Function?Name??:?UART0_PutChar?

*?Description????:?Send?a?char?to?uart0?channel.?

*?Input??????????:?c?

*?Output?????????:?None?

*?Return?????????:?None?

*******************************************************************************/??

void?UART0_PutChar(char?ch)??

{??

??while(!(LPC_UART->LSR?&?LSR_THRE));??

??LPC_UART->THR?=?ch;??

}??

??

/*******************************************************************************?

*?Function?Name??:?uart0_sendstring?

*?Description????:?Send?string?to?uart0?channel.?

*?Input??????????:?pString??--??string?

*?Output?????????:?None?

*?Return?????????:?None?

*******************************************************************************/??

void?UART0_PutString(char?*pString)??

{??

??while(*pString)??

??{??

????UART0_PutChar(*pString++);??

??}??

}??

??

/*******************************************************************************?

*?Function?Name??:?UART0_printf?

*?Description????:?print?format?string.?

*?Input??????????:?fmt?

*?Output?????????:?None?

*?Return?????????:?None?

*******************************************************************************/??

void?UART0_printf(char?*fmt,?...)??

{??

??char??????uart0_pString[101];??

??va_list???uart0_ap;??

??

??va_start(uart0_ap,?fmt);??

??vsnprintf(uart0_pString,?100,?fmt,?uart0_ap);??

??UART0_PutString(uart0_pString);??

??va_end(uart0_ap);??

}??

??

/*******************************************************************************?

*?Function?Name??:?UART0_GetChar?

*?Description????:?print?format?string.?

*?Input??????????:?fmt?

*?Output?????????:?None?

*?Return?????????:?None?

*******************************************************************************/??

uint8_t?UART0_GetChar(uint8_t?*ch)??

{??

??if(UART_op?!=?UARTCount)??

??{??

????*ch?=?UARTBuffer[UART_op];??

????UART_op?++;??

????if(UART_op?>=?UART0_RBUF_SIZE)??

??????UART_op?=?0;??

??

????return?1;??

??}??

??

??return?0;??

} ?

總結

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