(转)CortexM3 (NXP LPC1788)之UART用法

(转)CortexM3 (NXP LPC1788)之UART用法
在工作中经常将平台的串口和PC机连接，通过串口打印信息进行程序调试。LPC1788共有5个串口Uart0~Uart4，跟具开发板的资源，将使用Uart2进行简单的串口输出和输入中断的操作。开发板上使用74HC4052多路开关对UART2的RXD和TXD进行选择，使用SP3243E进行3.0V到5.5V的RS-232电平转换。查看手册配置好相关的跳线帽，保证DB口上的串口输出采用的是Uart2。

       下面介绍Uart相关系统配置和Uart模块的配置。Uart的时钟采用PCLK，我们配置系统的CCLK为120M，PCLK为60M，后面设置串口的波特率就采用PLCK进行计算。要使用串口2的功能需要使能系统时钟控制PCONP，以及配置GPIO管脚为Uart2的RXD和TXD功能。要实现通信，我们需要设置数据的格式，包括传输的波特率，数据长度，停止位，以及校验等，这些数据在线性控制寄存器UnLCR中控制。波特率的产生需要经过分数波特率分频器UnFDR和主分频器DLL，DLM。计数公式如下图。

根据计算，当PLCK=60M，波特率为115200，数据位为8，停止位为1，无校验，则DLL = 22， DLM =0， DivAddVal =1， MulVal = 2 ，线性控制寄存器中的值为0x3。

        要通过串口发送数据时，只需要把要发送的数据写入发送保持寄存器UnTHR，系统就会通过移位寄存器将数据通过串口发送。为了了解系统的发送状态，还需要线性状态寄存器UnLSR，例如程序中使用该该寄存器的第5位判断发怂保持寄存器是否为空，防止数据溢出。

        如果需要进行串口的中断操作，还需要对串口中断进行配置，如串口中断使能寄存器UnIER和串口中断标识寄存器UnIIR。程序中使用到了串口2的接收中断，为此在中断使能设置寄存器ISER中使能UART2中断，在串口中断使能寄存器UnIER中使能串口的接收中断，该中断同时使能了字符接收超时中断。UART2的RXD管脚接收到数据将存放在FIFO中，程序中配置接收FIFO的触发条件为1个字节，即有接收到数据就触发。中断触发后，我们可以根据中断标识寄存器UnIIR判断到底是串口的接收中断，超时中断，发送中断等。进入中断以后，接收中断和超时中断，都可以通过读取接收缓存寄存器UnRBR进行中断复位，使下次中断可以发生。

       下面的程序例子，程序开始打印菜单，PC串口软件发送一个字节数据给开发板，开发板接收到数据后将读取UnRBR前后的中断标识寄存器IIR的值，以及接收到的值发送回给PC。如果是0x5a或者0xa5还可以打开或者关闭LED指示灯。
[cpp] view plain copy print ?
1. #define CCLK 120000000
2. #define PCLK 60000000
4. #define rFIO1DIR (*(volatile unsigned*)(0x20098020))
5. #define rFIO1MASK (*(volatile unsigned*)(0x20098030))
6. #define rFIO1PIN (*(volatile unsigned*)(0x20098034))
7. #define rFIO1SET (*(volatile unsigned*)(0x20098038))
8. #define rFIO1CLR (*(volatile unsigned*)(0x2009803c))
10. #define rISER0 (*(volatile unsigned*)(0xE000E100))
12. #define rCLKSRCSEL (*(volatile unsigned *)(0x400FC10C)) //时钟源选择寄存器
13. #define rPLL0CON (*(volatile unsigned *)(0x400FC080)) //PLL0控制寄存器
14. #define rPLL0CFG (*(volatile unsigned *)(0x400FC084)) //PLL0配置寄存器
15. #define rPLL0STAT (*(volatile unsigned *)(0x400FC088)) //PLL0状态寄存器
16. #define rPLL0FEED (*(volatile unsigned *)(0x400FC08C)) //PLL0馈送寄存器
17. #define rPLL1CON (*(volatile unsigned *)(0x400FC0A0))
18. #define rPLL1CFG (*(volatile unsigned *)(0x400FC0A4))
19. #define rPLL1STAT (*(volatile unsigned *)(0x400FC0A8))
20. #define rPLL1FEED (*(volatile unsigned *)(0x400FC0AC))
21. #define rCCLKSEL (*(volatile unsigned *)(0x400FC104)) //CPU时钟选择寄存器
22. #define rUSBCLKSEL (*(volatile unsigned *)(0x400FC108)) //USB时钟选择寄存器
23. #define rPCLKSEL (*(volatile unsigned *)(0x400FC1A8)) //外设时钟寄存器
24. #define rPCON (*(volatile unsigned *)(0x400FC0C0))
25. #define rPXCONP (*(volatile unsigned *)(0x400FC0C4))
26. #define rSCS (*(volatile unsigned *)(0x400FC1A0)) //系统控制和状态寄存器
27. #define rCLKOUTCFG (*(volatile unsigned *)(0x400FC1C8))
29. #define rIOCON_P0_10 (*(volatile unsigned *)(0x4002C028))
30. #define rIOCON_P0_11 (*(volatile unsigned *)(0x4002C02C))
31. #define rPCONP (*(volatile unsigned *)(0x400FC0C4))
32. #define rU2LCR (*(volatile unsigned *)(0x4009800C))
33. #define rU2FDR (*(volatile unsigned *)(0x40098028))
34. #define rU2DLL (*(volatile unsigned *)(0x40098000))
35. #define rU2DLM (*(volatile unsigned *)(0x40098004))
36. #define rU2TER (*(volatile unsigned *)(0x40098030))
37. #define rU2THR (*(volatile unsigned *)(0x40098000))
38. #define rU2RBR (*(volatile unsigned *)(0x40098000))
39. #define rU2FCR (*(volatile unsigned *)(0x40098008))
40. #define rU2IIR (*(volatile unsigned *)(0x40098008))
41. #define rU2LSR (*(volatile unsigned *)(0x40098014))
42. #define rU2IER (*(volatile unsigned *)(0x40098004))
43. #define rU2ACR (*(volatile unsigned *)(0x40098020))
45. void UART2_IRQHandler()
46. {
47. unsigned int intId;
48. char tmp_char;
50. intId = rU2IIR&0xf;
51. rU2THR = intId;
53. if(intId == 0xc || intId == 0x4) //RDA或者CTI中断
54. {
55. rU2LCR &= ~(0x1<<7); //DLAB=0
56. tmp_char = rU2RBR&0xff;
57. rU2THR = tmp_char;
58. }
59. intId = rU2IIR&0xf;
60. rU2THR = intId;
63. if(tmp_char == 0xa5)
64. rFIO1PIN |= (1<<18);
65. elseif(tmp_char == 0x5a)
66. rFIO1PIN &= ~(1<<18);
67. }
69. void SystemInit()
70. {
71. rSCS &= ~(0x1<<4); //频率12M
72. rSCS |= (0x1<<5); //使能主振荡器
73. while(0 == (rSCS & (0x1<<6)));//等待主振荡器稳定
75. rCLKSRCSEL = 0x1;
77. rPLL0CFG = 0x9; //配置CCLK = 120M
78. rPLL0CON = 0x01;
79. rPLL0FEED = 0xAA;
80. rPLL0FEED =0x55;
81. while(0 == (rPLL0STAT & (0x1<<10)));
83. rCCLKSEL = (0x1 | (0x1<<8));
84. rPCLKSEL = 0x2; //配置PCLK = 60M
85. rCLKOUTCFG = 0x0 | (0xb<<4) | (0x1<<8);
86. }
88. void Init_Uart2()
89. {
90. rPCONP |= 0x1<<24; //使能UART2功率控制
92. rIOCON_P0_10 = (rIOCON_P0_10 & (~0x7)) | 0x1; //P0.10 P0.11做UART2的发送和接收管脚
93. rIOCON_P0_11 = (rIOCON_P0_11 & (~0x7)) | 0x1;
95. rU2LCR |= 0x1<<7; //DLAB=1
96. rU2FDR = 1 | 2<<4; //波特率设置115200
97. rU2DLM = 0;
98. rU2DLL = 22;
99. rU2LCR &= ~(0x1<<7); //DLAB=0
100. rU2LCR |= 0x3; //8位数据位，无校验，1个停止位
102. rU2TER |= 0x1<<7; //使能串口2的发送
104. rU2IER |= 0x1; //使能串口2的接收中断
105. rU2FCR |= 0x1; //复位FIFO,设置接收1个字符触发中断
106. rU2FCR |= 0x1<<1 | 0x1<<2;
107. rISER0 |= 0x1<<7; //使能串口2中断
109. }
111. void Uart2SendC(char c)
112. {
113. rU2THR = c & 0xff;
114. while(!(rU2LSR&(0x1<<5))); //等待rU2THR中的数据发送完成，防止数据溢出
115. }
117. void Uart2SendS(char *s)
118. {
119. while(*s)
120. {
121. Uart2SendC(*s);
122. s++;
123. }
124. }
126. int main(void)
127. {
128. char str[] = {"\n\r1, Display the U2IIR[3:0] + Data + U2IIR[3:0]\n\r2, Send 0x5a ---> Turn on the LED\n\r3, Send 0xa5 --->Turn off the LED\n\r"};
129. rFIO1DIR |= (1<<18); //GPIO1.18 -> OUTPUT
130. Init_Uart2();
131. Uart2SendS(str);
132. while(1);
133. }
```
#define CCLK		120000000
#define PCLK		 60000000

#define rFIO1DIR	(*(volatile unsigned*)(0x20098020))
#define rFIO1MASK 	(*(volatile unsigned*)(0x20098030))
#define rFIO1PIN	(*(volatile unsigned*)(0x20098034))
#define rFIO1SET	(*(volatile unsigned*)(0x20098038))
#define rFIO1CLR	(*(volatile unsigned*)(0x2009803c))

#define rISER0  	(*(volatile unsigned*)(0xE000E100))

#define rCLKSRCSEL  (*(volatile unsigned *)(0x400FC10C))     //时钟源选择寄存器  
#define rPLL0CON    (*(volatile unsigned *)(0x400FC080))     //PLL0控制寄存器  
#define rPLL0CFG    (*(volatile unsigned *)(0x400FC084))     //PLL0配置寄存器  
#define rPLL0STAT   (*(volatile unsigned *)(0x400FC088))     //PLL0状态寄存器  
#define rPLL0FEED   (*(volatile unsigned *)(0x400FC08C))     //PLL0馈送寄存器  
#define rPLL1CON    (*(volatile unsigned *)(0x400FC0A0))       
#define rPLL1CFG    (*(volatile unsigned *)(0x400FC0A4))  
#define rPLL1STAT   (*(volatile unsigned *)(0x400FC0A8))  
#define rPLL1FEED   (*(volatile unsigned *)(0x400FC0AC))  
#define rCCLKSEL    (*(volatile unsigned *)(0x400FC104))     //CPU时钟选择寄存器  
#define rUSBCLKSEL  (*(volatile unsigned *)(0x400FC108))     //USB时钟选择寄存器  
#define rPCLKSEL    (*(volatile unsigned *)(0x400FC1A8))     //外设时钟寄存器  
#define rPCON       (*(volatile unsigned *)(0x400FC0C0))  
#define rPXCONP     (*(volatile unsigned *)(0x400FC0C4))  
#define rSCS        (*(volatile unsigned *)(0x400FC1A0))     //系统控制和状态寄存器  
#define rCLKOUTCFG  (*(volatile unsigned *)(0x400FC1C8))

#define rIOCON_P0_10	(*(volatile unsigned *)(0x4002C028))
#define rIOCON_P0_11	(*(volatile unsigned *)(0x4002C02C))
#define rPCONP		(*(volatile unsigned *)(0x400FC0C4))
#define rU2LCR  	(*(volatile unsigned *)(0x4009800C))
#define rU2FDR		(*(volatile unsigned *)(0x40098028))
#define rU2DLL		(*(volatile unsigned *)(0x40098000))
#define rU2DLM		(*(volatile unsigned *)(0x40098004))
#define rU2TER		(*(volatile unsigned *)(0x40098030))
#define rU2THR		(*(volatile unsigned *)(0x40098000))
#define rU2RBR		(*(volatile unsigned *)(0x40098000))
#define rU2FCR		(*(volatile unsigned *)(0x40098008))
#define rU2IIR		(*(volatile unsigned *)(0x40098008))
#define rU2LSR		(*(volatile unsigned *)(0x40098014))
#define rU2IER		(*(volatile unsigned *)(0x40098004))
#define rU2ACR		(*(volatile unsigned *)(0x40098020))

void UART2_IRQHandler()
{
	unsigned int intId;
	char tmp_char;
	
	intId = rU2IIR&0xf;
	rU2THR = intId;
	
	if(intId == 0xc || intId == 0x4)	//RDA或者CTI中断
	{
		rU2LCR &= ~(0x1<<7);	//DLAB=0
		tmp_char = rU2RBR&0xff;
		rU2THR = tmp_char;
	}
	intId = rU2IIR&0xf;
	rU2THR = intId;

		
	if(tmp_char == 0xa5)
		rFIO1PIN |= (1<<18);
	else if(tmp_char == 0x5a)
		rFIO1PIN &= ~(1<<18);
}
	
void SystemInit()  
{  
    rSCS &= ~(0x1<<4);            //频率12M  
    rSCS |= (0x1<<5);             //使能主振荡器  
    while(0 == (rSCS & (0x1<<6)));//等待主振荡器稳定  
      
    rCLKSRCSEL = 0x1;  
      
    rPLL0CFG = 0x9;                 //配置CCLK = 120M  
    rPLL0CON = 0x01;  
    rPLL0FEED = 0xAA;  
    rPLL0FEED =0x55;  
    while(0 == (rPLL0STAT & (0x1<<10)));   
      
    rCCLKSEL = (0x1 | (0x1<<8));  
    rPCLKSEL = 0x2;                 //配置PCLK = 60M   
    rCLKOUTCFG = 0x0 | (0xb<<4) | (0x1<<8);  
}

void Init_Uart2()
{	
	rPCONP |= 0x1<<24;  	//使能UART2功率控制
	
	rIOCON_P0_10 = (rIOCON_P0_10 & (~0x7)) | 0x1;	//P0.10 P0.11做UART2的发送和接收管脚
	rIOCON_P0_11 = (rIOCON_P0_11 & (~0x7)) | 0x1;

	rU2LCR |= 0x1<<7;		//DLAB=1
	rU2FDR = 1 | 2<<4;  	//波特率设置115200
	rU2DLM = 0;
	rU2DLL = 22;
	rU2LCR &= ~(0x1<<7);	//DLAB=0
	rU2LCR |= 0x3;  		//8位数据位，无校验，1个停止位
	
	rU2TER |= 0x1<<7;		//使能串口2的发送
	
	rU2IER |= 0x1;  		//使能串口2的接收中断
	rU2FCR |= 0x1;  		//复位FIFO,设置接收1个字符触发中断
	rU2FCR |= 0x1<<1 | 0x1<<2;
	rISER0 |= 0x1<<7;		//使能串口2中断
	
}

void Uart2SendC(char c)
{
	rU2THR = c & 0xff;
	while(!(rU2LSR&(0x1<<5)));  	//等待rU2THR中的数据发送完成，防止数据溢出
}

void Uart2SendS(char *s)
{
	while(*s)
	{
		Uart2SendC(*s);
		s++;
	}
}

int main(void)
{
	char str[] = {"\n\r1, Display the U2IIR[3:0] + Data + U2IIR[3:0]\n\r2, Send 0x5a ---> Turn on the LED\n\r3, Send 0xa5 --->Turn off the LED\n\r"};
	rFIO1DIR |= (1<<18); //GPIO1.18 -> OUTPUT
	Init_Uart2();
	Uart2SendS(str);
	while(1);
}
```
运行结果如下图所示

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作者：tdyizhen1314（一位从事软硬件开发十年以上的老兵的故事，希望与大家一起交流，共同进步）邮箱：495567686@qq.com
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原文地址：https://www.cnblogs.com/tdyizhen1314/p/2704590.html