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串口初始化……
main.c 文件
#include "common.h"
#include "uart.h"
#include "isr.h"
void UART4_Init(U32);
void delay(long count);
void Uart4_SendByte(U8 Char);
void main (void)
{
char str[]="hello cortex-m4 ";
U8 i;
DisableInterrupts;
UART4_Init(57600);
EnableInterrupts;
while(1)
{
for(i=0; str!=''; i++)
Uart4_SendByte(str);
delay(7000000);
}
}
void delay(long count)
{
while(count--)
asm("nop");
}
void UART4_Init(U32 BaudRate)
{
U16 ubd, brfa;
U8 temp;
PORTC_PCR15 = PORT_PCR_MUX(0x3); //引脚使能
PORTC_PCR14 = PORT_PCR_MUX(0x3);
SIM_SCGC1 |= SIM_SCGC1_UART4_MASK; //时钟使能
UART4_C2 &= ~((1<<2) | (1<<3)); //禁止发送接收 控制寄存器C2
UART4_C1 = 0; //控制器C1 全部使用默认配备
ubd = (U16)((50000000)/(BaudRate * 16)); //波特率设置
UART4_BDH = (U8)ubd>>8;
UART4_BDL = (U8)(ubd);
brfa = (((50000000)/(BaudRate * 16)) - (ubd * 32)); //波特率微调 1/32的增量
temp = UART4_C4 & ~(UART_C4_BRFA(0x1F));
UART4_C4 = temp | UART_C4_BRFA(brfa);
UART4_C2 |= ((1<<2) | (1<<3)); //允许发送接收
return;
}
void Uart4_SendByte(U8 Char)
{
while(!(UART_S1_REG(UART4_BASE_PTR) & UART_S1_TDRE_MASK)); //UARTx_S1状态寄存器
UART4_D = Char;
return;
}
isr.h文件
#ifndef EnableInterrupts
#define EnableInterrupts asm(" CPSIE i"); //开总中断
#endif
#ifndef DisableInterrupts
#define DisableInterrupts asm(" CPSID i"); //关总中断
#endif
typedef unsigned short U16;
typedef unsigned long U32;
typedef unsigned char U8;
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串口接收函数
U8 Uart4_Receive(void)
{
U8 Receivechar;
while(!(UART_S1_REG(UART4_BASE_PTR) & UART_S1_RDRF_MASK)); //查询是否接受到数据
Receivechar = UART4_D; //接受到8位的数据
return(Receivechar);
}
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