MSP430模拟串口程序
加入技术交流群
比如串口助手发0xaa给413，413接收后把0xaa发送回给PC机，但是串口助手接收到的是0x00或其他数据，
为什么？怎样才能实现一串数据的收发正确？
程序如下（晶振是32768，接413的8和9脚）：
#include <msp430x41x.h>
#define RXD 0x0002 // RXD on P1.1
#define TXD 0x0002 // TXD on P2.1
#define RS4850x0001 //enable 485 on P2.0
// Conditions for 2400 Baud SW UART, ACLK = 32768
#define Bitime_5 0x06 // ~ 0.5 bit length + small adjustment
#define Bitime 0x0E // 427us bit length ~ 2341 baud
unsigned int RXTXData;
unsigned char BitCnt;
void Delay(unsigned int i);
void TX_Byte(void);
void RX_Ready(void);
void main(void)
{
WDTCTL = WDTPW + WDTHOLD; // Stop watchdog timer
FLL_CTL0 |= XCAP14PF; // Configure load caps
CCTL0 |= OUT; // TXD Idle as Mark
TACTL = TASSEL_1 + MC_1; // ACLK, continous mode
P1SEL |= RXD;
P1DIR &= ~RXD;
P2SEL |= TXD;
P2DIR |= TXD;
P2DIR |= RS485;
P2OUT &= ~RS485;
_EINT();
// Mainloop
for(;;)
{
RX_Ready(); // UART ready to RX one Byte
_BIS_SR(LPM3_bits + GIE); // Enter LPM3 Until character RXed
TX_Byte(); // TX Back RXed Byte Received
}
}
void Delay(unsigned int i)
{
unsigned char j;
for(j = 0; j < 5; j ++)
while(i--);
}
// Function Transmits Character from RXTXData Buffer
void TX_Byte(void)
{
P2OUT |= RS485;
Delay(10);
P2OUT &= ~RS485;
BitCnt = 0x0A; // Load Bit counter, 8data + ST/SP
CCR0 = TAR; // Current state of TA counter
CCR0 += Bitime; // Some time till first bit
RXTXData |= 0x0100; // Add mark stop bit to RXTXData
RXTXData = RXTXData << 1; // Add space start bit
CCTL0 = OUTMOD0 + CCIE; // TXD = mark = idle
while(CCTL0 & CCIE); // Wait for TX completion
}
// Function Readies UART to Receive Character into RXTXData Buffer
void RX_Ready(void)
{
BitCnt = 0x08; // Load Bit counter
CCTL0 = SCS + CCIS0 + OUTMOD0 + CM1 + CAP + CCIE; // Sync, Neg Edge, Capture
}
// Timer A0interruptservice routine
interrupt [TIMERA0_VECTOR]
void TimerA0_ISR(void)
{
CCR0 += Bitime; // Add Offset to CCR0
// RX--------------------------------------------------------------------------
if(CCTL0 & CCIS0) // RX on CCI0B?
{
if(CCTL0 & CAP) // Capture mode = start bit edge
{
CCTL0 &= ~CAP; // Capture to compare mode
CCR0 += Bitime_5;
}
else
{
RXTXData = RXTXData >> 1;
if(CCTL0 & SCCI) // Get bit waiting in receive latch
RXTXData |= 0x80;
BitCnt --; // All bits RXed?
if(BitCnt == 0)
//>>>>>>>>>> Decode of Received Byte Here <<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<
{
CCTL0 &= ~CCIE; // All bits RXed, disable interrupt
_BIC_SR_IRQ(LPM3_bits); // Clear LPM3 bits from 0(SR)
}
//>>>>>>>>>> Decode of Received Byte Here <<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<
}
}
// TX--------------------------------------------------------------------------
else
{
if(BitCnt == 0)
CCTL0 &= ~CCIE; // All bits TXed, disable interrupt
else
{
CCTL0 |= OUTMOD2; // TX Space
if(RXTXData & 0x0001)
CCTL0 &= ~OUTMOD2; // TX Mark
RXTXData = RXTXData >> 1;
BitCnt--;
}
}
}
请各位大虾不吝指教！！！
lsdfae18
2006-10-13, 11:49
参考这个程序吧
#define RXD 0x02 // RXD on P1.1
#define TXD 0x01 // TXD on P1.0
// Conditions for 2400 Baud SW UART, ACLK = 32768
#define Bitime_5 0x06 // ~ 0.5 bit length + small adjustment(14/2=7)
#define Bitime 0x0E // 427us bit length ~ 2341 baud (14/32768=427.246us，32768/14=2340.571428)
unsigned int RXTXData;
unsigned char BitCnt; //位计数
void TX_Byte (void);
void RX_Ready (void);
// M.Buccini
// Texas Instruments, Inc
// March 2002
//******************************************************************************
#include
void main (void)
{
WDTCTL = WDTPW + WDTHOLD; // Stop watchdog timer(关闭看门狗模块)
FLL_CTL0 |= XCAP14PF; // Configure load caps(配置振荡器电容)
CCTL0 = OUT; // TXD Idle as Mark(捕获/比较寄存器0：输出高电平)
TACTL = TASSEL0+MC1; // ACLK, continous mode(定时器A：ACLK时钟，连续计 数模式)
P1SEL = TXD + RXD; // PP1.0/1 TA0 for TXD/RXD function(TA0引脚功能)
P1DIR = TXD; // TXD output on P1(输出引脚)
// Mainloop
for (;;)
{
RX_Ready(); // UART ready to RX one Byte(为等待起始位到来作准备)
_BIS_SR(LPM3_bits+GIE); // Enter LPM3 Until character RXed
TX_Byte(); // TX Back RXed Byte Received(回传收到的字节)
}
}
// Function Transmits Character from RXTXData Buffer
void TX_Byte (void)
{
BitCnt = 0xA; // Load Bit counter, 8data + ST/SP(发送10位数据)
CCR0 = TAR; // Current state of TA counter(定时器计数器当前值放比较寄存器中)
CCR0 += Bitime; // Some time till first bit(后推一位的时间)
RXTXData |= 0x100; // Add mark stop bit to RXTXData(填充停止位)
RXTXData = RXTXData << 1; // Add space start bit(填充起始位)
CCTL0 = OUTMOD0+CCIE; // TXD = mark = idle(置位输出模式，允许中断)
while ( CCTL0 & CCIE ); // Wait for TX completion(等待发送完成)
}
// Function Readies UART to Receive Character into RXTXData Buffer
void RX_Ready (void)
{
BitCnt = 0x8; // Load Bit counter(接收8位)
CCTL0 = SCS+CCIS0+OUTMOD0+CM1+CAP+CCIE; // Sync, Neg Edge, Capture
//(CCIxB引脚同步下降沿捕获，置位输出模式，允许中断)
}
// Timer A0 interrupt service routine
interrupt[TIMERA0_VECTOR] void Timer_A (void)
{
CCR0 += Bitime; // Add Offset to CCR0(下一定时时间为1位时间)
// RX(接收字节)
if (CCTL0 & CCIS0) // RX on CCI0B?(如果CCI0B是捕获输入引脚)
{
if( CCTL0 & CAP ) // Capture mode = start bit edge(如果是在捕获模式，则是在等待起始位)
{
CCTL0 &= ~ CAP; // Switch from capture to compare mode(得到起始位后改为比较模式)
CCR0 += Bitime_5; //定时位置改到位的中间位置(加半个位的时间)
}
else
{
RXTXData = RXTXData >> 1; //先收到的是低位
if (CCTL0 & SCCI) // Get bit waiting in receive latch
RXTXData |= 0x80; //SCCI中锁存的是比较相等时的输入引脚上的信号
BitCnt --; // All bits RXed? //位计数减1
if ( BitCnt == 0) //接收完一个字节?
//>>>>>>>>>> Decode of Received Byte Here <<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<
{
CCTL0 &= ~ CCIE; // All bits RXed, disable interrupt(接收完一个字节后禁止中断)
_BIC_SR_IRQ(LPM3_bits); // Clear LPM3 bits from 0(SR)(准备退出 低功耗模式)
}
//>>>>>>>>>> Decode of Received Byte Here <<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<
}
}
// TX(发送字节，在进入发送中断前已经置位OUTMOD0)
else
{
if ( BitCnt == 0) //所有位发送完成
CCTL0 &= ~ CCIE; // All bits TXed, disable interrupt(禁止中断)
else
{
CCTL0 |= OUTMOD2; // TX Space(输出模式OUTMOD2+OUTMOD0：复位)
if (RXTXData & 0x01)
CCTL0 &= ~ OUTMOD2; // TX Mark(输出模式OUTMOD0：置位)
RXTXData = RXTXData >> 1; //低位先发
BitCnt --; //位计数
}
}
}
评论