MSP430 I2C通讯的疑问

hong wu

Other Parts Discussed in Thread: ADS1100, MSP430F149

大家好：
我最近在做亮片MSP430之间的I2C通讯，一个做主机从从机读取数据，使用MSP430自带的P1.6，P1.7口分别做SCL和SDA，使用MSP430自带的I2C接口功能，能够完成通讯，但是如果主机使用IO口模拟I2C通讯，发现作为从机的MSP430对地址没有应答，奇怪的是竟然连主机产生的最后一个SCL脉冲也消失了；但是如果主机向从机写数据，从机对地址就有相应，求高手解答，谢谢！

10 年多前

0 灰小子 10 年多前

Guru 67475 points

既然是用io模拟的I2C通讯，要从代码上找原因。

对照波形，查代码

0 hong wu 10 年多前回复灰小子

Prodigy 41 points

代码之前在ADS1100上使用过，没问题，但是到了MSP430做从机上就少了一个SCL脉冲，

程序如下：
#include <msp430.h>

#define SCL_H  SCL_IN
#define SCL_L  SCLPullDown()
#define SDA_H  SDA_IN
#define SDA_L  SDAPullDown()

#define SCL_OUT  P1DIR |= BIT6
#define SDA_OUT  P1DIR |= BIT7
#define SDA_IN P1DIR &= ~BIT7
#define SCL_IN P1DIR &= ~BIT6

#define SDA_VAL  P1IN & BIT7
#define SCL_VAL  P1IN & BIT6

#define ACK  0X00
#define NACK 0X01
#define ADSADDRESS 0X01

void InitializeClock();
void Start();
void Stop();
unsigned char WriteByte(unsigned char command);
unsigned char ReadByte();
unsigned char CheckACK();
void MACK();
void NMACK();
void Write1();
void Write0();
void SDAPullDown();
void SCLPullDown();

void UartRegCfg();
void UartGpioCfg();
void UartInit();
void UARTPutChar(unsigned char cTX);
void UARTPutstring( char *str);

void main(void) {

      volatile float voltage = 0;
      volatile unsigned char MSB, LSB, parameters;
      volatile unsigned int msb, lsb;
      volatile char VOL[4];
      volatile unsigned int vol;
      UartInit();
      WDTCTL = WDTPW | WDTHOLD;       // Stop watchdog timer
      InitializeClock();
      while(1) {
            Start();
            if(WriteByte(0X91) == ACK) {
                     MSB =ReadByte();
                     MACK();
                     LSB = ReadByte();
                     NMACK();
                     Stop();
            }
            _delay_cycles(800000);
      }
}

void InitializeClock(){
      BCSCTL1 = CALBC1_8MHZ;
      DCOCTL = CALDCO_8MHZ;
}

void Start() {

      SDA_H;
      _delay_cycles(100);
      SCL_H;
      _delay_cycles(100);
      SDA_L;
      _delay_cycles(100);
      SCL_L;
      _delay_cycles(100);

}

void Stop() {

      SDA_L;
      _delay_cycles(100);
      SCL_H;
      _delay_cycles(100);
      SDA_H;
      _delay_cycles(100);
      SCL_L;
      _delay_cycles(100);
}

unsigned char WriteByte(unsigned char command) {

      unsigned char temp, count, ACKFlag;

      for (count = 8; count > 0; count--) {
            temp = command & 0x80;
            if (temp)
                     Write1();
            else
                     Write0();
            command <<= 1;
      }
      ACKFlag = CheckACK();
      return ACKFlag;
}

unsigned char CheckACK() {

      unsigned char flag;

      SDA_IN;

      SCL_L;
      _delay_cycles(100);
      SCL_H;
      _delay_cycles(100);
      flag = SDA_VAL;
      SCL_L;
      _delay_cycles(100);
      if(flag != 0)
            return NACK;
      else
            return ACK;

}

unsigned char ReadByte() {

      unsigned char count, flag;
      unsigned char data = 0;

      SDA_IN;
      SCL_L;

      for(count = 8; count > 0; count--) {

            _delay_cycles(100);
            SCL_H;
            _delay_cycles(100);
            flag = SDA_VAL;
            SCL_L;
            if(flag) {
                     data |= 1;
            }
            if(count == 1) {
                     SDA_OUT;
                     break;
            }
            data <<= 1;
      }
      return data;
}

/*****************************************************************
【函数名称】Mack
【功能】完成IIC的主机应答操作
【参数】无
【返回值  】无
*****************************************************************/
void MACK(void)
{
SDA_L;
__delay_cycles(100);//_NOP(); _NOP();
SCL_L;
_delay_cycles(100);
SCL_H;
__delay_cycles(100);//Delay();
SCL_L;
__delay_cycles(100);//_NOP(); _NOP();
}

/*****************************************************************
【函数名称】MNack
【功能】完成IIC的主机无应答操作
【参数】无
【返回值  】无
*****************************************************************/
void NMACK(void)
{
SDA_H;
__delay_cycles(100);//_NOP(); _NOP();
SCL_H;
__delay_cycles(100);//Delay();
SCL_L;
__delay_cycles(100);//_NOP(); _NOP();
}

void Write1(){

      SDA_H;
      _delay_cycles(100);
      SCL_H;
      _delay_cycles(100);
      SCL_L;

}

void Write0(){

      SDA_L;
      _delay_cycles(100);
      SCL_H;
      _delay_cycles(100);
      SCL_L;
}

void SDAPullDown() {

      SDA_OUT;
      P1OUT &= ~BIT6;
}

void SCLPullDown() {

      SCL_OUT;
      P1OUT &= ~BIT7;
}

0 jing zhang6 10 年多前回复 hong wu

Prodigy 60 points

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MSP430 I2C通讯的疑问