lib_twi.c

IAR EWARM嵌入式系统编程与实践光盘源码

// Basic TWI EEPROM driver

#include "board.h"
#include "lib_twi.h"
#include "main.h"

#define ERROR (AT91C_TWI_NACK)

/*******************************************************************************
 * 说明：AT91F_SetTwiClock函数，初始化
 * 参数：无
 * 返回值：无
*******************************************************************************/
void AT91F_SetTwiClock(void) {
	int sclock;
	/* 这里, CKDIV = 1 and CHDIV=CLDIV  ==> CLDIV = CHDIV = 1/4*((Fmclk/FTWI) -6)*/
	sclock = (10*MCK /AT91C_TWI_CLOCK);
	if (sclock % 10 >= 5)	sclock = (sclock /10) - 5;
	else	sclock = (sclock /10)- 6;
	sclock = (sclock + (4 - sclock %4)) >> 2;	// 除 4
    AT91C_BASE_TWI->TWI_CWGR	= ( 1<<16 ) | (sclock << 8) | sclock  ;
}

/*******************************************************************************
 * 说明：AT91F_TWI_WriteByte函数，向从器件发送一个字节
 * 参数：const AT91PS_TWI pTwi ,int mode, int int_address, char *data2send, int nb
 * 返回值：int
*******************************************************************************/
int AT91F_TWI_WriteByte(const AT91PS_TWI pTwi ,int mode, int int_address, char *data2send, int nb) {
	unsigned int status,counter=0,error=0;
	if ((mode & AT91C_TWI_IADRSZ) != 0)
                pTwi->TWI_IADR = int_address;     // 设置 TWI 内部地址寄存器
        pTwi->TWI_MMR = mode & ~AT91C_TWI_MREAD;  // 设置 TWI 主机模式寄存器
	if(nb <2){
		pTwi->TWI_CR = AT91C_TWI_START | AT91C_TWI_MSEN | AT91C_TWI_STOP;
		pTwi->TWI_THR = *data2send;
	}
	else {
	  for(counter=0;counter<nb;counter++) {     // 设置 TWI 主机模式寄存器
          pTwi->TWI_CR = AT91C_TWI_START | AT91C_TWI_MSEN;
          if (counter == (nb - 1)) pTwi->TWI_CR = AT91C_TWI_STOP;
          status = pTwi->TWI_SR;
          if ((status & ERROR) == ERROR) error++;
          while (!(status & AT91C_TWI_TXRDY)){
               status = pTwi->TWI_SR;
               if ((status & ERROR) == ERROR) error++;
          }
          pTwi->TWI_THR = *(data2send+counter);
	  }
	}
	status = pTwi->TWI_SR;
	if ((status & ERROR) == ERROR) error++;
	while (!(status & AT91C_TWI_TXCOMP)){
    		status = pTwi->TWI_SR;
    		if ((status & ERROR) == ERROR) error++;
    }
	return error;
}

/*******************************************************************************
 * 说明：AT91F_TWI_ReadByte函数，读取从器件一个字节
 * 参数：const AT91PS_TWI pTwi ,int mode, int int_address, char *data, int nb
 * 返回值：int
*******************************************************************************/
int AT91F_TWI_ReadByte(const AT91PS_TWI pTwi ,int mode, int int_address, char *data, int nb) {
	unsigned int status,counter=0,error=0;
	if ((mode & AT91C_TWI_IADRSZ) != 0)
            pTwi->TWI_IADR = int_address;           // 设置 TWI 内部地址寄存器
	pTwi->TWI_MMR = mode | AT91C_TWI_MREAD;     // 设置 TWI 主机模式寄存器
	if (nb == 1){                               // 开始传送
	   pTwi->TWI_CR = AT91C_TWI_START | AT91C_TWI_STOP;
	   status = pTwi->TWI_SR;
    	   if ((status & ERROR) == ERROR) error++;
	   while (!(status & AT91C_TWI_TXCOMP)){
    	      status = pTwi->TWI_SR;
              if ((status & ERROR) == ERROR) error++;
    	   }
	   *(data) = pTwi->TWI_RHR;
	}
 	else{
 	   pTwi->TWI_CR = AT91C_TWI_START | AT91C_TWI_MSEN;
	   status = pTwi->TWI_SR;
	   if ((status & ERROR) == ERROR) error++;
           while (!(status & AT91C_TWI_TXCOMP)){    // 等待传送完毕
   		status = pTwi->TWI_SR;
   		if ((status & ERROR )== ERROR) error++;
    		if(status & AT91C_TWI_RXRDY){
			*(data+counter++) = pTwi->TWI_RHR;
			if (counter == (nb - 1)) pTwi->TWI_CR = AT91C_TWI_STOP;
		}
	   }
	}
	return 0;
}

/*******************************************************************************
 * 说明：AT91F_TWI_Open函数，初始化TWI器件
 * 参数：无
 * 返回值：无
*******************************************************************************/
void AT91F_TWI_Open(void) {
	AT91F_TWI_CfgPIO ();                     // 配置 TWI PIOs
	AT91F_TWI_CfgPMC ();                     // 通过允许TWI时钟来配置PMC
	AT91F_TWI_Configure (AT91C_BASE_TWI);    // 配置TWI主机模式
	AT91F_SetTwiClock();                     // 设置TWI时钟波形发生器寄存器
}