AD7705应用注意要点

来源：本站时间：2023-06-13 04:56:12

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AD7705应用注意要点：

（1） DRDY逻辑不要搞反，高电平时等待转换状态，低电平为可以读取转换数据

（2）系统校准时输入信号要大于所选量程的4/5，否则校准不到32767。

（3）校准时要等待一定的时间，读取数据也一样，不能超过转换速率。

（4）一般的应用只要内部校准，这个很简单，只要初始化就可以。如果测量范围不是芯片的范围，可以通过系统校准来实现，满量程校准电压要大于量程的4/5

#include <util/delay.h>

#include <avr/eeprom.h>

#include "ad7705.h"

#include "main.h"

#include "crc16.h"

#include "Usart.h"

//针对四个量程的设置寄存器的设置内容

//（1）对于单极性V级别输入0-5V、0-20mA、0-10V这三个量程，输入范围为0-2V，无极性，增益为1，缓冲模式--0-2V

//（2）对于双极性V级别输入+-2.5V、+-5V这两个量程，输入范围为+-1V，双极性，增益为2，缓冲模式--+-2V

//（3）对于双精度mV级别输入+-500mV，增益为4，双极性，缓冲模式--+-2V

//（4）对双精度mV级别+-50mV，增益为32，双极性，缓冲模式--+-1.6V

//------MD1(0) MD0(0) G2(0) G1(0) G0(0) B/U(0) BUF(0) FSYNC(0)--------------------------//

const unsigned char text_of_setup[4]={0X04,0X08,0X10,0X28}; //非缓冲模式,数字滤波同步

//const unsigned char text_of_setup[4]={0X06,0X0A,0X12,0X2A}; //缓冲模式，数字滤波同步

extern volatile unsigned charcommand[7]; //校准命令全局数组

extern volatile unsigned charscale; //记录系统量程

extern volatile unsigned charNO_CALI_TYPE; //未校准类型

extern volatile unsigned longint ZS,GS; //当前量程的校准系数

extern volatile unsigned chartime_count; //超时标志

//----------------------------------------------------------------------------

//函数：reset_AD7705

//功能：AD7705串行接口失步后将其复位。复位后要延时500us再访问

//参数：无

//返回：无

//变量：无

//备注：无

//----------------------------------------------------------------------------

void reset_AD7705(void)

{

unsigned char i;

AD_DIN1;

for( i=0; i<36; i++ )

{

AD_CLK0;

asm("nop");

AD_CLK1;

asm("nop");

}

_delay_ms(1);

}

//------------------------------------------------------------------------------------------

//函数：read_AD7705_byte

//功能：从AD7705读一个字节的数据

//参数：无

//返回：读到的一字节数据

//变量：无

//备注：无

//------------------------------------------------------------------------------------------

unsigned char read_AD7705_byte(void)

{

unsigned char data = 0;

unsigned char i = 0;

for( i=0; i<8; i++ )

{

data <<= 1;

AD_CLK0;

asm("nop");

if(AD_DOUT)

{

data++;

}

AD_CLK1;

asm("nop");

}

return data;

}

//------------------------------------------------------------------------------------------

//函数：read_AD7705_word

//功能：从AD7705读一个字的数据，共16bit

//参数：无

//返回：读到的一字节数据

//变量：无

//备注：无

//------------------------------------------------------------------------------------------

unsigned int read_AD7705_word(void)

{

unsigned int data = 0;

unsigned char i = 0;

for( i=0; i<16; i++ )

{

data <<= 1;

AD_CLK0;

asm("nop");

if(AD_DOUT)

{

data++;

}

AD_CLK1;

asm("nop");

}

return data;

}

//------------------------------------------------------------------------------------------

//函数：read_AD7705_dword

//功能：从AD7705读一个24的数据

//参数：无

//返回：读到的一字节数据

//变量：无

//备注：AD7705是一个24位AD，选定刷新频率在16.7HZ下，有效位是19位，暂时读出全部24位数据

//------------------------------------------------------------------------------------------

unsigned long int read_AD7705_dword(void)

{

unsigned long data = 0;

unsigned char i = 0;

for( i=0; i<24; i++ )

{

data <<= 1;

AD_CLK0;

asm("nop");

if(AD_DOUT)

{

data++;

}

AD_CLK1;

asm("nop");

}

return data;

}

//------------------------------------------------------------------------------------------

//函数：write_AD7705_byte

//功能：往AD7705写8位数据

//参数：IN - uint8_tdata,要写入AD7705的数据

//返回：无

//变量：无

//备注：无

//------------------------------------------------------------------------------------------

void write_AD7705_byte(unsigned char data)

{

for(unsigned char i=0; i<8; i++)

{

AD_CLK0;

if(data&0x80)

AD_DIN1;

else

AD_DIN0;

asm("nop");

AD_CLK1;

asm("nop");

data <<= 1;

}

AD_DIN1;

}

//------------------------------------------------------------------------------------------

//函数：write_AD7705_dword

//功能：往AD7705写24位数据,因为AD7705是24位的器件

//参数：IN - int32_tdata,要写入AD7705的数据

//返回：无

//变量：无

//备注：无

//------------------------------------------------------------------------------------------

void write_AD7705_dword(unsigned long int data)

{

for(unsigned char i = 0; i<24; i++)

{

AD_CLK0;

if(data&0x800000)

AD_DIN1;

else

AD_DIN0;

asm("nop");

AD_CLK1;

asm("nop");

data <<= 1;

}

AD_DIN1;

}

//--------------------------------------------------------------------------

//-------------------------读取AD7705转换数据函数--------------------------

//入口参数：指向main()主函数定义的ad_data变量的常量指针

//--------------------------------------------------------------------------

void ReadData7705(unsigned int *const pdata)

{

unsigned int data=0, fiter[5]={0};

unsigned long int temp=0;

unsigned char i=0, sort_flag=1;

AD_CS0;

_delay_us(5);

start_AD7705();

for( i=0; i<5; i++ )

{

start_timer0();

_delay_ms(2);

while( AD_DRDY )

{

if( time_count >= time_read_data )

{

stop_timer0();

AD_CS1;

return;

}

stop_timer0();

write_AD7705_byte( RD_DATA_REG );

fiter = read_AD7705_word();

}

AD_CS1;

sort_flag = 1;

while( sort_flag )

{

sort_flag = 0;

for( i=0; i<4; i++ )

{

if( fiter > fiter[i+1] )

{

data = fiter;

fiter = fiter[i+1];

fiter[i+1] = data;

sort_flag = 1;

}

temp = ( (unsigned long int)fiter[1] + (unsigned long int)fiter[2]

+ (unsigned long int)fiter[3] )/3;

data = (unsigned int)temp;

if( (data<0xfff0) && (data&0x000f)>0x0008 )

{

data >>= 4;

data++;

}

else

{

data >>= 4;

}

if( 1 != scale )

{

data -= 0x0800;

}

*pdata = data & 0x0fff;

}

//---------------------------------------------------------------------------------------

//校准命令格式

//STX Data Long Command Code Parameter CheckSum ETX

//0x55 数据长度（2）量程指示 00H/01H CRC16(2) 0x0D

void AD7705_calibration(void)

{

unsigned char readtimes =0;

unsigned char cali_scale =0;

unsigned long int temp =0;

unsigned char coefficient[8] ={0}; //test[8]={0};

//16位校验和的临时变量

unsigned int crcvalue =0;

AD_CS1;

cali_scale = command[2]; //获取上位机发送的要校准的量程类型

eeprom_busy_wait();

eeprom_read_block( &coefficient[0], (void*)(ADDR_EEPROM_1+(cali_scale-1)*10), 8 );

crcvalue = checksum( &coefficient[0], 6 );

if( (coefficient[7]*256+coefficient[6]) != crcvalue )

{

readtimes++;

}

if( 1 == readtimes )

{

eeprom_busy_wait();

eeprom_read_block( &coefficient[0], (void*)(ADDR_EEPROM_2+(cali_scale-1)*10), 8 );

crcvalue = checksum( &coefficient[0], 6 ); //

if( (coefficient[7]*256+coefficient[6]) != crcvalue )

{

readtimes++;

}

if( 2 == readtimes )

{

eeprom_busy_wait();

eeprom_read_block( &coefficient[0], (void*)(ADDR_EEPROM_3+(cali_scale-1)*10), 8 );

}

ADDR409_MASK;

AD_CS0;

_delay_us(5);

reset_AD7705();

write_AD7705_byte( WR_CLOCK_REG );

write_AD7705_byte( CLOCK_REG_SET );

if( ZERO_CALIBRATION == command[3] ) //校准命令为零校准

{

write_AD7705_byte( WR_SETUP_REG );

write_AD7705_byte( text_of_setup[cali_scale-1] | SYS_ZERO_CALI);

//等待校准完成

start_timer0();

while( time_count < time_sys_cali );

stop_timer0();

while( AD_DRDY );

//读OFFSET寄存器

write_AD7705_byte( RD_OFFSET_REG );

temp = read_AD7705_dword();

if( cali_scale == scale)

{

ZS = temp; NO_CALI_TYPE = NO_FULL_CALIBRATION;

}

coefficient[0] = (unsigned char)( temp%256 );

coefficient[1] = (unsigned char)( (temp/256)%256 );

coefficient[2] = (unsigned char)( (temp/65536)%256 );

}

else if( FULL_CALIBRATION == command[3] )

{

temp = (unsigned long int)(coefficient[0]) + (unsigned long int)(coefficient[1])*256

+ (unsigned long int)(coefficient[2])*65536;

write_AD7705_byte( WR_OFFSET_REG );

write_AD7705_dword( temp );

write_AD7705_byte( WR_SETUP_REG );

write_AD7705_byte( text_of_setup[cali_scale-1] | SYS_FULL_CALI );

//等待校准完成

start_timer0();

while( time_count < time_sys_cali );

stop_timer0();

while( AD_DRDY );//

//读FULL寄存器

write_AD7705_byte( RD_FULL_REG );

temp = read_AD7705_dword();

if( cali_scale == scale )

{

GS = temp;

NO_CALI_TYPE = ALREADY_CALIBRATION;

}

coefficient[3] = (unsigned char)( temp%256 );

coefficient[4] = (unsigned char)( (temp/256)%256 );

coefficient[5] = (unsigned char)( (temp/65536)%256 );

}

else

{

AD_CS1;

_delay_us(5);

return;

}

AD_CS1;

_delay_us(5);

crcvalue = checksum(&coefficient[0],6);

coefficient[6] = (unsigned char)(crcvalue%256);//

coefficient[7] = (unsigned char)(crcvalue/256);

eeprom_busy_wait();

eeprom_write_block( &coefficient[0], (void*)(ADDR_EEPROM_1+(cali_scale-1)*10), 8 );

eeprom_busy_wait();

eeprom_write_block( &coefficient[0], (void*)(ADDR_EEPROM_2+(cali_scale-1)*10), 8 );

eeprom_busy_wait();

eeprom_write_block( &coefficient[0], (void*)(ADDR_EEPROM_3+(cali_scale-1)*10), 8 );

Txout( &coefficient[0] );//输出校准数据给上位机

return;

}

void start_AD7705(void)

{

reset_AD7705();

//写OFFSET寄存器

write_AD7705_byte( WR_OFFSET_REG );

write_AD7705_dword( ZS );

//写满量程校准寄存器

write_AD7705_byte( WR_FULL_REG );

write_AD7705_dword( GS );

//CLOCK寄存器设置，无分频，50HZ输出更新速率

write_AD7705_byte( WR_CLOCK_REG );

write_AD7705_byte( CLOCK_REG_SET );

//写设置寄存器

write_AD7705_byte( WR_SETUP_REG );

write_AD7705_byte( text_of_setup[scale-1] );

start_timer0();

while( time_count < time_read_data );

stop_timer0();

}

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