请教DS18B20读取数据为何一直为0？

admin · 发表于 2012-9-2 17:31:31

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使用了C8051F410，片内24.5M时钟。程序是网上找到的，基于AT89C51的。做了点改动，以匹配时序，一直复位成功，但读取数据一直为零。程序如下：
#include <c8051f410.h> // SFR declarations
#include <intrins.h>
#include <stdio.h>

//-----------------------------------------------------------------------------
// 16-bit SFR Definitions for 'F41x
//-----------------------------------------------------------------------------

sfr16 TMR2RL = 0xca; // Timer2 reload value
sfr16 TMR2 = 0xcc; // Timer2 counter
sfr16 ADC0 = 0xbd; // ADC0 result

//-----------------------------------------------------------------------------
// Global CONSTANTS
//-----------------------------------------------------------------------------
#define SYSCLK 24500000 // SYSCLK frequency in Hz
#define BAUDRATE 115200 // Baud rate of UART in bps
#define uchar unsigned char
#define uint unsigned int
#define ulong unsigned long

#define Times1 22 // ÎªÊÊÓ¦DS18B20µÄÊ±Ðò×÷³öµÄµ÷Õû Ñ»·´ÎÊý
#define Times2 22 // ÎªÊÊÓ¦DS18B20µÄÊ±Ðò×÷³öµÄµ÷Õû ÑÓÊ±³¤¶È
//static uchar Times1;
//static uchar Times2;

sbit LED = P2^2; // LED='1' means ON
sbit ConLED1 = P2^3; // Infrared LED Controller ¿ØÖÆ¼ì²âÓÃºìÍâ¶þ¼«¹Ü¿ª¹Ø×´Ì¬
sbit ConLED2 = P2^1; // Infrared LED Controller ¿ØÖÆ¹âÃô¶þ¼«¹Ü×Ô¼ìÓÃµÄ·¢¹â¶þ¼«¹Ü¿ª¹Ø×´Ì¬
sbit REDE = P2^0; // RS485 controller
sbit ds = P0^7; // DS18B20´«¸ÐÆ÷µÄÊý¾Ý½Ó¿Ú

static uchar flag = 0; // DS18B20²Ù×÷±ê×¼±äÁ¿

static ulong accumulator = 0; // accumulator for averaging
static uint measurements = 2048; // measurement counter
static ulong result=0;
static union ADCData { // ¶¨ÓÚADC×ª»»½á¹û12Î»Êý¾Ý
ulong mV; // measured voltage in mV
uchar ch[4]; // °´×Ö½Ú´æ´¢
}myAD0;
static union TempData {
uint Temperature;
uchar ch[2];
}myTemp;
static float vTemp;
//-----------------------------------------------------------------------------
// Function PROTOTYPES
//-----------------------------------------------------------------------------

void SYSCLK_Init (void); // ÏµÍ³Ê±ÖÓ³õÊ¼»¯
void PORT_Init (void); // ÏµÍ³¶Ë¿Ú³õÊ¼»¯
void Timer2_Init(void); // ¶¨Ê±Æ÷³õÊ¼»¯
void ADC0_Init(void); // AD¶Ë¿Ú³õÊ¼»¯
void UART0_Init (void); // ´®¿Ú³õÊ¼»¯
void SendCOM0Byte(uchar ch); // ´®¿Ú·¢Éúµ¥¸ö×Ö½Ú
void TempDelay (uchar us); // ÑÓÊ±×Óº¯Êý
void Delay(uint count); // ÑÓÊ±º¯Êý
void ds_reset(void); // DS18B20¸´Î»
uchar ds_read_byte(void ); // DS18B20¶ÁÒ»×Ö½Ú
void ds_write_byte(uchar dat); // DS18B20Ð´Ò»×Ö½Ú
void tem_change(); // DS18B20½øÐÐÎÂ¶È×ª»»
void get_temperature(); // »ñÈ¡DS18B20½øÐÐÎÂ¶È

//-----------------------------------------------------------------------------
// MAIN Routine
//-----------------------------------------------------------------------------

void main (void)
{
//Times1 = 0;
//Times2 = 0;

PCA0MD &= ~0x40; // WDTE = 0 (clear watchdog timer
// enable)

SYSCLK_Init (); // Initialize system clock to 24.5MHz

PORT_Init (); // Initialize crossbar and GPIO
Timer2_Init(); // Init Timer2 to generate
// overflows to trigger ADC
UART0_Init(); // Initialize UART0 for printf's
ADC0_Init(); // Initialize ADC0

LED = 1; // µãÁÁÖ¸Ê¾ÓÃLED£¬±íÊ¾µ¥Æ¬»úÒÑ¾¿ªÊ¼¹¤×÷
ConLED1 = 1; // ¹Ø±Õ¼ì²âÓÃµÄLED1 ¹âñî¿ª¹Ø
ConLED2 = 0; // ¹Ø±Õ×Ô¼ìÓÃLED2 Èý¼«¹Ü¿ª¹Ø

EA = 0; // enable global interrupts
// ÏÈ¹Ø±ÕÖÐ¶Ï£¬µ÷ÊÔDS18B20
Delay(100);

get_temperature(); // ¶ÁÈ¡ÎÂ¶È
SendCOM0Byte(myTemp.ch[0]); // ·¢ÉúÎÂ¶ÈÊý¾Ý0
SendCOM0Byte(myTemp.ch[1]); // ·¢ËÍÎÂ¶ÈÊý¾Ý1

while (1) { // spin forever

//EA = 0; // Disable interrupt
//TR2 = 0; // Stop timer2

Delay(100);

tem_change(); // Æô¶¯×ª»»
get_temperature(); // ¶ÁÈ¡ÎÂ¶È

//EA = 1; // Enable interrupt
//TR2 = 1; // Start timer2

SendCOM0Byte(myTemp.ch[0]); // ·¢ÉúÎÂ¶ÈÊý¾Ý0
SendCOM0Byte(myTemp.ch[1]); // ·¢ËÍÎÂ¶ÈÊý¾Ý1
//SendCOM0Byte(Times1);
Delay(10000);
//Times1++;
//Times2++;

}
}

//-----------------------------------------------------------------------------
// Initialization Subroutines
//-----------------------------------------------------------------------------

//-----------------------------------------------------------------------------
// SYSCLK_Init
//-----------------------------------------------------------------------------
//
// Return Value : None
// Parameters : None
//
// This routine initializes the system clock to use the internal 24.5MHz
// oscillator as its clock source. Also enables missing clock detector reset.
//
//-----------------------------------------------------------------------------
void SYSCLK_Init (void)
{
OSCICN = 0x87; // configure internal oscillator for
// 24.5MHz ,Ê¹ÄÜÄÚ²¿Õñµ´Æ÷£¬²»·ÖÆµ
RSTSRC = 0x04; // ¸´Î»Ô´¼Ä´æÆ÷£¬enable missing clock detector
}

//-----------------------------------------------------------------------------
// PORT_Init
//-----------------------------------------------------------------------------
//
// Return Value : None
// Parameters : None
//
// Configure the Crossbar and GPIO ports.
// P0.4 - UART TX (push-pull)
// P0.5 - UART RX
// P1.7 - ADC0 analog input
// P2.2 - LED (push-pull)
// P2.1 - Infrared LED controller (weak push-pull)
// P2.0 - REDE (weak push-pull)
//
//-----------------------------------------------------------------------------

void

admin · 发表于 2012-9-2 17:31:36

PORT_Init (void)
{
XBR0 = 0x01; // Enable UART0
XBR1 = 0x40; // Enable crossbar and weak pull-ups
P0MDOUT |= 0x10; // Set TX pin to push-pull ???
P2MDOUT |= 0x08; // enable LED as a push-pull output
P2MDOUT |= 0x04; // ÉèÖÃLED1£¨¼ì²â£©¿ØÖÆ¹Ü½ÅÎªÍÆÍìÉÏÀ
P2MDOUT |= 0x02; // ÉèÖÃLED2£¨×Ô¼ì£©¿ØÖÆ¹Ü½ÅÎªÍÆÍìÉÏÀ
P1MDIN &= 0x7F; // set P1.7 as an analog input, for ADC0
P1SKIP |= 0x80; // skip P1.7 pin

}

//-----------------------------------------------------------------------------
// Timer2_Init
//-----------------------------------------------------------------------------
//
// Return Value : None
// Parameters : None
//
// Configure Timer2 to 16-bit auto-reload and generate an interrupt at 100uS
// intervals. Timer 2 overflow automatically triggers ADC0 conversion.
//
//-----------------------------------------------------------------------------

void Timer2_Init (void)
{
TMR2CN = 0x00; // Stop Timer2; Clear TF2;
// use SYSCLK as timebase, 16-bit
// auto-reload
CKCON = 0x30; // select SYSCLK for timer 2 source
TMR2RL = - (SYSCLK / 10000); // init reload value for 10uS ???
TMR2 = 0xffff; // set to reload immediately
TR2 = 0; // stop Timer2
}

//-----------------------------------------------------------------------------
// ADC0_Init
//-----------------------------------------------------------------------------
//
// Return Value : None
// Parameters : None
//
// Configures ADC0 to make single-ended analog measurements on pin P1.7
//
//-----------------------------------------------------------------------------
void ADC0_Init (void)
{
ADC0CN = 0x03; // ADC0 disabled, normal tracking,
// conversion triggered on TMR2 overflow
// right-justify result

REF0CN = 0x13; // Enable on-chip VREF = 2.2v and buffer
/*
P1MDIN &= 0xFB; // set P1.2 as an analog input, VREF input
P1SKIP |= 0x04; // skip P1.2 pin
REF0CN = 0x02; // Íâ²¿VREF×÷Îª²Î¿¼µçÑ¹
*/
ADC0MX = 0x0f; // Set P1.7 as positive input

// ADC0MX = 0x18; // ÎÂ¶È´«¸ÐÆ÷ÊäÈë

ADC0CF = ((SYSCLK/3000000)-1)<<3; // set SAR clock to 3MHz

ADC0CF |= 0x00; // only 1 times ADC

EIE1 |= 0x08; // enable ADC0 conversion complete interrupt.

AD0EN = 1; // enable ADC0
}

//-----------------------------------------------------------------------------
// UART0_Init
//-----------------------------------------------------------------------------
//
// Return Value : None
// Parameters : None
//
// Configure the UART0 using Timer1, for <BAUDRATE> and 8-N-1.
//
//-----------------------------------------------------------------------------
void UART0_Init (void)
{
SCON0 = 0x10; // SCON0: 8-bit variable bit rate
// level of STOP bit is ignored
// RX enabled
// ninth bits are zeros
// clear RI0 and TI0 bits£¬¹Ø±Õ½ÓÊÕ¼°·¢ËÍÖÐ¶Ï
if (SYSCLK/BAUDRATE/2/256 < 1) {
TH1 = -(SYSCLK/BAUDRATE/2);
CKCON |= 0x08; // T1M = 1; SCA1:0 = xx
} else if (SYSCLK/BAUDRATE/2/256 < 4) {
TH1 = -(SYSCLK/BAUDRATE/2/4);
CKCON &= ~0x0B; // T1M = 0; SCA1:0 = 01
CKCON |= 0x01;
} else if (SYSCLK/BAUDRATE/2/256 < 12) {
TH1 = -(SYSCLK/BAUDRATE/2/12);
CKCON &= ~0x0B; // T1M = 0; SCA1:0 = 00
} else if (SYSCLK/BAUDRATE/2/256 < 48) {
TH1 = -(SYSCLK/BAUDRATE/2/48);
CKCON &= ~0x0B; // T1M = 0; SCA1:0 = 10
CKCON |= 0x02;
} else {
while (1); // Error. Unsupported baud rate
}

TL1 = TH1; // init Timer1
TMOD &= ~0xf0; // TMOD: timer 1 in 8-bit autoreload
TMOD |= 0x20;
TR1 = 1; // START Timer1
TI0 = 1; // Indicate TX0 ready
}

//-----------------------------------------------------------------------------
// Interrupt Service Routines
//-----------------------------------------------------------------------------
//
//-----------------------------------------------------------------------------
// ADC0_ISR
//-----------------------------------------------------------------------------
//
// This ISR averages 2048 samples then prints the result to the terminal. The
// ISR is called after each ADC conversion which is triggered by Timer2.
//
//-----------------------------------------------------------------------------
void ADC0_ISR (void) interrupt 10
{

AD0INT = 0; // clear ADC0 conv. complete flag

// if(ADC0==0x0fff) return; // È¥³ýÒì³£µã

accumulator += ADC0;

measurements--;

if(measurements == 0)
{
measurements = 2048;
result = accumulator / 2048;
accumulator = 0;

// The 12-bit ADC value is averaged across 2048 measurements.
// The measured voltage applied to P1.7 is then:
//
// Vref (mV)
// measurement (mV) = --------------- * result (bits)
// (2^12)-1 (bits)

myAD0.mV = result * 2200 / 4095; // ¼ÆËãÆ½¾ùÖµ »ù×¼µçÑ¹2.2V
// myAD0.mV = ADC0 * 2200 / 4095;
// myAD0.mV = result;

// vTemp = (100*(myAD0.mV-900))/295.0; // ×ª»»³É»ªÊÏÎÂ¶È
// vTemp = (5*vTemp-160)/9.0; // ×ª»»³ÉÉãÊÏÎÂ¶È
// myAD0.mV = (ulong)vTemp;

//SendCOM0Byte(myAD0.ch[0]); // ·¢ËÍµ½´®¿Ú0
//SendCOM0Byte(myAD0.ch[1]);
SendCOM0Byte(myTemp.ch[0]); // ·¢ÉúÎÂ¶ÈÊý¾Ý0
SendCOM0Byte(myTemp.ch[1]); // ·¢ËÍÎÂ¶ÈÊý¾Ý1

SendCOM0Byte(myAD0.ch[2]);
SendCOM0Byte(myAD0.ch[3]);

// printf("P1.1 voltage: %ld mV\n",mV);
}
}

//-----------------------------------------------------------------------------
// SendCOM0Byte : Send COM0 a Byte Servive Routines
//-----------------------------------------------------------------------------
//
// Return value : None
// Parameter : byte to be send -- ch
//-----------------------------------------------------------------------------
void SendCOM0Byte(uchar ch)
{
// ES0 = 0; // ¹Ø±Õ´®¿ÚÖÐ¶Ï
TI0 = 0; // ÇåÁã´®¿Ú·¢ËÍÍê³É±êÖ¾
SBUF0 = ch; // ·¢ËÍ´®¿ÚÊý¾Ý
while(TI0==0); // µÈ´ý´®¿Ú·¢ËÍÍê³É
TI0 = 0; // ÇåÁã´®¿Ú·¢ËÍÍê³É±êÖ¾
// ES0 = 0; // ÔÊÐí´®¿ÚÖÐ¶Ï
}

//-----------------------------------------------------------------------------
// ÑÓÊ±×Ó³ÌÐò
//-----------------------------------------------------------------------------
//
// ·µ»ØÖµ£ºÎÞ
// ²Î Êý£ºus ÎÞ·ûºÅ×Ö½Ú
//-----------------------------------------------------------------------------
void TempDelay (uchar us)
{
while(us--);
}

//-----------------------------------------------------------------------------
// ÑÓÊ±³ÌÐò
//-----------------------------------------------------------------------------
//
//

admin · 发表于 2012-9-2 17:31:40

·µ»ØÖµ£ºÎÞ
// ²Î Êý£ºcount ÎÞ·ûºÅÕûÊý
//-----------------------------------------------------------------------------
void Delay(uint count) //ÑÓÊ±×Óº¯Êý
{
static uint i;
while(count)
{
i=200;
while(i>0) i--;
count--;
}
}

//-----------------------------------------------------------------------------
// DS18B20¸´Î»³ÌÐò
//-----------------------------------------------------------------------------
//
// ·µ»ØÖµ£ºÎÞ
// ²Î Êý£ºÎÞ
//-----------------------------------------------------------------------------
void ds_reset(void)
{
uchar j;

ds=0; //µ±×ÜÏßÍ£ÁôÔÚµÍµçÆ½³¬¹ý480us£¬×ÜÏßÉÏËùÒÔÆ÷¼þ¶¼½«±»¸´Î»£¬ÕâÀïÑÓÊ±Ô¼530us×Ü
//ÏßÍ£ÁôÔÚµÍµçÆ½³¬¹ý480¦Ìs£¬×ÜÏßÉÏµÄËùÓÐÆ÷¼þ¶¼½«±»¸´Î»¡£
for(j=0;j<Times1;j++) TempDelay(60);

ds=1; // ²úÉú¸´Î»Âö³åºó£¬Î¢´¦ÀíÆ÷ÊÍ·Å×ÜÏß,ÈÃ×ÜÏß´¦ÓÚ¿ÕÏÐ×´Ì¬£¬ÔÒò²é//18b20ÖÐÎÄ×ÊÁÏ
// ÊÍ·Å×ÜÏßºó£¬ÒÔ±ã´Ó»ú18b20Í¨¹ýÀµÍ×ÜÏßÀ´Ö¸Ê¾ÆäÊÇ·ñÔÚÏß,
// ´æÔÚ¼ì²â¸ßµçÆ½Ê±¼ä£º15~60us£¬ ËùÒÔÑÓÊ±44us£¬½øÐÐ 1-wire presence //detect£¨µ¥Ïß´æÔÚ¼ì²â£©
for(j=0;j<Times1;j++) TempDelay(4); // Ò»¶¨Òª³¬¹ý60uS£¬²ÅÄÜ¼ì²â¸´Î»µçÆ½ÐÅºÅ

if(ds==0) flag=1; //detect 18b20 success
else flag=0; //detect 18b20 fail

for(j=0;j<200;j++) TempDelay(20); //´æÔÚ¼ì²âµÍµçÆ½Ê±¼ä£º60~240us£¬ËùÒÔÑÓÊ±Ô¼140us

SendCOM0Byte(flag);

}

//-----------------------------------------------------------------------------
// DS18B20¶ÁÒ»¸ö×Ö½Ú³ÌÐò
//-----------------------------------------------------------------------------
//
// ·µ»ØÖµ£ºuchar ¶ÁÈ¡×Ö½Ú
// ²Î Êý£ºÎÞ
//-----------------------------------------------------------------------------
uchar ds_read_byte(void ) //¶ÁÒ»×Ö½Ú
{
uchar dat,i,j;

dat = 0; //Ò»¶¨±ðÍüÁË¸ø³õÖµ
for(i=0;i<8;i++)
{
ds = 0;
for(j=0;j<Times1;j++) { _nop_(); _nop_(); } //¶ÁÊ±Ï¶ÆðÊ¼ÓÚÎ¢´¦ÀíÆ÷½«×ÜÏßÀµÍÖÁÉÙ1us
dat>>=1;
if(ds) dat|=0x80;
for(j=0;j<Times1;j++) TempDelay(5);
ds = 1;
for(j=0;j<Times1;j++) { _nop_(); _nop_(); }
}
return(dat); //·µ»ØÒ»¸ö×Ö½ÚµÄÊý¾Ý
}

//-----------------------------------------------------------------------------
// DS18B20Ð´Ò»¸ö×Ö½Ú
//-----------------------------------------------------------------------------
//
// ·µ»ØÖµ£ºÎÞ
// ²Î Êý£ºuchar data£¬Ð´ÈëµÄ×Ö½ÚÊý¾Ý
//-----------------------------------------------------------------------------
void ds_write_byte(uchar dat) //Ð´Ò»¸ö×Ö½Ú
{
uchar i,j;

for(i=1;i<=8;i++)
{
ds = 0;
for(j=0;j<Times1;j++) TempDelay(2);
ds = dat&0x01;
for(j=0;j<Times1;j++) TempDelay(5);
ds = 1;
dat>>=1;
}
// for(j=0;j<Times1;j++) TempDelay(5);
}

//-----------------------------------------------------------------------------
// DS18B20½øÐÐÎÂ¶È×ª»»
//-----------------------------------------------------------------------------
//
// ·µ»ØÖµ£ºÎÞ
// ²Î Êý£ºÎÞ
//-----------------------------------------------------------------------------
void tem_change()
{
ds_reset();
Delay(10); //Ô¼2ms
ds_write_byte(0xcc);
ds_write_byte(0x44);
return;
}

//-----------------------------------------------------------------------------
// DS18B20»ñÈ¡ÎÂ¶È
//-----------------------------------------------------------------------------
//
// ·µ»ØÖµ£ºÎÞ£¬·µ»ØµÄÎÂ¶È´æ·ÅÔÚtempÖÐ¡£
// ²Î Êý£ºÎÞ
//-----------------------------------------------------------------------------
void get_temperature()
{
float wendu;

ds_reset();
Delay(10); //Ô¼2ms
ds_write_byte(0xcc);
ds_write_byte(0xbe);
myTemp.ch[1]=ds_read_byte();
myTemp.ch[0]=ds_read_byte();

wendu=myTemp.Temperature*0.0625; //µÃµ½ÕæÊµÊ®½øÖÆÎÂ¶ÈÖµ£¬ÒòÎªDS18B20
//¿ÉÒÔ¾«È·µ½0.0625¶È£¬ËùÒÔ¶Á»ØÊý¾ÝµÄ×îµÍÎ»´ú±íµÄÊÇ //0.0625¶È

myTemp.Temperature=wendu*10+0.5; //·Å´óÊ®±¶£¬ÕâÑù×öµÄÄ¿µÄ½«Ð¡ÊýµãºóµÚÒ»Î»
//Ò²×ª»»Îª¿ÉÏÔÊ¾Êý×Ö£¬Í¬Ê±½øÐÐÒ»¸öËÄÉáÎåÈë²Ù×÷
}

admin · 发表于 2012-9-2 17:31:43

//-----------------------------------------------------------------------------
// End Of File
//-----------------------------------------------------------------------------

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