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oyhan
Joined: 03 Jun 2005
Posts: 21
Location: TURKEY
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| 12f675 and ds18b20 |
 Posted: Sun Oct 15, 2006 5:32 am |
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Hi Dear Friends
I need ds18b20 and 12f675 working sample code. I tested a sample code.( below page) But I gets only "TEMP:127 C" on hyper terminal. Would you help us please. Thanks...
| Code: |
#include <12F675.h>
#use delay(clock=4000000)
#fuses NOWDT, XT//,INTRC
#use rs232(baud=9600,xmit=PIN_A2,rcv=PIN_A3, INVERT)
#define Sensor PIN_A0
int Sensor_Reset(void);
int Sensor_Write(int data);
void Sensor_read(void);
int Temp_H[8],Temp_L[8],i;
void main(){
int temp;
setup_adc_ports(NO_ANALOGS);
setup_adc(ADC_OFF);
printf("\r\nWaiting for a Sensor...\r\n");
while (TRUE) {
while(!Sensor_Reset()) ;
Sensor_Write(0xCC);
Sensor_Write(0x44);
delay_ms(200);
if(Sensor_Reset())
{
Sensor_Write(0xCC);
Sensor_Write(0xBE);
Sensor_read();
temp=((Temp_H[0]*64)+(Temp_H[1]*32)+(Temp_H[2]*16)+(Temp_H[3]*8)+(Temp_H[4]*4)+(Temp_H[5]*2)+(Temp_H[6]*1)+(Temp_H[7]?0.51:0.01));
printf("\n\rTemp: %d C\n\r",Temp);
// printf("\n\rTemp: %2.1f C%d%d%d%d%d%d%d%d\n\r",(Temp_L[7]?(-1*Temp):Temp),Temp_L[0],Temp_L[0],Temp_L[2],Temp_L[3],Temp_L[4],Temp_L[5],Temp_L[6],Temp_L[7]);
delay_ms(1000);
}
}
}
int Sensor_Reset(void){
int present;
output_low(Sensor);
delay_us(500);
output_float(Sensor);
delay_us(5);
if(!input(Sensor))
return(FALSE);
delay_us(65);
present=!input(Sensor);
delay_us(240);
if(present)
return(TRUE);
else
return(FALSE);
}
int Sensor_Write(int data){
for(i=1;i<=8;++i){
output_low(Sensor);
delay_us(10);
if(shift_right(&data,1,0)){
output_high(Sensor);
delay_us(10);
}
else{
output_low(Sensor);
delay_us(10);
}
delay_us(50);
output_high(Sensor);
delay_us(50);
}
return(TRUE);
}
void Sensor_read(void){
for(i=0;i<8;i++) {
output_low(Sensor);
delay_us(14);
output_float(Sensor);
delay_us(5);
Temp_H[7-i]=input(Sensor);
delay_us(100);
}
}
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C Turner
Joined: 10 Nov 2003
Posts: 40
Location: Utah
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| Posted: Sun Oct 15, 2006 11:29 am |
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When trying to read from the 18b20, do you have a pullup resistor anywhere?
During conversion, the 18b20 needs a "strong" pullup - something that may be done by setting the pin HIGH, but while reading, the device has only an open drain output: At the very least, the device's weak pullups need to be enabled - but I prefer an external (stronger) pullup - especially if moderate line length is involved.
As for the sensor read/write code, I haven't examined it too closely - except to note that the input code is quite a bit more complex than it need be in that bits are mapped into bytes and then awkwardly converted into decimal using the "temp" variable in the main() function: It is quite easy to simply shift the bit into a byte, then mask, shift, and concatentate as necessary to yield the temperature in C - plenty of examples abound on the web.
CT |
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oyhan
Joined: 03 Jun 2005
Posts: 21
Location: TURKEY
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| Posted: Sun Oct 15, 2006 1:38 pm |
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| I use a pullup resistor in my circuit for I/O port. What can I do for this code Because it doesn't work. Thanks... |
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onurdo
Joined: 16 Oct 2006
Posts: 8
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| Posted: Mon Oct 16, 2006 7:21 pm |
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| I made termometer with ds18b20. You must connect this device parasite power mode |
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