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Joined: 24 Mar 2015
Posts: 14
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| PROBLEM DS18B20 + PIC 18F4550 |
 Posted: Sun Apr 05, 2015 2:01 pm |
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I am doing data acquisition unit and I use this sensor. My problem is the following, when I simulate in Proteus and running, but when I load the program through the PICKIT, the sensor reads a temperature of -0.5 ° C. I do not know this happens because my sensor. If someone could advise me. I read the protocol of this sensor, but I can not find solution. Would need to fix this, because I'm doing a project.
Thanks
I use:
-18F4550
-DS18B20
-20MHz
-CHANNEL 0
And my code:
MAIN CODE:
| Code: |
#include <18F4550.h>
//#device *=18
//#device adc=10
#FUSES NOWDT, HS, PUT, NOPROTECT, NODEBUG, BROWNOUT, NOLVP, NOCPD, NOWRT
#use delay(clock=20000000)
#include "C:\Users\Albert\Desktop\ds18b20(2)\1wire.c"
#include "C:\Users\Albert\Desktop\ds18b20(2)\flex_lcd420.c"
#include "C:\Users\Albert\Desktop\ds18b20(2)\ds1820.c"
void main()
{
float temperature;
setup_adc_ports(NO_ANALOGS);
setup_adc(ADC_OFF);
setup_psp(PSP_DISABLED);
setup_spi(FALSE);
setup_timer_0(RTCC_INTERNAL|RTCC_DIV_1);
setup_timer_1(T1_DISABLED);
setup_timer_2(T2_DISABLED,0,1);
setup_comparator(NC_NC_NC_NC);
setup_vref(VREF_LOW|-2);
lcd_init();
lcd_putc("\f");
while (TRUE)
{
temperature = ds1820_read();
lcd_gotoxy(1,1);
printf(lcd_putc,"TEMP: %3.1f ", temperature);
lcd_putc(223);
lcd_putc("C ");
lcd_gotoxy(1,2);
if(temperature >= 29.0)
printf(lcd_putc,"Hot! ");
else if( temperature >= 20 && temperature < 29.0)
printf(lcd_putc,"Comfort!");
else
printf(lcd_putc,"Cold! ");
}
} |
LCD CODE:
| Code: |
// Flex_LCD420.c
// These pins are for my Microchip PicDem2-Plus board, which I used to test this driver.
// An external 20x4 LCD is connected to these pins.
// Change these pins to match your own board's connections.
#define LCD_DB7 PIN_C7 // pin 14 LCD // Asignación de pines LCD-PIC en el diseño.
#define LCD_DB6 PIN_C6 // pin 13 LCD
#define LCD_DB5 PIN_C2 // pin 12 LCD
#define LCD_DB4 PIN_C1 // pin 11 LCD
#define LCD_E PIN_E2 // pin 06 LCD
//#define LCD_RW PIN_B0 // pin 05 LCD It is earthed at the display.
#define LCD_RS PIN_E1
// If you want only a 6-pin interface to your LCD, then connect the R/W pin on the LCD to ground,
// and comment out the following line. Doing so will save one PIC pin,
// but at the cost of losing the ability to read from the LCD.
// It also makes the write time a little longer because a static delay must be used,
// instead of polling the LCD's busy bit. Normally a 6-pin interface is only
// used if you are running out of PIC pins, and you need to use as few as possible for the LCD.
//#define USE_RW_PIN 1
// These are the line addresses for most 4x20 LCDs.
#define LCD_LINE_1_ADDRESS 0x00
#define LCD_LINE_2_ADDRESS 0x40
#define LCD_LINE_3_ADDRESS 0x14
#define LCD_LINE_4_ADDRESS 0x54
// These are the line addresses for LCD's which use the Hitachi HD66712U controller chip.
/*
#define LCD_LINE_1_ADDRESS 0x00
#define LCD_LINE_2_ADDRESS 0x20
#define LCD_LINE_3_ADDRESS 0x40
#define LCD_LINE_4_ADDRESS 0x60
*/
//========================================
#define lcd_type 2 // 0=5x7, 1=5x10, 2=2 lines(or more)
int8 lcd_line;
int8 const LCD_INIT_STRING[4] =
{
0x20 | (lcd_type << 2), // Set mode: 4-bit, 2+ lines, 5x8 dots
0xc, // Display on
1, // Clear display
6 // Increment cursor
};
//-------------------------------------
void lcd_send_nibble(int8 nibble)
{
// Note: !! converts an integer expression to a boolean (1 or 0).
output_bit(LCD_DB4, !!(nibble & 1));
output_bit(LCD_DB5, !!(nibble & 2));
output_bit(LCD_DB6, !!(nibble & 4));
output_bit(LCD_DB7, !!(nibble & 8));
delay_cycles(1);
output_high(LCD_E);
delay_us(2);
output_low(LCD_E);
}
//-----------------------------------
// This sub-routine is only called by lcd_read_byte(). It's not a stand-alone routine.
// For example, the R/W signal is set high by lcd_read_byte() before this routine is called.
#ifdef USE_RW_PIN
int8 lcd_read_nibble(void)
{
int8 retval;
// Create bit variables so that we can easily set individual bits in the retval variable.
#bit retval_0 = retval.0
#bit retval_1 = retval.1
#bit retval_2 = retval.2
#bit retval_3 = retval.3
retval = 0;
output_high(LCD_E);
delay_us(1);
retval_0 = input(LCD_DB4);
retval_1 = input(LCD_DB5);
retval_2 = input(LCD_DB6);
retval_3 = input(LCD_DB7);
output_low(LCD_E);
delay_us(1);
return(retval);
}
#endif
//---------------------------------------
// Read a byte from the LCD and return it.
#ifdef USE_RW_PIN
int8 lcd_read_byte(void)
{
int8 low;
int8 high;
output_high(LCD_RW);
delay_cycles(1);
high = lcd_read_nibble();
low = lcd_read_nibble();
return( (high<<4) | low);
}
#endif
//----------------------------------------
// Send a byte to the LCD.
void lcd_send_byte(int8 address, int8 n)
{
output_low(LCD_RS);
#ifdef USE_RW_PIN
while(bit_test(lcd_read_byte(),7)) ;
#else
delay_us(60);
#endif
if(address)
output_high(LCD_RS);
else
output_low(LCD_RS);
delay_cycles(1);
#ifdef USE_RW_PIN
output_low(LCD_RW);
delay_cycles(1);
#endif
output_low(LCD_E);
lcd_send_nibble(n >> 4);
lcd_send_nibble(n & 0xf);
}
//----------------------------
void lcd_init(void)
{
int8 i;
lcd_line = 1;
output_low(LCD_RS);
#ifdef USE_RW_PIN
output_low(LCD_RW);
#endif
output_low(LCD_E);
// Some LCDs require 15 ms minimum delay after power-up. Others require 30 ms.
// I'm going to set it to 35 ms, so it should work with all of them.
delay_ms(35);
for(i=0 ;i < 3; i++)
{
lcd_send_nibble(0x03);
delay_ms(5);
}
lcd_send_nibble(0x02);
for(i=0; i < sizeof(LCD_INIT_STRING); i++)
{
lcd_send_byte(0, LCD_INIT_STRING[i]);
// If the R/W signal is not used, then the busy bit can't be polled.
// One of the init commands takes longer than the hard-coded delay of 50 us,
// so in that case, lets just do a 5 ms delay after all four of them.
#ifndef USE_RW_PIN
delay_ms(5);
#endif
}
}
//----------------------------
void lcd_gotoxy(int8 x, int8 y)
{
int8 address;
switch(y)
{
case 1:
address = LCD_LINE_1_ADDRESS;
break;
case 2:
address = LCD_LINE_2_ADDRESS;
break;
case 3:
address = LCD_LINE_3_ADDRESS;
break;
case 4:
address = LCD_LINE_4_ADDRESS;
break;
default:
address = LCD_LINE_1_ADDRESS;
break;
}
address += x-1;
lcd_send_byte(0, 0x80 | address);
}
//-----------------------------
void lcd_putc(char c)
{
switch(c)
{
case '\f':
lcd_send_byte(0,1);
lcd_line = 1;
delay_ms(2);
break;
case '\n':
lcd_gotoxy(1, ++lcd_line);
break;
case '\b':
lcd_send_byte(0,0x10);
break;
default:
lcd_send_byte(1,c);
break;
}
}
//------------------------------
#ifdef USE_RW_PIN
char lcd_getc(int8 x, int8 y)
{
char value;
lcd_gotoxy(x,y);
// Wait until busy flag is low.
while(bit_test(lcd_read_byte(),7));
output_high(LCD_RS);
value = lcd_read_byte();
output_low(LCD_RS);
return(value);
}
#endif
|
DS18B20 CODE:
| Code: |
float ds1820_read()
{
int8 busy=0, temp1, temp2;
signed int16 temp3;
float result;
onewire_reset();
onewire_write(0xCC);
onewire_write(0x44);
while (busy == 0)
busy = onewire_read();
onewire_reset();
onewire_write(0xCC);
onewire_write(0xBE);
temp1 = onewire_read();
temp2 = onewire_read();
temp3 = make16(temp2, temp1);
result = (float) temp3 / 2.0; //Calculation for DS18S20 with 0.5 deg C resolution
// result = (float) temp3 / 16.0; //Calculation for DS18B20 with 0.1 deg C resolution
delay_ms(200);
return(result);
}
|
1WIRE CODE:
| Code: |
/***********************1Wire Class***********************/
/*Description: This class handles all communication */
/* between the processor and the 1wire */
/* sensors.
/*********************************************************/
/*-------1-wire definitions-------*/
#define ONE_WIRE_PIN PIN_A0
/*******************1-wire communication functions********************/
/************onewire_reset*************************************************/
/*This function initiates the 1wire bus */
/* */
/*PARAMETERS: */
/*RETURNS: */
/*********************************************************************/
void onewire_reset() // OK if just using a single permanently connected device
{
output_low(ONE_WIRE_PIN);
delay_us( 500 ); // pull 1-wire low for reset pulse
output_float(ONE_WIRE_PIN); // float 1-wire high
delay_us( 500 ); // wait-out remaining initialisation window.
output_float(ONE_WIRE_PIN);
}
/*********************** onewire_write() ********************************/
/*This function writes a byte to the sensor.*/
/* */
/*Parameters: byte - the byte to be written to the 1-wire */
/*Returns: */
/*********************************************************************/
void onewire_write(int data)
{
int count;
for (count=0; count<8; ++count)
{
output_low(ONE_WIRE_PIN);
delay_us( 2 ); // pull 1-wire low to initiate write time-slot.
output_bit(ONE_WIRE_PIN, shift_right(&data,1,0)); // set output bit on 1-wire
delay_us( 60 ); // wait until end of write slot.
output_float(ONE_WIRE_PIN); // set 1-wire high again,
delay_us( 2 ); // for more than 1us minimum.
}
}
/*********************** read1wire() *********************************/
/*This function reads the 8 -bit data via the 1-wire sensor. */
/* */
/*Parameters: */
/*Returns: 8-bit (1-byte) data from sensor */
/*********************************************************************/
int onewire_read()
{
int count, data;
for (count=0; count<8; ++count)
{
output_low(ONE_WIRE_PIN);
delay_us( 2 ); // pull 1-wire low to initiate read time-slot.
output_float(ONE_WIRE_PIN); // now let 1-wire float high,
delay_us( 8 ); // let device state stabilise,
shift_right(&data,1,input(ONE_WIRE_PIN)); // and load result.
delay_us( 120 ); // wait until end of read slot.
}
return( data );
} |
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Mike Walne
Joined: 19 Feb 2004
Posts: 1785
Location: Boston Spa UK
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PCM programmer
Joined: 06 Sep 2003
Posts: 21708
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| Posted: Sun Apr 05, 2015 2:26 pm |
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| Quote: | | the sensor reads a temperature of -0.5 ° C. |
According to the ds18B20 data sheet, this reading corresponds to a
hex value of FFF8h. That's mostly '1' bits. Possibly there is a problem
with your connections between the PIC and the ds18b20. |
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temtronic
Joined: 01 Jul 2010
Posts: 9221
Location: Greensville,Ontario
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| Posted: Sun Apr 05, 2015 2:39 pm |
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I used both that PIC and temp sensor years ago for a 'data logger' project for a client so I know it will work !
There is a 'test program' to locate all 1-wire devices, you should run it to confirm that the hardware is operational.
I notice you use the DS1820.c driver. That may NOT be 100% compatible with the DS18B20 devices. Please check the datasheets, I recall there's a 'timing' issue, though it has been 3-5 years since I worked with it.
After that, look at the 1-wire code to read the sensor and confirm that the 'math' is right to convert the sensor data into the proper temperature reading.
also...
you should have a delay_ms(500) BEFORE yo call he lcd init funcxtion. This allows the LCD hardware to 'wakeup' and 'self configure' correctly before the PIC tries to access it.
hth
jay |
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