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Dallas DS18s20 driver

 
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omallicha



Joined: 15 Aug 2007
Posts: 5

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Dallas DS18s20 driver
PostPosted: Thu Feb 07, 2008 4:48 am     Reply with quote

this is a working driver for the DS18s20 temperature sensor.
Code:
[/**************************
* Driver for Maxim DS18S20
* Version 2.0
* Date: 30/05/2007
* Using CCS C Compiler
*

***************************/

// Define the data pins from microcontroler

//#define ds18s20_dq_sensor1   PIN_c1



// ROM Commands
#define DS18S20_READ_ROM   0x33
#define DS18S20_MATCH_ROM   0x55
#define DS18S20_SKIP_ROM   0xCC


// Function Commands
#define DS18S20_CONVERT_T   0x44
#define DS18S20_READ_SCRATCHPAD   0xBE


// For memorize the CRC value
int ds18s20_crc;


// Actualize ds18s20_crc after insert a bit
void ds18s20_actualizeCRCbit(int1 valueBit)
{
   int1 xor_crcBeforeBit0_Input;
   byte crcBefore;

   crcBefore = ds18s20_crc;

   // Calculation xor_crcBeforeBit0_Input
   if ((crcBefore & 0x01) == valueBit) xor_crcBeforeBit0_Input = 0;
   else   xor_crcBeforeBit0_Input = 1;
   

   // Calculation crcBit0
   if ((crcBefore & 0x02) > 0) ds18s20_crc |= 0x01;
   else   ds18s20_crc &= 0xFE;

   // Calculation crcBit1
   if ((crcBefore & 0x04) > 0) ds18s20_crc |= 0x02;
   else   ds18s20_crc &= 0xFD;

   // Calculation crcBit2
   if ((crcBefore & 0x08) > 0)
   {
      if (xor_crcBeforeBit0_Input == 0) ds18s20_crc |= 0x04;
      else   ds18s20_crc &= 0xFB;
   }
   else
   {
      if (xor_crcBeforeBit0_Input == 1) ds18s20_crc |= 0x04;
      else   ds18s20_crc &= 0xFB;
   }

   // Calculation crcBit3
   if ((crcBefore & 0x10) > 0)
   {
      if (xor_crcBeforeBit0_Input == 0) ds18s20_crc |= 0x08;
      else   ds18s20_crc &= 0xF7;
   }
   else
   {
      if (xor_crcBeforeBit0_Input == 1) ds18s20_crc |= 0x08;
      else   ds18s20_crc &= 0xF7;
   }
   
   // Calculation crcBit4
   if ((crcBefore & 0x20) > 0) ds18s20_crc |= 0x10;
   else   ds18s20_crc &= 0xEF;

   // Calculation crcBit5
   if ((crcBefore & 0x40) > 0) ds18s20_crc |= 0x20;
   else   ds18s20_crc &= 0xDF;

   // Calculation crcBit6
   if ((crcBefore & 0x80) > 0) ds18s20_crc |= 0x40;
   else   ds18s20_crc &= 0xBF;

   // Calculation crcBit7
   if (xor_crcBeforeBit0_Input == 1) ds18s20_crc |= 0x80;
   else   ds18s20_crc &= 0x7F;
}


// Inicialize the line
// Returns 0 if exists one or more sensors in the line
int1 ds18s20_inicializeLine()
{
   int1 ack;
   
   ack = 0;

   output_float(ds18s20_dq_sensor1);
   delay_ms(1);

         output_bit(ds18s20_dq_sensor1, 0);
         delay_us(600);

         output_float(ds18s20_dq_sensor1);
         delay_us(100);
         ack = input(ds18s20_dq_sensor1);
         delay_us(500);


   return (ack);
}



// Write bit in the line
void ds18s20_writeBit(int1 valueBit)
{
   
   if (valueBit == 0)
   {
   
            output_bit(ds18s20_dq_sensor1, 0);
            delay_us(110);
            output_float(ds18s20_dq_sensor1);
            delay_us(100);

   
   }
   else
   {


            output_bit(ds18s20_dq_sensor1, 0);
            delay_us(10);
            output_float(ds18s20_dq_sensor1);
            delay_us(200);

   }
   
}



// Read bit in the line
int1 ds18s20_readBit()
{
   int1 readBit;


         output_bit(ds18s20_dq_sensor1, 0);
         delay_us(5);
         output_float(ds18s20_dq_sensor1);
         delay_us(15);
         readBit = input(ds18s20_dq_sensor1);
         delay_us(100);


   ds18s20_actualizeCRCbit(readBit);   // Actualize CRC
   return(readBit);
}




// Write byte in the line
void ds18s20_writeByte(int8 valueByte)
{
   int i,mask;

   mask = 0x01;
   for (i=0; i<8; i++)
   {
      if((valueByte & mask) > 0)  ds18s20_writeBit(1);
      else ds18s20_writeBit(0);
      mask = mask << 1;
   }
}


// Read byte in the line
int8 ds18s20_readByte()
{
   int8 i,valueByte = 0;
   
   const int8 mask0 = 0x00;
   const int8 mask1 = 0x80;

   for (i=0; i<8; i++)
   {
      valueByte = valueByte >> 1;
      if (ds18s20_readBit() == 1) valueByte |= mask1;
       else valueByte |= mask0;
   }
   return (valueByte);
}   



// Sends the command Read Scratchpad
int1 ds18s20_sendsCommandReadScratchpad()
{
   int1 ack;

   ack = ds18s20_inicializeLine();
   if (ack == 1)
   {
      return (1);
   }

   ds18s20_writeByte(DS18S20_SKIP_ROM);

   ds18s20_writeByte(DS18S20_READ_SCRATCHPAD);

   return (0);
}


// Reads the value of temperature (resolution 1şC)
int8 ds18s20_readTemperatureLowResolution()
{
   int8 valueTemperature;


   if (ds18s20_sendsCommandReadScratchpad() == 1)
   {
      return (100);
   }

   ds18s20_crc = 0;
   valueTemperature = ds18s20_readByte()/2;
   ds18s20_readByte();
   ds18s20_readByte();
   ds18s20_readByte();
   ds18s20_readByte();
   ds18s20_readByte();
   ds18s20_readByte();
   ds18s20_readByte();
   ds18s20_readByte();

   // Error on value read
   if (ds18s20_crc != 0)
   {
      return (100);
   }

   return (valueTemperature);
}


// Reads the value of temperature (resolution 0.1şC)
int16 ds18s20_readTemperatureHighResolution()
{
   float temperature,aux;
   int8 temp_read, count_per_c, count_remain;


   if (ds18s20_sendsCommandReadScratchpad() == 1)
   {
      return (0);
   }

   ds18s20_crc = 0;
   temp_read = ds18s20_readByte();
   ds18s20_readByte();
   ds18s20_readByte();
   ds18s20_readByte();
   ds18s20_readByte();
   ds18s20_readByte();
   count_remain = ds18s20_readByte();
   count_per_c = ds18s20_readByte();
   ds18s20_readByte();

   if (ds18s20_crc != 0)
   {
      return (0);
   }

   temp_read = temp_read >> 1;
   temp_read &= 0x7F;
   temperature = temp_read - 0.25;
   aux = count_per_c - count_remain;
   aux /= count_per_c;
   temperature += aux;
   temperature *= 10;
   
   return (temperature);
}


// Send a command ConvertT for one sensor
// Need to wait for about one second before read the value
int1 ds18s20_startConvert()
{
   int1 ack;

   ack = ds18s20_inicializeLine();
   if (ack == 1)
   {
      return (1);
   }

   ds18s20_writeByte(DS18S20_SKIP_ROM);
   ds18s20_writeByte(DS18S20_CONVERT_T);
   
   return (0);
}
]
Poun44



Joined: 12 Feb 2008
Posts: 1

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PostPosted: Tue Feb 12, 2008 2:24 am     Reply with quote

Does it works with a PIC16F877 ?
Because it doesn't work, Can you help me?
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