omallicha
Joined: 15 Aug 2007
Posts: 5
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| Dallas DS18s20 driver |
 Posted: Thu Feb 07, 2008 4:48 am |
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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);
}
] |
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