18B20的1-wire总线search ROM算法实现原理和源代码
1-Wire Search Algorithm | Analog Devices// TMEX API TEST BUILD DECLARATIONS
#define TMEXUTIL
#include "ibtmexcw.h"
long session_handle;
// END TMEX API TEST BUILD DECLARATIONS
// definitions
#define FALSE 0
#define TRUE1
// method declarations
intOWFirst();
intOWNext();
intOWVerify();
void OWTargetSetup(unsigned char family_code);
void OWFamilySkipSetup();
intOWReset();
void OWWriteByte(unsigned char byte_value);
void OWWriteBit(unsigned char bit_value);
unsigned char OWReadBit();
intOWSearch();
unsigned char docrc8(unsigned char value);
// global search state
unsigned char ROM_NO;
int LastDiscrepancy;
int LastFamilyDiscrepancy;
int LastDeviceFlag;
unsigned char crc8;
//--------------------------------------------------------------------------
// Find the 'first' devices on the 1-Wire bus
// Return TRUE: device found, ROM number in ROM_NO buffer
// FALSE : no device present
//
int OWFirst()
{
// reset the search state
LastDiscrepancy = 0;
LastDeviceFlag = FALSE;
LastFamilyDiscrepancy = 0;
return OWSearch();
}
//--------------------------------------------------------------------------
// Find the 'next' devices on the 1-Wire bus
// Return TRUE: device found, ROM number in ROM_NO buffer
// FALSE : device not found, end of search
//
int OWNext()
{
// leave the search state alone
return OWSearch();
}
//--------------------------------------------------------------------------
// Perform the 1-Wire Search Algorithm on the 1-Wire bus using the existing
// search state.
// Return TRUE: device found, ROM number in ROM_NO buffer
// FALSE : device not found, end of search
//
int OWSearch()
{
int id_bit_number;
int last_zero, rom_byte_number, search_result;
int id_bit, cmp_id_bit;
unsigned char rom_byte_mask, search_direction;
// initialize for search
id_bit_number = 1;
last_zero = 0;
rom_byte_number = 0;
rom_byte_mask = 1;
search_result = 0;
crc8 = 0;
// if the last call was not the last one
if (!LastDeviceFlag)
{
// 1-Wire reset
if (!OWReset())
{
// reset the search
LastDiscrepancy = 0;
LastDeviceFlag = FALSE;
LastFamilyDiscrepancy = 0;
return FALSE;
}
// issue the search command
OWWriteByte(0xF0);
// loop to do the search
do
{
// read a bit and its complement
id_bit = OWReadBit();
cmp_id_bit = OWReadBit();
// check for no devices on 1-wire
if ((id_bit == 1) && (cmp_id_bit == 1))
break;
else
{
// all devices coupled have 0 or 1
if (id_bit != cmp_id_bit)
search_direction = id_bit;// bit write value for search
else
{
// if this discrepancy if before the Last Discrepancy
// on a previous next then pick the same as last time
if (id_bit_number < LastDiscrepancy)
search_direction = ((ROM_NO & rom_byte_mask) > 0);
else
// if equal to last pick 1, if not then pick 0
search_direction = (id_bit_number == LastDiscrepancy);
// if 0 was picked then record its position in LastZero
if (search_direction == 0)
{
last_zero = id_bit_number;
// check for Last discrepancy in family
if (last_zero < 9)
LastFamilyDiscrepancy = last_zero;
}
}
// set or clear the bit in the ROM byte rom_byte_number
// with mask rom_byte_mask
if (search_direction == 1)
ROM_NO |= rom_byte_mask;
else
ROM_NO &= ~rom_byte_mask;
// serial number search direction write bit
OWWriteBit(search_direction);
// increment the byte counter id_bit_number
// and shift the mask rom_byte_mask
id_bit_number++;
rom_byte_mask <<= 1;
// if the mask is 0 then go to new SerialNum byte rom_byte_number and reset mask
if (rom_byte_mask == 0)
{
docrc8(ROM_NO);// accumulate the CRC
rom_byte_number++;
rom_byte_mask = 1;
}
}
}
while(rom_byte_number < 8);// loop until through all ROM bytes 0-7
// if the search was successful then
if (!((id_bit_number < 65) || (crc8 != 0)))
{
// search successful so set LastDiscrepancy,LastDeviceFlag,search_result
LastDiscrepancy = last_zero;
// check for last device
if (LastDiscrepancy == 0)
LastDeviceFlag = TRUE;
search_result = TRUE;
}
}
// if no device found then reset counters so next 'search' will be like a first
if (!search_result || !ROM_NO)
{
LastDiscrepancy = 0;
LastDeviceFlag = FALSE;
LastFamilyDiscrepancy = 0;
search_result = FALSE;
}
return search_result;
}
//--------------------------------------------------------------------------
// Verify the device with the ROM number in ROM_NO buffer is present.
// Return TRUE: device verified present
// FALSE : device not present
//
int OWVerify()
{
unsigned char rom_backup;
int i,rslt,ld_backup,ldf_backup,lfd_backup;
// keep a backup copy of the current state
for (i = 0; i < 8; i++)
rom_backup = ROM_NO;
ld_backup = LastDiscrepancy;
ldf_backup = LastDeviceFlag;
lfd_backup = LastFamilyDiscrepancy;
// set search to find the same device
LastDiscrepancy = 64;
LastDeviceFlag = FALSE;
if (OWSearch())
{
// check if same device found
rslt = TRUE;
for (i = 0; i < 8; i++)
{
if (rom_backup != ROM_NO)
{
rslt = FALSE;
break;
}
}
}
else
rslt = FALSE;
// restore the search state
for (i = 0; i < 8; i++)
ROM_NO = rom_backup;
LastDiscrepancy = ld_backup;
LastDeviceFlag = ldf_backup;
LastFamilyDiscrepancy = lfd_backup;
// return the result of the verify
return rslt;
}
//--------------------------------------------------------------------------
// Setup the search to find the device type 'family_code' on the next call
// to OWNext() if it is present.
//
void OWTargetSetup(unsigned char family_code)
{
int i;
// set the search state to find SearchFamily type devices
ROM_NO = family_code;
for (i = 1; i < 8; i++)
ROM_NO = 0;
LastDiscrepancy = 64;
LastFamilyDiscrepancy = 0;
LastDeviceFlag = FALSE;
}
//--------------------------------------------------------------------------
// Setup the search to skip the current device type on the next call
// to OWNext().
//
void OWFamilySkipSetup()
{
// set the Last discrepancy to last family discrepancy
LastDiscrepancy = LastFamilyDiscrepancy;
LastFamilyDiscrepancy = 0;
// check for end of list
if (LastDiscrepancy == 0)
LastDeviceFlag = TRUE;
}
//--------------------------------------------------------------------------
// 1-Wire Functions to be implemented for a particular platform
//--------------------------------------------------------------------------
//--------------------------------------------------------------------------
// Reset the 1-Wire bus and return the presence of any device
// Return TRUE: device present
// FALSE : no device present
//
int OWReset()
{
// platform specific
// TMEX API TEST BUILD
return (TMTouchReset(session_handle) == 1);
}
//--------------------------------------------------------------------------
// Send 8 bits of data to the 1-Wire bus
//
void OWWriteByte(unsigned char byte_value)
{
// platform specific
// TMEX API TEST BUILD
TMTouchByte(session_handle,byte_value);
}
//--------------------------------------------------------------------------
// Send 1 bit of data to teh 1-Wire bus
//
void OWWriteBit(unsigned char bit_value)
{
// platform specific
// TMEX API TEST BUILD
TMTouchBit(session_handle,(short)bit_value);
}
//--------------------------------------------------------------------------
// Read 1 bit of data from the 1-Wire bus
// Return 1 : bit read is 1
// 0 : bit read is 0
//
unsigned char OWReadBit()
{
// platform specific
// TMEX API TEST BUILD
return (unsigned char)TMTouchBit(session_handle,0x01);
}
// TEST BUILD
static unsigned char dscrc_table[] = {
0, 94,188,226, 97, 63,221,131,194,156,126, 32,163,253, 31, 65,
157,195, 33,127,252,162, 64, 30, 95,1,227,189, 62, 96,130,220,
35,125,159,193, 66, 28,254,160,225,191, 93,3,128,222, 60, 98,
190,224,2, 92,223,129, 99, 61,124, 34,192,158, 29, 67,161,255,
70, 24,250,164, 39,121,155,197,132,218, 56,102,229,187, 89,7,
219,133,103, 57,186,228,6, 88, 25, 71,165,251,120, 38,196,154,
101, 59,217,135,4, 90,184,230,167,249, 27, 69,198,152,122, 36,
248,166, 68, 26,153,199, 37,123, 58,100,134,216, 91,5,231,185,
140,210, 48,110,237,179, 81, 15, 78, 16,242,172, 47,113,147,205,
17, 79,173,243,112, 46,204,146,211,141,111, 49,178,236, 14, 80,
175,241, 19, 77,206,144,114, 44,109, 51,209,143, 12, 82,176,238,
50,108,142,208, 83, 13,239,177,240,174, 76, 18,145,207, 45,115,
202,148,118, 40,171,245, 23, 73,8, 86,180,234,105, 55,213,139,
87,9,235,181, 54,104,138,212,149,203, 41,119,244,170, 72, 22,
233,183, 85, 11,136,214, 52,106, 43,117,151,201, 74, 20,246,168,
116, 42,200,150, 21, 75,169,247,182,232, 10, 84,215,137,107, 53};
//--------------------------------------------------------------------------
// Calculate the CRC8 of the byte value provided with the current
// global 'crc8' value.
// Returns current global crc8 value
//
unsigned char docrc8(unsigned char value)
{
// See Application Note 27
// TEST BUILD
crc8 = dscrc_table;
return crc8;
}
//--------------------------------------------------------------------------
// TEST BUILD MAIN
//
int main(short argc, char **argv)
{
short PortType=5,PortNum=1;
int rslt,i,cnt;
// TMEX API SETUP
// get a session
session_handle = TMExtendedStartSession(PortNum,PortType,NULL);
if (session_handle <= 0)
{
printf("No session, %d\n",session_handle);
exit(0);
}
// setup the port
rslt = TMSetup(session_handle);
if (rslt != 1)
{
printf("Fail setup, %d\n",rslt);
exit(0);
}
// END TMEX API SETUP
// find ALL devices
printf("\nFIND ALL\n");
cnt = 0;
rslt = OWFirst();
while (rslt)
{
// print device found
for (i = 7; i >= 0; i--)
printf("%02X", ROM_NO);
printf("%d\n",++cnt);
rslt = OWNext();
}
// find only 0x1A
printf("\nFIND ONLY 0x1A\n");
cnt = 0;
OWTargetSetup(0x1A);
while (OWNext())
{
// check for incorrect type
if (ROM_NO != 0x1A)
break;
// print device found
for (i = 7; i >= 0; i--)
printf("%02X", ROM_NO);
printf("%d\n",++cnt);
}
// find all but 0x04, 0x1A, 0x23, and 0x01
printf("\nFIND ALL EXCEPT 0x10, 0x04, 0x0A, 0x1A, 0x23, 0x01\n");
cnt = 0;
rslt = OWFirst();
while (rslt)
{
// check for incorrect type
if ((ROM_NO == 0x04) || (ROM_NO == 0x1A) ||
(ROM_NO == 0x01) || (ROM_NO == 0x23) ||
(ROM_NO == 0x0A) || (ROM_NO == 0x10))
OWFamilySkipSetup();
else
{
// print device found
for (i = 7; i >= 0; i--)
printf("%02X", ROM_NO);
printf("%d\n",++cnt);
}
rslt = OWNext();
}
// TMEX API CLEANUP
// release the session
TMEndSession(session_handle);
// END TMEX API CLEANUP
}
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