//
// You need to use this function to start a search again from the beginning.
// You do not need to do it for the first search, though you could.
//
void OneWire::reset_search()
{
uint8_t i;
searchJunction = -1;
searchExhausted = 0;
for( i = 7; ; i--) {
address[i] = 0;
if ( i == 0) break;
}
}
//
// Perform a search. If this function returns a '1' then it has
// enumerated the next device and you may retrieve the ROM from the
// OneWire::address variable. If there are no devices, no further
// devices, or something horrible happens in the middle of the
// enumeration then a 0 is returned. If a new device is found then
// its address is copied to newAddr. Use OneWire::reset_search() to
// start over.
//
uint8_t OneWire::search(uint8_t *newAddr)
{
uint8_t i;
char lastJunction = -1;
uint8_t done = 1;
if ( searchExhausted) return 0;
if ( !reset()) return 0;
write( 0xf0, 0);
for( i = 0; i < 64; i++) {
uint8_t a = read_bit( );
uint8_t nota = read_bit( );
uint8_t ibyte = i/8;
uint8_t ibit = 1<<(i&7);
if ( a && nota) return 0; // I don't think this should happen, this means nothing responded, but maybe if
// something vanishes during the search it will come up.
if ( !a && !nota) {
if ( i == searchJunction) { // this is our time to decide differently, we went zero last time, go one.
a = 1;
searchJunction = lastJunction;
} else if ( i < searchJunction) { // take whatever we took last time, look in address
if ( address[ ibyte]&ibit) a = 1;
else { // Only 0s count as pending junctions, we've already exhasuted the 0 side of 1s
a = 0;
done = 0;
lastJunction = i;
}
} else { // we are blazing new tree, take the 0
a = 0;
searchJunction = i;
done = 0;
}
lastJunction = i;
}
if ( a) address[ ibyte] |= ibit;
else address[ ibyte] &= ~ibit;
write_bit( a);
}
if ( done) searchExhausted = 1;
for ( i = 0; i < 8; i++) newAddr[i] = address[i];
return 1;
}
#endif
#if ONEWIRE_CRC
// The 1-Wire CRC scheme is described in Maxim Application Note 27:
// "Understanding and Using Cyclic Redundancy Checks with Maxim iButton Products"
//
#if ONEWIRE_CRC8_TABLE
// This table comes from Dallas sample code where it is freely reusable,
// though Copyright (C) 2000 Dallas Semiconductor Corporation
static uint8_t 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};
//
// Compute a Dallas Semiconductor 8 bit CRC. These show up in the ROM
// and the registers. (note: this might better be done without to
// table, it would probably be smaller and certainly fast enough
// compared to all those delayMicrosecond() calls. But I got
// confused, so I use this table from the examples.)
//
uint8_t OneWire::crc8( uint8_t *addr, uint8_t len)
{
uint8_t i;
uint8_t crc = 0;
for ( i = 0; i < len; i++) {
crc = dscrc_table[ crc ^ addr[i] ];
}
return crc;
}
#else
//
// Compute a Dallas Semiconductor 8 bit CRC directly.
//
uint8_t OneWire::crc8( uint8_t *addr, uint8_t len)
{
uint8_t i, j;
uint8_t crc = 0;
for (i = 0; i < len; i++) {
uint8_t inbyte = addr[i];
for (j = 0; j < 8; j++) {
uint8_t mix = (crc ^ inbyte) & 0x01;
crc >>= 1;
if (mix) crc ^= 0x8C;
inbyte >>= 1;
}
}
return crc;
}
#endif
#if ONEWIRE_CRC16
static short oddparity[16] = { 0, 1, 1, 0, 1, 0, 0, 1, 1, 0, 0, 1, 0, 1, 1, 0 };
//
// Compute a Dallas Semiconductor 16 bit CRC. I have never seen one of
// these, but here it is.
//
unsigned short OneWire::crc16(unsigned short *data, unsigned short len)
{
unsigned short i;
unsigned short crc = 0;
for ( i = 0; i < len; i++) {
unsigned short cdata = data[len];
cdata = (cdata ^ (crc & 0xff)) & 0xff;
crc >>= 8;
if (oddparity[cdata & 0xf] ^ oddparity[cdata >> 4]) crc ^= 0xc001;
cdata <<= 6;
crc ^= cdata;
cdata <<= 1;
crc ^= cdata;
}
return crc;
}
#endif
#endif