static int
ow_check_crc(romid_t romid)
{
return ow_crc(NULL, NULL, (uint8_t *)&romid, sizeof(romid)) == 0;
}
// NEXT
// The Next function searches for the next device on the 1-wire bus. If
// there are no more devices on the 1-wire then false is returned.
//
unsigned char Next(void) {
unsigned char m = 1; // ROM Bit index
unsigned char n = 0; // ROM Byte index
unsigned char k = 1; // bit mask
unsigned char x = 0;
unsigned char discrepMarker = 0; // discrepancy marker
unsigned char g; // Output bit
unsigned char nxt = FALSE; // return value
int flag;
// reset the 1-wire
flag = ow_reset();
// reset the dowcrc
dowcrc = 0;
// no parts -> return false
if(flag||doneFlag) {
// reset the search
lastDiscrep = 0;
return FALSE;
}
// send SearchROM command
write_byte(0xF0);
// for all eight bytes
do {
x = 0;
if(read_bit()==1) x = 2;
uDelay(120);
if(read_bit()==1) x |= 1;
uDelay(120);
if(x ==3) break;
else {
// all devices coupled have 0 or 1
if(x>0)
// bit write value for search
g = x>>1;
else {
// if this discrepancy is before the last
// discrepancy on a previous Next then pick
// the same as last time
if(m<lastDiscrep) g = ((ROM[n]&k)>0);
else g = (m==lastDiscrep);
// if equal to last pick 1
// if not then pick 0
// if 0 was picked then record
// position with mask k
if (g==0) discrepMarker = m;
}
// isolate bit in ROM[n] with mask k
if(g==1) ROM[n] |= k;
else ROM[n] &= ~k;
// ROM search write
write_bit(g);
// increment bit counter m
m++;
// and shift the bit mask k
k = k<<1;
// if the mask is 0 then go to new ROM
if(k==0) {
// accumulate the CRC
ow_crc(ROM[n]);
// byte n and reset mask
n++;
k++;
}
}
} while(n<8);
// if search was unsuccessful then
// reset the last discrepancy to 0
if(m<65||dowcrc) lastDiscrep=0;
else {
// search was successful, so set lastDiscrep,
// lastOne, nxt;
lastDiscrep = discrepMarker;
doneFlag = (lastDiscrep==0);
// indicates search is not complete yet, more parts remain
nxt = TRUE;
}
return nxt;
}
