u8 ow_reset()
{
u8 flag;
u8 result = 0;
init_onewire();
ow_assert_low();
delay_us(480);
flag = disable_interrupts();
ow_bus_float();
delay_us(66);
if (ow_read())
{
/* No presence pulse */
result = 1;
}
delay_us(414);
if (result==0 && ow_read() == 0)
{
/* bus is shorted */
result = 2;
}
restore_flags(flag);
return result;
}
int8_t ow_temp_power(ow_rom_code_t *rom)
{
#if ONEWIRE_BUSCOUNT > 1
uint8_t busmask = 1 << (ONEWIRE_STARTPIN); // FIXME: currently only on 1st bus
#else
uint8_t busmask = ONEWIRE_BUSMASK;
#endif
int8_t ret;
if (rom == NULL)
ret = ow_skip_rom();
else {
if (!ow_temp_sensor(rom))
return -2;
ret = ow_match_rom(rom);
}
if (ret < 0)
return ret;
/* transmit command byte */
ow_write_byte(busmask, OW_FUNC_READ_POWER);
return (int8_t)(ow_read(busmask));
}
u8 ow_bit_io(u8 b)
{
u8 flags;
flags = disable_interrupts();
ow_assert_low();
delay_us(1);
if (b)
{
ow_bus_float();
}
delay_us(14);
b = ow_read();
delay_us(45);
ow_bus_float();
restore_flags(flags);
return b;
}
static int8_t
ow_read_bit(uint8_t i)
{
uint8_t bit;
/* >= 1usec recovery time. */
ow_release();
_delay_us(1);
/* >= 1 usec pull low to start read slot. */
/* The read slot is time critical to a few usec, so disable interrupts. */
cli();
ow_low();
_delay_us(1);
ow_release();
/*
We must read the bus within at most 15 usec from pulling the bus low.
The later we read, the more margin. But let's keep a couple usec to account
for delays outside of _delay_us().
*/
_delay_us(12);
bit= ow_read();
sei();
if ((i % 8) == 0)
ow_read_buf[i / 8] = 0;
if (bit)
ow_read_buf[i / 8] |= (1 << (i % 8));
/* Total read slot >= 60 usec. */
ow_delay_us(60-1-12);
return 0;
}
uint8_t noinline ow_read_byte(uint8_t busmask)
{
uint8_t data = 0;
for (uint8_t i = 0; i < 8; i++) {
data |= (uint8_t)(ow_read(busmask) << i);
}
return data;
}
static int8_t
ow_init(uint8_t i)
{
if (i == 0)
{
/* Reset pulse: low for >= 480 usec. */
ow_low();
ow_delay_us(480);
}
else if (i == 1)
{
/* Presence detect 60 usec <= T <= 240 usec. */
ow_release();
ow_delay_us(60);
}
else
{
/* Total presence pulse 480 usec. */
ow_presence= !ow_read();
ow_delay_us(480-60);
}
return 0;
}
uint8_t ds18b20_ping(void)
{
uint8_t i;
uint8_t n = 0;
int16_t v;
if (!ow_read())
return 0;
for (i = 0; i < ow_n_addrs; i++) {
if (ow_addr(i)[0] == DS18B20_FAMILY_CODE) {
ow_reset();
ow_match_rom(i);
ow_write_byte(DS18B20_CMD_READ_SCRATCHPAD);
v = ow_read_byte();
v |= ow_read_byte() << 8;
if (ds18b20_temps[n]) {
ds18b20_temps[n] -= ds18b20_temps[n] >> 4;
ds18b20_temps[n] += v;
} else {
ds18b20_temps[n] = v << 4;
}
}
int8_t ow_temp_start_convert(ow_rom_code_t *rom, uint8_t wait)
{
int8_t ret;
if (rom == NULL)
ret = ow_skip_rom();
else {
/* check for known family code */
if (!ow_temp_sensor(rom))
return -2;
ret = ow_match_rom(rom);
}
if (ret < 0)
return ret;
/* transmit command byte */
ow_write_byte(ONEWIRE_BUSMASK, OW_FUNC_CONVERT);
OW_CONFIG_OUTPUT(ONEWIRE_BUSMASK);
OW_HIGH(ONEWIRE_BUSMASK);
if (!wait)
return 0;
_delay_ms(800); /* The specification say, that we have to wait at
least 500ms in parasite mode to wait for the
end of the conversion. 800ms works more reliably */
while(!ow_read(ONEWIRE_BUSMASK));
return 1;
}
/* high-level functions */
int8_t noinline ow_search_rom(uint8_t busmask, uint8_t first)
{
/* reset discover state machine */
if (first) {
ow_global.last_discrepancy = -1;
/* reset rom code */
for (uint8_t i = 0; i < 8; i++)
ow_global.current_rom.bytewise[i] = 0;
} else {
/* if last_discrepancy is below zero, discovery is done */
if (ow_global.last_discrepancy < 0)
return 0;
}
int8_t discrepancy = -1;
/* reset the bus */
if (!reset_onewire(busmask))
return -1;
/* transmit command byte */
ow_write_byte(busmask, OW_ROM_SEARCH_ROM);
for (uint8_t i = 0; i <64; i++) {
/* read bits */
uint8_t bit1 = ow_read(busmask);
uint8_t bits = (uint8_t)((ow_read(busmask) << 1) | bit1);
if (bits == 3) {
/* no devices, just return */
return 0;
} else if (bits == 0) {
if (i == ow_global.last_discrepancy) {
/* set one */
ow_set_address_bit(&ow_global.current_rom, i, 1);
/* transmit one next time */
bit1 = 1;
} else if (i > ow_global.last_discrepancy) {
/* set zero */
ow_set_address_bit(&ow_global.current_rom, i, 0);
discrepancy = (int8_t)i;
} else {
uint8_t rom_bit = (uint8_t)(ow_global.current_rom.bytewise[i / 8] & _BV(i % 8));
if (rom_bit == 0)
discrepancy = (int8_t)i;
/* transmit last bit next time */
bit1 = rom_bit;
}
} else {
/* normal case, no discrepancy */
ow_set_address_bit(&ow_global.current_rom, i, bit1);
}
OW_CONFIG_OUTPUT(busmask);
/* select next bit */
ow_write(busmask, bit1);
}
ow_global.last_discrepancy = discrepancy;
/* new device discovered */
return 1;
}
