uint8_t noinline ow_read(uint8_t busmask)
{
/* a read timeslot is sent by holding the data line low for
* 1us, then wait approximately 14us, then sample data and
* wait */
/* this is also used as ow_write_1, as the only difference
* is that the return value is discarded */
OW_CONFIG_OUTPUT(busmask);
OW_LOW(busmask);
_delay_loop_2(OW_READ_TIMEOUT_1);
OW_HIGH(busmask);
OW_CONFIG_INPUT(busmask);
_delay_loop_2(OW_READ_TIMEOUT_2);
/* sample data now */
uint8_t data = (uint8_t)(OW_GET_INPUT(busmask) > 0);
/* wait for remaining slot time */
_delay_loop_2(OW_READ_TIMEOUT_3);
OW_CONFIG_OUTPUT(busmask);
return data;
}
void noinline ow_write_0(uint8_t busmask)
{
/* a write 0 timeslot is initiated by holding the data line low for
* approximately 80us */
OW_LOW(busmask);
_delay_loop_2(OW_WRITE_0_TIMEOUT);
OW_HIGH(busmask);
}
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;
}
uint8_t noinline
reset_onewire(uint8_t busmask)
{
uint8_t data1, data2;
ATOMIC_BLOCK(ATOMIC_RESTORESTATE)
{
/* pull bus low */
OW_CONFIG_OUTPUT(busmask);
OW_LOW(busmask);
/* wait 480us */
_delay_loop_2(OW_RESET_TIMEOUT_1);
/* release bus */
OW_CONFIG_INPUT(busmask);
/* wait 60us (maximal pause) + 30 us (half minimum pulse) */
_delay_loop_2(OW_RESET_TIMEOUT_2);
/* sample data */
data1 = OW_GET_INPUT(busmask);
/* wait 390us */
_delay_loop_2(OW_RESET_TIMEOUT_3);
/* sample data again */
data2 = OW_GET_INPUT(busmask);
/* if first sample is low and second sample is high, at least one device
* is attached to this bus */
OW_HIGH(busmask);
OW_CONFIG_OUTPUT(busmask);
}
return (uint8_t) (~data1 & data2 & busmask);
}
