Differential D22108 Diff 63539 sys/dev/ow/owc_gpiobus.c

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sys/dev/ow/owc_gpiobus.c

Show First 20 Lines • Show All 273 Lines • ▼ Show 20 Lines	owc_gpiobus_read_data(device_t dev, struct ow_timing t, int bit)
int error, sample;		int error, sample;
sbintime_t then, now;		sbintime_t then, now;

sc = device_get_softc(dev);		sc = device_get_softc(dev);
error = GETBUS(sc);		error = GETBUS(sc);
if (error != 0)		if (error != 0)
return (error);		return (error);

		critical_enter();

/* Force low for t_lowr microseconds */		/* Force low for t_lowr microseconds */
then = sbinuptime();		then = sbinuptime();
OUTPIN(sc);		OUTPIN(sc);
LOW(sc);		LOW(sc);
DELAY(t->t_lowr);		DELAY(t->t_lowr);

/*		/*
* Slave is supposed to hold the line low for t_rdv microseconds for 0		* Slave is supposed to hold the line low for t_rdv microseconds for 0
* and immediately float it high for a 1. This is measured from the		* and immediately float it high for a 1. This is measured from the
* master's pushing the line low.		* master's pushing the line low.
*/		*/
INPIN(sc);		INPIN(sc);
critical_enter();
do {		do {
now = sbinuptime();		now = sbinuptime();
GETPIN(sc, &sample);		GETPIN(sc, &sample);
} while (sbttous(now - then) < t->t_rdv + 2 && sample == 0);		} while (now - then < (t->t_rdv + 2) * SBT_1US && sample == 0);
critical_exit();		critical_exit();

if (sbttons(now - then) < t->t_rdv * 1000)		if (now - then < t->t_rdv * SBT_1US)
*bit = 1;		*bit = 1;
else		else
*bit = 0;		*bit = 0;

/* Wait out the rest of t_slot */		/* Wait out the rest of t_slot */
do {		do {
now = sbinuptime();		now = sbinuptime();
} while ((now - then) / SBT_1US < t->t_slot);		} while (now - then < (t->t_slot + 2 * t->t_rec) * SBT_1US);

RELBUS(sc);		RELBUS(sc);

return (error);		return (error);
}		}

/*		/*
* RESET AND PRESENCE PULSE (see owll_if.m for timings) From Figure 4-4 AN-937		* RESET AND PRESENCE PULSE (see owll_if.m for timings) From Figure 4-4 AN-937
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