/* $NetBSD: onewire_bitbang.c,v 1.2 2019/11/30 23:04:12 ad Exp $ */
/* $OpenBSD: onewire_bitbang.c,v 1.1 2006/03/04 16:27:03 grange Exp $ */
/*-
* Copyright (c) 2019 The NetBSD Foundation, Inc.
* All rights reserved.
*
* This code is derived from software contributed to The NetBSD Foundation
* by Andrew Doran.
*
* Redistribution and use in source and binary forms, with or without
* modification, are permitted provided that the following conditions
* are met:
* 1. Redistributions of source code must retain the above copyright
* notice, this list of conditions and the following disclaimer.
* 2. Redistributions in binary form must reproduce the above copyright
* notice, this list of conditions and the following disclaimer in the
* documentation and/or other materials provided with the distribution.
*
* THIS SOFTWARE IS PROVIDED BY THE NETBSD FOUNDATION, INC. AND CONTRIBUTORS
* ``AS IS'' AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED
* TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR
* PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE FOUNDATION OR CONTRIBUTORS
* BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR
* CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF
* SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS
* INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN
* CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
* ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
* POSSIBILITY OF SUCH DAMAGE.
*/
/*
* Copyright (c) 2006 Alexander Yurchenko <
[email protected]>
*
* Permission to use, copy, modify, and distribute this software for any
* purpose with or without fee is hereby granted, provided that the above
* copyright notice and this permission notice appear in all copies.
*
* THE SOFTWARE IS PROVIDED "AS IS" AND THE AUTHOR DISCLAIMS ALL WARRANTIES
* WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF
* MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR
* ANY SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES
* WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS, WHETHER IN AN
* ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING OUT OF
* OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE.
*/
#include <sys/cdefs.h>
__KERNEL_RCSID(0, "$NetBSD: onewire_bitbang.c,v 1.2 2019/11/30 23:04:12 ad Exp $");
/*
* 1-Wire bus bit-banging routines.
*/
#include <sys/param.h>
#include <sys/systm.h>
#include <sys/device.h>
#include <sys/proc.h>
#include <dev/onewire/onewirevar.h>
/*
* Reset the bus. Sequence from DS18B20 datasheet:
*
* 1: Master pulls bus low for a minimum of 480us.
* 2: Bus pulled up by resistor. DS18B20 detects rising edge, waits 15-60us.
* 3: DS18B20 pulls bus low for 60-240us.
* 4: Bus pulled up by resistor. Master must wait at least 450us.
*
* 111111111112222233333444444444
*
* Vpu | +-+ +----->
* | / | /
* GND +----------+ +-----+
*/
int
onewire_bb_reset(const struct onewire_bbops *ops, void *arg)
{
int s, rv, i;
rv = 0;
s = splhigh();
ops->bb_tx(arg);
ops->bb_set(arg, 0);
delay(500);
ops->bb_set(arg, 1);
ops->bb_rx(arg);
for (i = 0; i < 240 / 5; i++) {
delay(5);
if ((rv = ops->bb_get(arg)) == 0)
break;
}
splx(s);
/*
* After a bus reset, we must wait for at least 450us before any
* further device access. There is no upper bound on this time, so
* rather than burning CPU, sleep for 1 tick.
*/
KASSERT(2001 > hz);
(void)kpause("owreset", false, 1, NULL);
/*
* With a push-pull GPIO, bring the bus high to supply
* parasite-powered devices. With either PP or open drain,
* past this point on entry to onewire_bb_write_bit() and
* onewire_bb_read_bit() we assume that the line is set to
* output and not being held low.
*/
s = splhigh();
ops->bb_tx(arg);
ops->bb_set(arg, 1);
splx(s);
return rv;
}
/*
* Onewire bit write.
*
* Method: pull the bus low. Then let the pull up resistor settle the bus.
* ZERO is signalled by the bus being held low for minimum 60us.
* ONE is signalled by the hold being much shorter (minimum 1us).
*
* In any eventuality, pad the entire transaction to the minimum 60us, plus
* an additional bit of recovery time before the next transaction
*/
void
onewire_bb_write_bit(const struct onewire_bbops *ops, void *arg, int value)
{
int s, d1, d2;
if (value) {
d1 = 2;
d2 = 62;
} else {
d1 = 62;
d2 = 2;
}
s = splhigh();
ops->bb_set(arg, 0);
delay(d1);
ops->bb_set(arg, 1);
splx(s);
/* Timing no longer critical. */
delay(d2);
}
/*
* Onewire bit read.
*
* Method: pull the bus low for at least 1us. Then let the pull up resistor
* settle the bus. ZERO is signalled by the bus being pulled low again by
* the slave at some point between 15-45us of transaction start. ONE is
* signalled by the bus not being pulled low.
*
* In any eventuality, pad the entire transaction to the minimum 60us, plus
* an additional bit of recovery time before the next transaction.
*/
int
onewire_bb_read_bit(const struct onewire_bbops *ops, void *arg)
{
int s, rv, us;
s = splhigh();
ops->bb_set(arg, 0);
delay(2);
ops->bb_set(arg, 1);
ops->bb_rx(arg);
for (us = 62; us >= 60 - 45; us -= 5) {
delay(5);
if ((rv = ops->bb_get(arg)) == 0) {
break;
}
}
splx(s);
/* Timing no longer critical, and no further need to poll. */
if (us > 0) {
delay(us);
}
ops->bb_tx(arg);
ops->bb_set(arg, 1);
return rv;
}
