/* $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 <grange@openbsd.org> * * 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; }
