Date: Wed, 30 Oct 2019 15:15:53 +0000 (UTC) From: Andriy Gapon <avg@FreeBSD.org> To: src-committers@freebsd.org, svn-src-all@freebsd.org, svn-src-head@freebsd.org Subject: svn commit: r354180 - head/sys/dev/ow Message-ID: <201910301515.x9UFFrI4084905@repo.freebsd.org>
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Author: avg Date: Wed Oct 30 15:15:53 2019 New Revision: 354180 URL: https://svnweb.freebsd.org/changeset/base/354180 Log: ow(4): increase regular mode recovery time, t_rec, to 15 us Previously we used the minimal value of 1 us and it was really tight. Application Note 3829 has a table describing recommended t_rec values for various bus voltages, temperature conditions and numbers of slave devices. The new value decreases the maximum possible data rate from 16.3 Kbit/s to 13.3 Kbit/s, but it allows for up to four slaves on a 3.3V bus (under room temperature). References: - Maxim Integrated Application Note 3829 Determining the Recovery Time for Multiple-Slave 1-Wire(R) Networks - Maxim Integrated Application Note 937 Book of iButton Standards Discussed with: imp (D22108) MFC after: 3 weeks Modified: head/sys/dev/ow/ow.c Modified: head/sys/dev/ow/ow.c ============================================================================== --- head/sys/dev/ow/ow.c Wed Oct 30 14:05:50 2019 (r354179) +++ head/sys/dev/ow/ow.c Wed Oct 30 15:15:53 2019 (r354180) @@ -80,7 +80,7 @@ static struct ow_timing timing_regular = { .t_low0 = 60, /* really 60 to 120 */ .t_low1 = 1, /* really 1 to 15 */ .t_release = 45, /* <= 45us */ - .t_rec = 1, /* at least 1us */ + .t_rec = 15, /* at least 1us */ .t_rdv = 15, /* 15us */ .t_rstl = 480, /* 480us or more */ .t_rsth = 480, /* 480us or more */
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