svn commit: r338574 - head/share/man/man4/man4.arm
Oleksandr Tymoshenko
gonzo at FreeBSD.org
Mon Sep 10 22:48:27 UTC 2018
Author: gonzo
Date: Mon Sep 10 22:48:26 2018
New Revision: 338574
URL: https://svnweb.freebsd.org/changeset/base/338574
Log:
[bcm283x_pwm] Add documentation for the second PWM channel
Document sysctls for the second PWM channel added in r335855
Also fix some minor style issues and a typo.
Approved by: re (gjb)
Submitted by: bobf at mrp3.com
Reviewed by: 0mp
Differential Revision: https://reviews.freebsd.org/D17084
Modified:
head/share/man/man4/man4.arm/bcm283x_pwm.4
Modified: head/share/man/man4/man4.arm/bcm283x_pwm.4
==============================================================================
--- head/share/man/man4/man4.arm/bcm283x_pwm.4 Mon Sep 10 20:46:17 2018 (r338573)
+++ head/share/man/man4/man4.arm/bcm283x_pwm.4 Mon Sep 10 22:48:26 2018 (r338574)
@@ -26,7 +26,7 @@
.\"
.\" $FreeBSD$
.\"
-.Dd January 22, 2017
+.Dd September 10, 2018
.Dt BCM283X_PWM 4
.Os
.Sh NAME
@@ -38,43 +38,56 @@
.Sh DESCRIPTION
The
.Nm
-driver provides access to the PWM engine on GPIO12 of Rpi 2 and 3 hardware.
+driver provides access to the PWM engine on GPIO12 of Raspberry Pi 2 and 3 hardware.
.Pp
The PWM hardware is controlled via the
.Xr sysctl 8
interface:
.Bd -literal
dev.pwm.0.mode: 1
+dev.pwm.0.mode2: 1
dev.pwm.0.freq: 125000000
dev.pwm.0.ratio: 2500
+dev.pwm.0.ratio2: 2500
dev.pwm.0.period: 10000
+dev.pwm.0.period2: 10000
dev.pwm.0.pwm_freq: 12500
+dev.pwm.0.pwm_freq2: 12500
.Ed
-.Bl -tag -width ".Va dev.pwm.0.mode"
-.It Va dev.pwm.0.mode
+.Bl -tag -width ".Va dev.pwm"
+.It Va dev.pwm.0.mode , dev.pwm.0.mode2
+PWM Mode for channels 1 and 2.
Three modes exist, 0=off, 1=PWM, 2=N/M.
The N/M mode is a first order delta-sigma mode, which makes a quite
handy DAC output with a trivial RC lowpass filter.
.Pp
.It Va dev.pwm.0.freq
The input frequency to the PWM hardware in Hz.
-Minmum frequency is 123 kHz, maximum frequency is 125 MHz.
-.It Va dev.pwm.0.period
+Applies to both channels 1 and 2.
+Minimum frequency is 123 kHz, maximum frequency is 125 MHz.
+.It Va dev.pwm.0.period , dev.pwm.0.period2
The period length in cycles.
-In PWM mode, the output frequency will be
+In PWM mode, the output frequencies will be
(
.Va dev.pwm.0.freq
/
-.Va dev.pwm.0.period .
-)
-In N/M mode this is the 'M'
-.It Va dev.pwm.0.ratio
-The "on" period in cycles.
+.Va dev.pwm.period
+) and (
+.Va dev.pwm.0.freq2
+/
+.Va dev.pwm.0.period2
+).
+In N/M mode this is the 'M'.
+.It Va dev.pwm.0.ratio , dev.pwm.0.ratio2
+The "on" period in cycles for PWM channels 1 and 2.
In PWM mode, to get a 25% dutycycle, set this to 25% of
-.Va dev.pwm.0.period .
-In N/M mode this is the 'N'
-.It Va dev.pwm.0.pwm_freq
-The calculated PWM output frequency in PWM mode.
+.Va dev.pwm.0.period
+or
+.Va dev.pwm.0.period2 ,
+as appropriate.
+In N/M mode this is the 'N'.
+.It Va dev.pwm.0.pwm_freq , dev.pwm.0.pwm_freq2
+The calculated PWM output frequencies in PWM mode, for channels 1 and 2.
.El
.Pp
.Sh NOTES
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