1.\" 2.\" SPDX-License-Identifier: BSD-2-Clause 3.\" 4.\" Copyright (c) 2017 Poul-Henning Kamp <phk@FreeBSD.org> 5.\" All rights reserved. 6.\" 7.\" Redistribution and use in source and binary forms, with or without 8.\" modification, are permitted provided that the following conditions 9.\" are met: 10.\" 1. Redistributions of source code must retain the above copyright 11.\" notice, this list of conditions and the following disclaimer. 12.\" 2. Redistributions in binary form must reproduce the above copyright 13.\" notice, this list of conditions and the following disclaimer in the 14.\" documentation and/or other materials provided with the distribution. 15.\" 16.\" THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS OR 17.\" IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES 18.\" OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED. 19.\" IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT, INDIRECT, 20.\" INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT 21.\" NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, 22.\" DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY 23.\" THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT 24.\" (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF 25.\" THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE. 26.\" 27.Dd September 10, 2018 28.Dt BCM283X_PWM 4 29.Os 30.Sh NAME 31.Nm bcm283x_pwm 32.Nd bcm283x_pwm - driver for Raspberry Pi 2/3 PWM 33.Sh SYNOPSIS 34.Cd "kldload bcm283x_clkman" 35.Cd "kldload bcm283x_pwm" 36.Sh DESCRIPTION 37The 38.Nm 39driver provides access to the PWM engine on GPIO12 of Raspberry Pi 2 and 3 hardware. 40.Pp 41The PWM hardware is controlled via the 42.Xr sysctl 8 43interface: 44.Bd -literal 45dev.pwm.0.mode: 1 46dev.pwm.0.mode2: 1 47dev.pwm.0.freq: 125000000 48dev.pwm.0.ratio: 2500 49dev.pwm.0.ratio2: 2500 50dev.pwm.0.period: 10000 51dev.pwm.0.period2: 10000 52dev.pwm.0.pwm_freq: 12500 53dev.pwm.0.pwm_freq2: 12500 54.Ed 55.Bl -tag -width ".Va dev.pwm" 56.It Va dev.pwm.0.mode , dev.pwm.0.mode2 57PWM Mode for channels 1 and 2. 58Three modes exist, 0=off, 1=PWM, 2=N/M. 59The N/M mode is a first order delta-sigma mode, which makes a quite 60handy DAC output with a trivial RC lowpass filter. 61.Pp 62.It Va dev.pwm.0.freq 63The input frequency to the PWM hardware in Hz. 64Applies to both channels 1 and 2. 65Minimum frequency is 123 kHz, maximum frequency is 125 MHz. 66.It Va dev.pwm.0.period , dev.pwm.0.period2 67The period length in cycles. 68In PWM mode, the output frequencies will be 69( 70.Va dev.pwm.0.freq 71/ 72.Va dev.pwm.period 73) and ( 74.Va dev.pwm.0.freq2 75/ 76.Va dev.pwm.0.period2 77). 78In N/M mode this is the 'M'. 79.It Va dev.pwm.0.ratio , dev.pwm.0.ratio2 80The "on" period in cycles for PWM channels 1 and 2. 81In PWM mode, to get a 25% dutycycle, set this to 25% of 82.Va dev.pwm.0.period 83or 84.Va dev.pwm.0.period2 , 85as appropriate. 86In N/M mode this is the 'N'. 87.It Va dev.pwm.0.pwm_freq , dev.pwm.0.pwm_freq2 88The calculated PWM output frequencies in PWM mode, for channels 1 and 2. 89.El 90.Pp 91.Sh NOTES 92Currently the 93.Nm 94driver ignores the 'status="disabled"' flag in the DTB, assuming that 95if you load the driver, you want it to work. 96.Sh SEE ALSO 97.Xr sysctl 8 98.Sh HISTORY 99The 100.Nm 101driver first appeared in 102.Fx 12.0 . 103.Sh AUTHORS 104.An -nosplit 105The 106.Nm 107driver and this manual page were written by 108.An Poul-Henning Kamp Aq Mt phk@FreeBSD.org . 109