BCM283X_PWM(4)

📦 version 15.1, in freebsd 14.5, freebsd 15.1

okay so bestie, welcome to BCM283X_PWM(4), straight out of the arm Kernel Interfaces Manual — it's the Raspberry Pi PWM driver page and it's lowkey iconic. 💖

🌸 NAME 🌸

bcm283x_pwm — driver for Raspberry Pi 2/3 PWM, periodt. ✨

🦋 SYNOPSIS 🦋

kldload bcm283x_clkman
kldload bcm283x_pwm

✨ DESCRIPTION ✨

The bcm283x_pwm driver gives you access to the PWM engine on GPIO12 of Raspberry Pi 2 and 3 hardware. no cap, that's the whole vibe. 🎀

The PWM hardware is controlled via the sysctl(8) interface:

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
  • 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. 🫶
  • dev.pwm.0.freq — The input frequency to the PWM hardware in Hz. Applies to both channels 1 and 2. Minimum frequency is 123 kHz, maximum frequency is 125 MHz. ⭐
  • dev.pwm.0.period, dev.pwm.0.period2 — The period length in cycles. In PWM mode, the output frequencies will be ( dev.pwm.0.freq / dev.pwm.period ) and ( dev.pwm.0.freq2 / dev.pwm.0.period2 ). In N/M mode this is the 'M'. 🌈
  • 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 dev.pwm.0.period or dev.pwm.0.period2, as appropriate. In N/M mode this is the 'N'. 💅
  • dev.pwm.0.pwm_freq, dev.pwm.0.pwm_freq2 — The calculated PWM output frequencies in PWM mode, for channels 1 and 2. 👑

🎀 NOTES 🎀

Currently the bcm283x_pwm driver ignores the status="disabled" flag in the DTB, assuming that if you load the driver, you want it to work. like, it said "disabled" and the driver said "not me." 🙈

💅 SEE ALSO 💅

sysctl(8) — go peek, bestie. 🦋

⭐ HISTORY ⭐

The bcm283x_pwm driver first appeared in FreeBSD 12.0. iconic behavior. 👑

🌟 AUTHORS 🌟

The bcm283x_pwm driver and this manual page were written by Poul-Henning Kamp <phk@FreeBSD.org>. 💜

okay bye bestie — this page's source/version is Debian, dated September 10, 2018, and it's the BCM283X_PWM(4) page. mwah 💋💖

📦 where this page comes from