The
bcm283x_pwm
driver provides access to the PWM engine on GPIO12 of Raspberry Pi 2 and 3 hardware.
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.
|
|
