PWM

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Revision as of 18:20, 2 February 2007 by Salocin68 (Talk | contribs) (Usage)

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On this page, you will find usefull informations to configure and use the Pulse Width Modulation (PWM) capabilities of your APF9328 board.

Your is capable of driving 2 PWM signals:

  • one is linked to the LCD controller and allow to control LCD backlight, see LCD page for more informations
  • the other can be used to generate PWM signals in several mode:
* audio playback
* real PWM

Configuration

First be sure to have the PWM Linux driver activated:

$ make linux-menuconfig

File:PWMconfig.png

$ make

Installation

Either copy generated module target/linux/modules/pwm/pwm.ko to your system with TFTP or NFS or reflash the generated rootfs

Usage

Load the module:

# insmod /lib/modules/2.6.18.1/extra/pwm/pwm.ko

Now you have access to /sys/class/pwm/ functionnalities:

  • to activate PWM:
# echo 1 > /sys/class/pwm/pwm0/active
  • to de-activate PWM:
# echo 0 > /sys/class/pwm/pwm0/active
  • to change frequency (for example 500 Hz):
# echo 500 > /sys/class/pwm/pwm0/frequency
  • to change period (for example 100us):
# echo 100 > /sys/class/pwm/pwm0/period
  • to change duty cycle (for example 50.0%)
# echo 500 > /sys/class/pwm/pwm0/duty

Audio playback mode is not fully functionnal/tested yet. Ask JulienB if you really need it...

Links