gpio-pwm-ar9331

PWM generator using AR9331 hardware timer.

gpio-pwm-ar9331 is an OpenWRT kernel module which provides PWM output on any AR9331 SoC GPIO pin with up to 125 kHz frequency.

##Intallation

1. Build it using OpenWRT Buildroot.
2. Upload package to device using your favorite method.
3. Run opkg install kmod-gpio-pwm-ar9331_<version>.ipk where <version> is version of a package.

##Building

1. Clone this repository to buildrootdir/package (i.e. cd /path/to/buildroot/ then cd package/ and git clone https://github.com/ASMfreaK/gpio-pwm-ar9331.git)
2. Run make menuconfig and select Kernel modules ---> then Other modules ---> and finally kmod-gpio-pwm-ar9331. Select other packages if needed and exit the dialog.
3. Run make
4. Install the freshly built firmware to BlackSwift.

##Initialisation insmod gpio-pwm-ar9331
Default is timer 3

##Usage

Start: echo "+ <timer> <GPIO> <freq> <pos>" > /sys/kernel/debug/pwm-ar9331
timer is timer number (one of 0, 1, 2, 3), GPIO is GPIO number, freq is square wave frequency in Hz, pos is a number between 0 and 65536 representing duty cycle. At different frequencies it can generate up to 16 bit PWM Maximum frequency with 200 MHz system bus (default clock) is 125 kHz; high settings may result in performance penalty or watchdog reset.

Example: to blink Black Swift's system LED with 1 Hz frequency at around 1/2 duty cycle using timer 0: echo "+ 0 27 1 3000" > /sys/kernel/debug/pwm-ar9331

Stop: echo - > /sys/kernel/debug/pwm-ar9331

Status: echo ? > /sys/kernel/debug/pwm-ar9331