Pin Muxing

When working with the ports on the Linux-level, Pin Muxing are performed by MRAA library. In the case of the microcontroller it is necessary to take care with scripts...

MRAA Low Level Skeleton Library for IO Communication on GNU/Linux platforms

Configuring all 4 of the PWM pins

    root@edison:~# vi pinmuxpwm.sh

    #!/bin/bash

    # Configuring PWM pins
    # The Intel Edison SoC offers only four PWM pins.

    # Setup shield pins of arduino as a PWM output

    # the TRI_STATE_ALL signal is controlled by GPIO 214
    # Before setting up any muxing, set pin 214 (TRI_STATE_ALL) to HIGH, 
    # make all of your changes, then set pin 214 to LOW.

    # all GPIO pin-mux must be set to 'mode1' to select PWM

    # Shield_Pin  |  Linux_GPIO | Output=High | Pullup_enable
    #       IO3         12          251             219
    #       IO5         13          253             221
    #       IO6         182         254             222
    #       IO9         183         257             225

    #Export the relevant pins
    echo 251 > /sys/class/gpio/export
    echo 219 > /sys/class/gpio/export
    echo 253 > /sys/class/gpio/export
    echo 221 > /sys/class/gpio/export
    echo 254 > /sys/class/gpio/export
    echo 222 > /sys/class/gpio/export
    echo 257 > /sys/class/gpio/export
    echo 225 > /sys/class/gpio/export
    echo 214 > /sys/class/gpio/export

    echo "Exports Done"

    # FIRST Shield_pinIO3
    echo low > /sys/class/gpio/gpio214/direction
    echo high > /sys/class/gpio/gpio251/direction
    echo in > /sys/class/gpio/gpio219/direction
    echo mode1 > /sys/kernel/debug/gpio_debug/gpio12/current_pinmux
    echo high > /sys/class/gpio/gpio214/direction

    # SECOND Shield_pinIO5
    echo low > /sys/class/gpio/gpio214/direction
    echo high > /sys/class/gpio/gpio253/direction
    echo in > /sys/class/gpio/gpio221/direction
    echo mode1 > /sys/kernel/debug/gpio_debug/gpio13/current_pinmux
    echo high > /sys/class/gpio/gpio214/direction

    # THIRD Shield_pinIO6
    echo low > /sys/class/gpio/gpio214/direction
    echo high > /sys/class/gpio/gpio254/direction
    echo in > /sys/class/gpio/gpio222/direction
    echo mode1 > /sys/kernel/debug/gpio_debug/gpio182/current_pinmux
    echo high > /sys/class/gpio/gpio214/direction

    # FOURTH Shield_pinIO9
    echo low > /sys/class/gpio/gpio214/direction
    echo high > /sys/class/gpio/gpio257/direction
    echo in > /sys/class/gpio/gpio225/direction
    echo mode1 > /sys/kernel/debug/gpio_debug/gpio183/current_pinmux
    echo high > /sys/class/gpio/gpio214/direction

    echo "PWM Pins Configured"

You should be able to use any of the PWM pins as output. For example pin IO6:

    root@edison:~# echo 2 > /sys/class/pwm/pwmchip0/export
    root@edison:~# echo 2000000 > /sys/class/pwm/pwmchip0/pwm2/duty_cycle
    root@edison:~# echo 1 > /sys/class/pwm/pwmchip0/pwm2/enable