PWM Access in Galileo Gen 2 in linux

[DRadi1]

Hi All,

I am using Intel Galileo Gen 2 board using linux and I want to access available 6 channels of PWM interface. I have configured the PWM in Gen2 baord as below script file.

# !/bin/bash

echo -n "out" > /sys/class/gpio/gpio26/direction

echo -n "1" > /sys/class/gpio/gpio26/value

echo -n "out" > /sys/class/gpio/gpio27/direction

echo -n "0" > /sys/class/gpio/gpio27/value

echo -n "1" > /sys/class/gpio/gpio74/value

echo -n "1" > /sys/class/pwm/pwmchip0/pwm11/enable

echo -n "3000000" > /sys/class/pwm/pwmchip0/device/pwm_period

echo -n "1500000" > /sys/class/pwm/pwmchip0/pwm11/duty_cycle

while true; do

echo "Start"

echo -n "out" > /sys/class/gpio/gpio26/direction

echo -n "1" > /sys/class/gpio/gpio26/value

echo -n "out" > /sys/class/gpio/gpio27/direction

echo -n "0" > /sys/class/gpio/gpio27/value

echo -n "1" > /sys/class/gpio/gpio74/value

echo "Complete"

sleep 1

done

But when i run the above script on gen 2 board and by observe in Oscilloscope i have notice some below results

Period Duty_cycle Time  

3000000 3000000 2.40ms  

3000000 1500000 1.20ms

3000000 750000 0.64ms

3000000 375000 0.32ms

So, According to the above table, i should get Time 3ms, 1.5ms, 0.75ms and 0.375ms instead of above time, but the difference is very large. what may be the reason and is this right output or not? Also when period is 6000000 and duty cycle is 6000000, then also i am getting time as 2.4ms. in this case my duty cycle is of 6ms so should i get 6ms on CRO or 2.4ms is correct?

Thank you.

[Sergio_A_Intel · Accepted solution]

Hi,

What image are you using? I made some tests and got different results. Correct me if I'm wrong but if you use a period of 3ms and a duty cycle of 100% then you should get a high pulse for the entire period, if you use 50% duty cycle you should get 1.5ms and so on.

I ran the code using 50%duty cycle and got 1.556ms. With 25% duty cycle I got 0.778ms. With 12.5% duty cycle I got 0.3737ms. So these values look pretty close to the theoric values. You can try with the code I'm using here https://github.com/MakersTeam/Galileo/blob/master/Arduino-Examples/setPWM_GalileoGen2.ino Galileo/setPWM_GalileoGen2.ino at master · MakersTeam/Galileo · GitHub

Sergio