Occidentalis Kernel Module for PWM

You can test if it loads with the insmod command.

You must be root to load kernel modules.

$ sudo su

$ insmod /path/to/module.ko

If it works you need to add it to your modules path so you can set up the configuration to load it each boot.

You can if you want just add a symbolic link to your module file to the modules directory:

$ sudo ln -s /path/to/module.ko /lib/modules/`uname -r`

$ sudo depmod -a

After that you can use the modprobe command:

$sudo modprobe module

Or add it to /etc/modules to auto load it at boot:

$ sudo su

$ echo module >> /etc/modules

$ reboot

You can test if your modules is loaded with the lsmod command:

$ lsmod

Module                  Size  Used by

tcp_lp                 12663  0

fuse                   86889  3

bnep                   19624  2

....

Hope this helps.

Hello Iago. I've checked with the lsmod command u said and it shows the pwm module in that list..but i have the following problem when i run the code for controlling a dc motor:

Error writing to: delayed value: 0

Error writing to: frequency value: 500

Error writing to: active value: 1

Command, f/r/o/p/s 0..9, E.g. f5 :

this is the code:

1. import RPi.GPIO as io
2. io.setmode(io.BCM)
4. in1_pin = 4
5. in2_pin = 17
7. io.setup(in1_pin, io.OUT)
8. io.setup(in2_pin, io.OUT)
10. def set(property, value):
11.    try:
12.   f = open("/sys/class/rpi-pwm/pwm0/" + property, 'w')
13.   f.write(value)
14.   f.close()
15.    except:
16.    print("Error writing to: " + property + " value: " + value)
18. set("delayed", "0")
19. set("mode", "pwm")
20. set("frequency", "500")
21. set("active", "1")
23. def clockwise():
24.   io.output(in1_pin, True)  
25.   io.output(in2_pin, False)
27. def counter_clockwise():
28.   io.output(in1_pin, False)
29.   io.output(in2_pin, True)
31. clockwise()
33. while True:
34.   cmd = raw_input("Command, f/r 0..9, E.g. f5 :")
35.   direction = cmd[0]
36.    if direction == "f":
37.   clockwise()
38.    else:
39.   counter_clockwise()
40.   speed = int(cmd[1]) * 11
41.    set("duty", str(speed))

i think here may be the problem : "/sys/class/rpi-pwm/pwm0/" ... it doesn't know that path....i'm runnig Raspbian not Occidentalis...

Can you help pls?

can you write here the output of this command ?

sudo ls -al /sys/class/rpi-pwm/pwm0/

Hey Iago,

I managed to do the PWM but i've hit another issue...i wanted to control a servomotor and i've pluged it like here:http://learn.adafruit.com/assets/3498 using a 12V power supply...and my Pi just shut down...and now it doesn't boot...my red led stays on and at first the act blinked a little but now nothing...only the red led stays on and i have no output on the monitor...i may have burned it? it was the same power supply used for the dc motor which worked perfectly...

The servo motor is a completely different beast.

The PWM on the DC motor is used just to limit the voltage on it. So a 50% duty cycle get half the voltage on the motor than a 100% duty cycle.

The PWM on the servo motor, must be a fixed frequency 20ms PWM signal and the high duration on the PWM signal gives the servo the angle it must stay. So if in that 20ms PWM signal the high state is 0.5ms it stays at -90º and if it's 2.5ms it stays at +90º.

Never use a DC motor controller to control servos.

In the other hand 12V seems to be a quite high voltage for a RC servo. They use to go with 6V.

So if the servo was low quality and the 12V voltage "fried" it and it poured into to the the Raspberry's signal wire , there is a high chance of it being dead. The GPIOs on the raspberry are 3.3V tolerant and 12V in there is far too much.

The 12V may be normal for a DC motor as they are more resilient, but the flyback - the EMC voltage when the electric field on the motor coil collapses - can also kill the raspberry, and you may use any kind of IC with built in flyback diodes or some kind of protection.

So what to check:

Is the Servo motor 12V tolerant ?

Is it ok and alive ?

If you don't know if it's 12V tolerant just link it here.

But I am afraid there is a middle to high chance of that Raspberry being dead.

this is the servo http://www.es.co.th/schemetic/pdf/et-servo-s3003.pdf

i don't think the servo is dead though...

or why does the PWR led still stays on and the ACT for reading the SD card sometimes flashes?

The power led D6  will be on if the board is powered.

If the ACT led D5 flashes in a pattern it may mean there is a known error:

• 3 flashes: start.elf not found
• 4 flashes: start.elf not launched
• 7 flashes: kernel.img not found
• 8 flashes: SDRAM not recognised.

http://elinux.org/R-Pi_Troubleshooting#Green_LED_blinks_in_a_specific_pattern

The servo is 4.8V to 6V, you should not connect it to 12V.

I would try first to boot it with a new SD card and see if that changes anything.

the ACT led doesn't blink anymore.

I have 2 SD's but it doesn't change anything.

I've tested the voltage between the TP1 and TP2 points with a multimeter and i got a 3V value and between TP2 and polyfuse a 2.7V on a side and a 3.2V on the other...i've read that the polyfuse is self repairing over a few days...problem is i'm on a timetable and i don't know what to do...buy a new one or wait..what do you think?