Problems with my BeagleBone Black PWM.

[tomek242]

Hello everyone.
I have a big problem with my BBB. I try to use my board to simple tracking robot with DAGU Rover 5 chassis and DAGU motor driver board but... whatever version of debian i try to use, I see the same errors:
RuntimeError: You must start() the PWM channel first; or
ehrpwm error - duty is larger than period; or
RuntimeError: Problem with /sysfs.
Of course i try to use THIS solutions but there is no results still that same errors. I checked that problems for Angstrom, Debian 7,2; 7,11; 8.5; 8.7; 9.1 with beaglebone-universal-io and without it, but still no effect.
Maybe someone here had working Debian uSD image with properly configured cape, or help some in configuration this?
Greetings. Thanks.

[silver2row]

Hello tomek242,

My name is Seth. I just published a concern with similar instances of PWM not working. I get the RuntimeError: Problem with sysfs, too.

I tried a handful of resources and asked around. I could not get the PWM to start in working order for my software.

My software is from #168. I get the sysfs entry error and I have tried bone_capemgr, overlays, and config-pin pwm for writing the software while in the current terminal. I have empty answers so far.

tomek242: If you figure something out, please let me know. I would love to get my book software to work.

Seth

P.S. Thank you for posting about this issue.

[tomek242]

Hello Seth.

Unfortunately, until now I have not been able to solve these problems. That's why I wrote about my issue here. Perhaps one of the developers has done it and is working properly.
Greetings.

[pdp7]

@tomek242 sorry for my delayed response.

I'd like to get some information about what is currently running on your BeagleBone. Please paste the output of the following commands:

cat /etc/dogtag 
cat /etc/debian_version 
cat /proc/cmdline 
cat /sys/devices/platform/bone_capemgr/slots
cat /boot/uEnv.txt 
config-pin -q p9.14
uname -a

FYI: Adafruit_BBIO (this library) no longer supports the Angstrom images. The official BeagleBoard.org image has been Debian-based since 2014. For more info: BeagleBoard.org Latest Images

I'd also like you to try this test. Start the Python interpreter:

sudo python

Then type or paste these lines:

import Adafruit_BBIO.PWM as PWM
#PWM.start(channel, duty, freq=2000, polarity=0)
#duty values are valid 0 (off) to 100 (on)
PWM.start("P9_14", 50)
PWM.set_duty_cycle("P9_14", 25.5)
PWM.set_frequency("P9_14", 10)

PWM.stop("P9_14")
PWM.cleanup()

#set polarity to 1 on start:
PWM.start("P9_14", 50, 2000, 1)

Please paste the output including any errors messages here.

If no error occurs, then the results should be similar to:

debian@beaglebone:~$ sudo python
[sudo] password for debian: 
Python 2.7.9 (default, Aug 13 2016, 17:56:53) 
[GCC 4.9.2] on linux2
Type "help", "copyright", "credits" or "license" for more information.
>>> 
>>> import Adafruit_BBIO.PWM as PWM
>>> #PWM.start(channel, duty, freq=2000, polarity=0)
... #duty values are valid 0 (off) to 100 (on)
... PWM.start("P9_14", 50)
>>> PWM.set_duty_cycle("P9_14", 25.5)
>>> PWM.set_frequency("P9_14", 10)
>>> 
>>> PWM.stop("P9_14")
>>> PWM.cleanup()
>>> 
>>> #set polarity to 1 on start:
... PWM.start("P9_14", 50, 2000, 1)
>>> exit
Use exit() or Ctrl-D (i.e. EOF) to exit
>>> exit()

In addition, I'd also like to know which pins on the BeagleBone that you are using for your project.

Would it be possible for you to post a link to a photo of your project?

( @silver2row I've just replied in #168 )

[pdp7]

@tomek242 I just posted about this to @silver2row in #168. I believe there is problem with using PWM with the Linux 4.9 kernel and Adafruit_BBIO. I need to investigate and resolve that issue.

In the meantime, please ensure that you are running the Linux 4.4 kernel.

Please try installing the Linux 4.4 kernel with these instructions:

cd /opt/scripts/tools/
sudo git pull
sudo ./update_kernel.sh --lts-4_4
sudo reboot

The above presumes that you are using an official BeagleBoard.org Debian image

[tomek242]

Hello Drew.
I've just worked with Debian 8.3 with 4.1.15-ti-rt-r43 #1 SMP PREEMPT RT Thu Jan 21 20:13:58 UTC 2016 armv7l GNU/Linux
taken from one of Your posts - I think:) (https://gist.github.com/pdp7/aad85478890f37ac7a19538e9702f69c)

At this time, that the only image when my test program realy work. For example when i typing:

root@beaglebone:~# cat /sys/devices/platform/bone_capemgr/slots

I take this:

 0: PF----  -1 
 1: PF----  -1 
 2: PF----  -1 
 3: PF----  -1 
 4: P-O-L-   0 Override Board Name,00A0,Override Manuf,cape-universaln

Besides:
root@beaglebone:~# cat /etc/dogtag
BeagleBoard.org Debian Image 2016-01-24
Debian ver. is 8.3 (as i wrote - the only worked image) - personally it could be better for me using 7.11 or 9.1.

root@beaglebone:~# cat /proc/cmdline
console=tty0 console=ttyO0,115200n8 root=/dev/mmcblk0p1 rootfstype=ext4 rootwait coherent_pool=1M quiet cape_universal=enable

And another think, as I said:

root@beaglebone:~# cat /sys/devices/platform/bone_capemgr/slots
 0: PF----  -1
 1: PF----  -1
 2: PF----  -1
 3: PF----  -1
 4: P-O-L-   0 Override Board Name,00A0,Override Manuf,cape-universal

root@beaglebone:~# cat /boot/uEnv.txt
#Docs: http://elinux.org/Beagleboard:U-boot_partitioning_layout_2.0
uname_r=4.1.15-ti-rt-r43
#uuid=
#dtb=
##BeagleBone Black/Green dtb's for v4.1.x (BeagleBone White just works..)
##BeagleBone Black: HDMI (Audio/Video) disabled:
#dtb=am335x-boneblack-emmc-overlay.dtb
##BeagleBone Black: eMMC disabled:
#dtb=am335x-boneblack-hdmi-overlay.dtb
##BeagleBone Black: HDMI Audio/eMMC disabled:
#dtb=am335x-boneblack-nhdmi-overlay.dtb
##BeagleBone Black: HDMI (Audio/Video)/eMMC disabled:
#dtb=am335x-boneblack-overlay.dtb
##BeagleBone Black: wl1835
#dtb=am335x-boneblack-wl1835mod.dtb
##BeagleBone Green: eMMC disabled
#dtb=am335x-bonegreen-overlay.dtb
cmdline=coherent_pool=1M quiet cape_universal=enable
#In the event of edid real failures, uncomment this next line:
#cmdline=coherent_pool=1M quiet cape_universal=enable video=HDMI-A-1:1024x768@60e
##Example v3.8.x
#cape_disable=capemgr.disable_partno=
#cape_enable=capemgr.enable_partno=
##Example v4.1.x
#cape_disable=bone_capemgr.disable_partno=
#cape_enable=bone_capemgr.enable_partno=
##Disable HDMI/eMMC (v3.8.x)
#cape_disable=capemgr.disable_partno=BB-BONELT-HDMI,BB-BONELT-HDMIN,BB-BONE-EMMC-2G
##Disable HDMI (v3.8.x)
#cape_disable=capemgr.disable_partno=BB-BONELT-HDMI,BB-BONELT-HDMIN
##Disable eMMC (v3.8.x)
#cape_disable=capemgr.disable_partno=BB-BONE-EMMC-2G
##Audio Cape (needs HDMI Audio disabled) (v3.8.x)
#cape_disable=capemgr.disable_partno=BB-BONELT-HDMI
#cape_enable=capemgr.enable_partno=BB-BONE-AUDI-02
##enable Generic eMMC Flasher:
##make sure, these tools are installed: dosfstools rsync
#cmdline=init=/opt/scripts/tools/eMMC/init-eMMC-flasher-v3.sh

Another suggested command:

root@beaglebone:~# config-pin -q p9.14
                                       P9_14 Mode: pwm

PYthon test:

root@beaglebone:~# sudo python
Python 2.7.9 (default, Mar  1 2015, 13:48:22)
[GCC 4.9.2] on linux2
Type "help", "copyright", "credits" or "license" for more information.

And test in python code:

root@beaglebone:~# sudo python
Python 2.7.9 (default, Mar  1 2015, 13:48:22)
[GCC 4.9.2] on linux2
Type "help", "copyright", "credits" or "license" for more information.
>>> import Adafruit_BBIO.PWM as PWM
>>> #PWM.start(channel, duty, freq=2000, polarity=0)
... #duty values are valid 0 (off) to 100 (on)
... PWM.start("P9_14", 50)
>>> PWM.set_duty_cycle("P9_14", 25.5)
>>> PWM.set_frequency("P9_14", 10)
Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
RuntimeError: Could not write to the frequency file
>>>
>>> PWM.stop("P9_14")
>>> PWM.cleanup()
>>>
>>> #set polarity to 1 on start:
... PWM.start("P9_14", 50, 2000, 1)

I try some other kernels for example that what You recomended for me, I mean:

sudo ./update_kernel.sh --lts-4_4
But any result.
I've been suffering with this for month. Unfortunately without any result.
In my case i planned to use four pairs of pins:

EHRPWM1A P9_14 and GPIO_117 P9_25 -> for encoder
EHRPWM1B P9_16 and GPIO_115 P9_27 -> for encoder
EHRPWM2A P8_19 and GPIO_47 P8_15 -> for encoder
EHRPWM2B P8_13 and GPIO_27 P8_17 -> for encoder

I planning to use in my project this GPIO's to "listen" (i don't know how it's write in English) signal from encoders and PWM pins to drive four motors in DAGU Rover 5 tracked chassis with motor driver board taken from Dagu also (I show it at this link)

In case when I use Debian 9.1 i seems they dont load cape-universaln and in case when i try Debian 7.11 i saw this:
ehrpwm error: Duty is larger than Period - or something like that.

I think thats all at now, and of course sorry, if I wrote something wrong but i don't speak well in English.
Thanks for Your interest Drew

[tomek242]

Ok. I was install 4.4 lts kernel and this is result:

Code:

import Adafruit_BBIO.PWM as PWM
myPWM="P9_16"
PWM.start(myPWM, 0, 1000)
for i in range(0,5):
DC=input("What Duty Cycle Would You Like (0-100)? ")
PWM.set_duty_cycle(myPWM, DC)
PWM.stop(myPWM)
PWM.cleanup()

Takes effect:

python test2.py
[  183.195393] ehrpwm 48302200.pwm: Period value conflicts with channel 0
Traceback (most recent call last):
  File "test2.py", line 5, in <module>
    PWM.start(myPWM, 0, 1000)
RuntimeError: Problem with a sysfs file

And
in this case of code:

#!/usr/bin/python
import Adafruit_BBIO.PWM as PWM
import time
pin1 = "P9_14"
pin2 = "P9_16"
pin3 = "P8_19"
pin4 = "P8_13"
PWM.start(pin1,0)
PWM.start(pin2,0)
PWM.start(pin3,0)
PWM.start(pin4,0)
for i in range(0,100):  #loop 100 times
        PWM.set_duty_cycle(pin1,100)
        PWM.set_duty_cycle(pin2,100)
        PWM.set_duty_cycle(pin3,100)
        PWM.set_duty_cycle(pin4,100)
time.sleep(1)
PWM.stop(pin1)
PWM.stop(pin2)
PWM.stop(pin3)
PWM.stop(pin4)
PWM.cleanup()

Everything seems work good :(

Uhhhh a just think that will be so easy:)

[tomek242]

Any suggestions folks? :)

[silver2row]

Hello,

If I use the resistor to limit current, there is still current going through it at another spot on the breadboard. If I was to add additional requirements, normally open window sensor and other resistors, I could come across an issue with supply.

Power may become an issue.

Seth

P.S. I may need more voltage, i.e. 5v or higher with the correct digital equipment.

[silver2row]

We may be seeing issues with power on our boards when attempting to write the software and have it produce the correct results.

Seth

[silver2row]

Hello Again,

The Motor Driver probably needs to be powered separately from you BBB.

Seth

[tomek242]

Hello Seth.

I think it does not matter beacause logic level cames from BBB to driver has maybe (cirka) 3,3V not more so I think thats not a problem.
Personally i powered my board and BBB separately each from another source (two DC - DC converters with power distribution boards one for 12V, for motors and the second for 5V for board logic).
However The BBB use 5V logic (As I think remember). So if You are not sure about the logic states values take a look this:
http://slideplayer.pl/slide/3624618/11/images/3/Poziomy+napięć+w+standardowym+układzie+TTL.jpg
or this http://ep.com.pl/cache/images/norm/3/0/6/c3JjPS9pbWFnZXMvbm9ybS8zLzAvNi8xNzMwNmtvbndlcnRlcnlfMS5qcGcmdz04ODgmaD03MzA=_srcc00682232e2d35c16ff54a61de9aa8df.jpg

I think the real problem is software, I mean Debian and pins configurtion. not pin voltages :)
Tom