Re: [beagleboard] Re: how to make pwm_P8_13 low on boot?

[janszymanski12345]

Hi Jon,
Thanks, that works and behaves exactly as I need.
Jan

On Friday, 5 December 2014 10:54:39 UTC+11, Jon E wrote:
>
> I used roughly the following process; 
>
> 1) grab the original source file & copy to a local version 
>
> wget 
>
> https://raw.githubusercontent.com/beagleboard/linux/3.8.13-bone66/firmware/capes/bone_pwm_P8_13-00A0.dts
>  
>
> cp bone_pwm_P8_13-00A0.dts bone_pwm_local-00A0.dts 
>
> 2) change the part-number in your local version of the .dts file 
>
> < part-number = "bone_pwm_P8_13"; 
> --- 
>  > part-number = "bone_pwm_local_P8_13"; 
>
> 3) compile & copy to /lib/firmware 
>
> dtc -O dtb -o bone_pwm_local-00A0.dtbo -b 0 -@ bone_pwm_local-00A0.dts 
>
> cp bone_pwm_local-00A0.dtbo /lib/firmware/ 
>
> 4) load the am33xx_pwm overlay, plus your local config for your pin 
>
> echo am33xx_pwm  >/sys/devices/bone_capemgr.*/slots 
> echo bone_pwm_local >/sys/devices/bone_capemgr.*/slots 
>
> Those steps should be enough; 
>
> root@beaglebone:~# ls /sys/devices/ocp.*/pwm_test_P8_13.*/ 
> driverduty  modaliasperiodpolarity  power  run 
>  subsystem  uevent 
>
> Regards, 
> Jon 
>
>
> On 04/12/14 23:21, janszyma...@gmail.com  wrote: 
> > OK, I did the renaming from "bone_pwm_P8_13-00A0.* " into 
> > "bone_pwm_test-00A0.*" and after reboot I have: 
> > 
> > in slots: 
> >   0: 54:PF--- 
> >   1: 55:PF--- 
> >   2: 56:PF--- 
> >   3: 57:PF--- 
> >   4: ff:P-O-L Bone-LT-eMMC-2G,00A0,Texas Instrument,BB-BONE-EMMC-2G 
> >   5: ff:P-O-L Bone-Black-HDMI,00A0,Texas Instrument,BB-BONELT-HDMI 
> >   7: ff:P-O-L Override Board Name,00A0,Override Manuf,BB-UART1 
> >   8: ff:P-O-L Override Board Name,00A0,Override Manuf,SPI-4SS 
> >   9: ff:P-O-L Override Board Name,00A0,Override Manuf,bone_eqep2b 
> > 10: ff:P-O-L Override Board Name,00A0,Override Manuf,bone_pwm_test 
> > 11: ff:P-O-L Override Board Name,00A0,Override Manuf,am33xx_pwm 
> > 
> > but in  /sys/devices/ocp.3/pwm_test_P8_13.16 I have only: 
> > 
> > root@beaglebone:/sys/devices/ocp.3/pwm_test_P8_13.16# ls 
> > modalias  power  subsystem  uevent 
> > 
> > My bone_pwm_test-00A0.dts and bone_pwm_test-00A0.dtb0 are in 
> /lib/firmware 
> > Do I need to make any changes to them after all (as the renaming only 
> > doesn't work)? 
> > 
> > Jan 
>
>

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Re: [beagleboard] Re: how to make pwm_P8_13 low on boot?

[Jon Escombe]

I used roughly the following process;

1) grab the original source file & copy to a local version

wget 
https://raw.githubusercontent.com/beagleboard/linux/3.8.13-bone66/firmware/capes/bone_pwm_P8_13-00A0.dts


cp bone_pwm_P8_13-00A0.dts bone_pwm_local-00A0.dts

2) change the part-number in your local version of the .dts file

part-number = "bone_pwm_local_P8_13";

3) compile & copy to /lib/firmware

dtc -O dtb -o bone_pwm_local-00A0.dtbo -b 0 -@ bone_pwm_local-00A0.dts

cp bone_pwm_local-00A0.dtbo /lib/firmware/

4) load the am33xx_pwm overlay, plus your local config for your pin

echo am33xx_pwm  >/sys/devices/bone_capemgr.*/slots
echo bone_pwm_local >/sys/devices/bone_capemgr.*/slots

Those steps should be enough;

root@beaglebone:~# ls /sys/devices/ocp.*/pwm_test_P8_13.*/
driver  duty  modalias  period  polarity  power  run  subsystem  uevent

Regards,
Jon


On 04/12/14 23:21, janszymanski12...@gmail.com wrote:

OK, I did the renaming from "bone_pwm_P8_13-00A0.* " into
"bone_pwm_test-00A0.*" and after reboot I have:

in slots:
  0: 54:PF---
  1: 55:PF---
  2: 56:PF---
  3: 57:PF---
  4: ff:P-O-L Bone-LT-eMMC-2G,00A0,Texas Instrument,BB-BONE-EMMC-2G
  5: ff:P-O-L Bone-Black-HDMI,00A0,Texas Instrument,BB-BONELT-HDMI
  7: ff:P-O-L Override Board Name,00A0,Override Manuf,BB-UART1
  8: ff:P-O-L Override Board Name,00A0,Override Manuf,SPI-4SS
  9: ff:P-O-L Override Board Name,00A0,Override Manuf,bone_eqep2b
10: ff:P-O-L Override Board Name,00A0,Override Manuf,bone_pwm_test
11: ff:P-O-L Override Board Name,00A0,Override Manuf,am33xx_pwm

but in  /sys/devices/ocp.3/pwm_test_P8_13.16 I have only:

root@beaglebone:/sys/devices/ocp.3/pwm_test_P8_13.16# ls
modalias  power  subsystem  uevent

My bone_pwm_test-00A0.dts and bone_pwm_test-00A0.dtb0 are in /lib/firmware
Do I need to make any changes to them after all (as the renaming only
doesn't work)?

Jan


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Re: [beagleboard] Re: how to make pwm_P8_13 low on boot?

[janszymanski12345]

OK, I did the renaming from "bone_pwm_P8_13-00A0.* " into 
"bone_pwm_test-00A0.*" and after reboot I have: 

in slots:
 0: 54:PF--- 
 1: 55:PF--- 
 2: 56:PF--- 
 3: 57:PF--- 
 4: ff:P-O-L Bone-LT-eMMC-2G,00A0,Texas Instrument,BB-BONE-EMMC-2G
 5: ff:P-O-L Bone-Black-HDMI,00A0,Texas Instrument,BB-BONELT-HDMI
 7: ff:P-O-L Override Board Name,00A0,Override Manuf,BB-UART1
 8: ff:P-O-L Override Board Name,00A0,Override Manuf,SPI-4SS
 9: ff:P-O-L Override Board Name,00A0,Override Manuf,bone_eqep2b
10: ff:P-O-L Override Board Name,00A0,Override Manuf,bone_pwm_test
11: ff:P-O-L Override Board Name,00A0,Override Manuf,am33xx_pwm

but in  /sys/devices/ocp.3/pwm_test_P8_13.16 I have only:

root@beaglebone:/sys/devices/ocp.3/pwm_test_P8_13.16# ls
modalias  power  subsystem  uevent

My bone_pwm_test-00A0.dts and bone_pwm_test-00A0.dtb0 are in /lib/firmware
Do I need to make any changes to them after all (as the renaming only 
doesn't work)?

Jan




On Friday, 5 December 2014 09:10:53 UTC+11, RobertCNelson wrote:
>
> On Thu, Dec 4, 2014 at 4:09 PM,  > 
> wrote: 
> > Thanks Robert, 
> > 
> > Is there a way to overwrite it? 
>
> Rename your local version.. 
>
> > How can I tell which ones are builtin (so I can select another PWM 
> module 
> > and pin)? 
>
> You can see them here: 
>
> https://github.com/beagleboard/linux/tree/3.8/firmware/capes 
>
> Regards, 
>
> -- 
> Robert Nelson 
> http://www.rcn-ee.com/ 
>

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Re: [beagleboard] Re: how to make pwm_P8_13 low on boot?

[Robert Nelson]

On Thu, Dec 4, 2014 at 4:09 PM,   wrote:
> Thanks Robert,
>
> Is there a way to overwrite it?

Rename your local version..

> How can I tell which ones are builtin (so I can select another PWM module
> and pin)?

You can see them here:

https://github.com/beagleboard/linux/tree/3.8/firmware/capes

Regards,

-- 
Robert Nelson
http://www.rcn-ee.com/

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Re: [beagleboard] Re: how to make pwm_P8_13 low on boot?

[janszymanski12345]

Thanks Robert,

Is there a way to overwrite it?
How can I tell which ones are builtin (so I can select another PWM module 
and pin)?

Jan

On Friday, December 5, 2014 8:39:00 AM UTC+11, RobertCNelson wrote:
>
> On Thu, Dec 4, 2014 at 3:37 PM,  > 
> wrote: 
> > Jon, 
> > 
> >  Thank you for your valuable input. 
> > I will try it soon and let you know. 
> > The obvious question already is which one will take precedence in 
> loading: 
> > the overlay defined in the kernel or the one handled by the cape 
> manager? 
>
> The one built-in.. 
>
> Regards, 
>
> -- 
> Robert Nelson 
> http://www.rcn-ee.com/ 
>

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Re: [beagleboard] Re: how to make pwm_P8_13 low on boot?

[Robert Nelson]

On Thu, Dec 4, 2014 at 3:37 PM,   wrote:
> Jon,
>
>  Thank you for your valuable input.
> I will try it soon and let you know.
> The obvious question already is which one will take precedence in loading:
> the overlay defined in the kernel or the one handled by the cape manager?

The one built-in..

Regards,

-- 
Robert Nelson
http://www.rcn-ee.com/

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Re: [beagleboard] Re: how to make pwm_P8_13 low on boot?

[janszymanski12345]

Jon,

 Thank you for your valuable input.
I will try it soon and let you know.
The obvious question already is which one will take precedence in loading:
the overlay defined in the kernel or the one handled by the cape manager?

Cheers,

Jan

On Friday, December 5, 2014 5:34:44 AM UTC+11, Jon E wrote:
>
> Hi Jan, 
>
> I had another look at this, was able to replicate what you are seeing, 
> and think I know what's going on.. 
>
> The part-number 'bone_pwm_P8_13' is already included in the kernel 
> build. I'm not really sure of the mechanics, but when doing a build from 
> the git repository, all the .dts files in the /firmware/capes folder get 
> compiled to individual .dtbo files, and from there into object files, 
> and then combined into a single built-in.o file. 
>
> The end result of this appears to be that putting an overlay file for 
> one of these built-in part-numbers into /lib/firmware doesn't achieve 
> anything, it just doesn't get read (even if you increment the version). 
>
> Anyway, it's an easy fix - once you know what's going on!! You should 
> just need to change the part-number to something else unique (and the 
> file name to suit), and then the options can be set in your overlay as 
> you'd expect.. 
>
> Hope this helps, 
> Jon. 
>
>
> On 26/11/14 10:11, janszyma...@gmail.com  wrote: 
> > Good idea, thanks. I will try it. I think the positive pulse will be so 
> > short that it will not be able to move the motor. 
> > 
> > On Wednesday, November 26, 2014 8:29:31 PM UTC+11, Jon E wrote: 
> > 
> > I'm not sure about that. Jan said before that it's only driven high 
> > after loading the PWM driver, and the processor datasheet shows ball 
> > T10 (P8_13) as driven low during/after reset. 
> > 
> > Jan, not ideal, but to disable the output sooner you could load the 
> > overlay through cape manager, and then write 0 to the run parameter 
> > immedately afterwards. But I still think the correct approach is to 
> > look at the devcetree/driver code and see why those parameters are 
> > having no affect.. 
> > 
> > Regards, 
> > Jon 
>
>

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Re: [beagleboard] Re: how to make pwm_P8_13 low on boot?

[Jon Escombe]

Hi Jan,

I had another look at this, was able to replicate what you are seeing, 
and think I know what's going on..


The part-number 'bone_pwm_P8_13' is already included in the kernel 
build. I'm not really sure of the mechanics, but when doing a build from 
the git repository, all the .dts files in the /firmware/capes folder get 
compiled to individual .dtbo files, and from there into object files, 
and then combined into a single built-in.o file.


The end result of this appears to be that putting an overlay file for 
one of these built-in part-numbers into /lib/firmware doesn't achieve 
anything, it just doesn't get read (even if you increment the version).


Anyway, it's an easy fix - once you know what's going on!! You should 
just need to change the part-number to something else unique (and the 
file name to suit), and then the options can be set in your overlay as 
you'd expect..


Hope this helps,
Jon.


On 26/11/14 10:11, janszymanski12...@gmail.com wrote:

Good idea, thanks. I will try it. I think the positive pulse will be so
short that it will not be able to move the motor.

On Wednesday, November 26, 2014 8:29:31 PM UTC+11, Jon E wrote:

I'm not sure about that. Jan said before that it's only driven high
after loading the PWM driver, and the processor datasheet shows ball
T10 (P8_13) as driven low during/after reset.

Jan, not ideal, but to disable the output sooner you could load the
overlay through cape manager, and then write 0 to the run parameter
immedately afterwards. But I still think the correct approach is to
look at the devcetree/driver code and see why those parameters are
having no affect..

Regards,
Jon


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Re: [beagleboard] Re: how to make pwm_P8_13 low on boot?

[janszymanski12345]

Good idea, thanks. I will try it. I think the positive pulse will be so 
short that it will not be able to move the motor.

On Wednesday, November 26, 2014 8:29:31 PM UTC+11, Jon E wrote:
>
> I'm not sure about that. Jan said before that it's only driven high after 
> loading the PWM driver, and the processor datasheet shows ball T10 
> (P8_13) as driven low during/after reset. 
>
> Jan, not ideal, but to disable the output sooner you could load the 
> overlay through cape manager, and then write 0 to the run parameter 
> immedately afterwards. But I still think the correct approach is to look 
> at the devcetree/driver code and see why those parameters are having no 
> affect..
>
> Regards,
> Jon
>
> On Wednesday, 26 November 2014 03:43:21 UTC, William Hermans wrote:
>>
>> IN short, use external hardware or do something cleaver like Peter G, and 
>> reverse polarity. *OR* have an external "switch" that switches the PWM line 
>> off, until you tell it to turn on. simples ?
>>
>

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Re: [beagleboard] Re: how to make pwm_P8_13 low on boot?

[Jon E]

I'm not sure about that. Jan said before that it's only driven high after 
loading the PWM driver, and the processor datasheet shows ball T10 (P8_13) 
as driven low during/after reset. 

Jan, not ideal, but to disable the output sooner you could load the overlay 
through cape manager, and then write 0 to the run parameter immedately 
afterwards. But I still think the correct approach is to look at the 
devcetree/driver code and see why those parameters are having no affect..

Regards,
Jon

On Wednesday, 26 November 2014 03:43:21 UTC, William Hermans wrote:
>
> IN short, use external hardware or do something cleaver like Peter G, and 
> reverse polarity. *OR* have an external "switch" that switches the PWM line 
> off, until you tell it to turn on. simples ?
>

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Re: [beagleboard] Re: how to make pwm_P8_13 low on boot?

[William Hermans]

IN short, use external hardware or do something cleaver like Peter G, and
reverse polarity. *OR* have an external "switch" that switches the PWM line
off, until you tell it to turn on. simples ?

On Tue, Nov 25, 2014 at 7:26 PM, Miguel Aveiro <
miguel.ave...@brascontrol.com.br> wrote:

>  It's not a kernel driver, I believe it's the processor default mode. You
> can check the processor datasheet:
>
> http://www.ti.com/product/AM3359/datasheet/terminal_description?search=pin,default#sprs717824
>
> If you want to change it earlier than linux, you need to set the pin in
> uboot (as far as I can understand). You can check the list because I know
> that I have already read something about change default IO in BBB. Or
> something about u-boot and gpio, like this:
> http://www.crashcourse.ca/wiki/index.php/U-Boot_on_the_BBB
>
> Hopefully, this can help a little
>
> Miguel Aveiro
>
> On 25-11-2014 22:28, janszymanski12...@gmail.com wrote:
>
> thanks, unfortunately didn't work for me.
>
> On Wednesday, 26 November 2014 10:02:27 UTC+11, Peter Gregory wrote:
>>
>> I had the same issue driving RBG Leds.
>> They were starting turned on full force since the PWM was driving high on
>> boot.
>> Changing the polarity worked for me.
>>
>> Is it possible the order of overlays is undoing your changes to
>> bone_pwm_P8_13?
>> Instead of:
>>
>> cape_enable=capemgr.enable_partno=BB-UART1,SPI-4SS,bone_
>> eqep2b,bone_pwm_P8_13,am33xx_pwm
>>
>> Maybe try it with your modifications being the last overlay to load:
>>
>> cape_enable=capemgr.enable_partno=BB-UART1,SPI-4SS,bone_
>> eqep2b,am33xx_pwm,bone_pwm_P8_13
>>
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Re: [beagleboard] Re: how to make pwm_P8_13 low on boot?

[Miguel Aveiro]

It's not a kernel driver, I believe it's the processor default mode. You 
can check the processor datasheet:

http://www.ti.com/product/AM3359/datasheet/terminal_description?search=pin,default#sprs717824

If you want to change it earlier than linux, you need to set the pin in 
uboot (as far as I can understand). You can check the list because I 
know that I have already read something about change default IO in BBB. 
Or something about u-boot and gpio, like this:

http://www.crashcourse.ca/wiki/index.php/U-Boot_on_the_BBB

Hopefully, this can help a little

Miguel Aveiro

On 25-11-2014 22:28, janszymanski12...@gmail.com wrote:

thanks, unfortunately didn't work for me.

On Wednesday, 26 November 2014 10:02:27 UTC+11, Peter Gregory wrote:

I had the same issue driving RBG Leds.
They were starting turned on full force since the PWM was driving
high on boot.
Changing the polarity worked for me.

Is it possible the order of overlays is undoing your changes to
bone_pwm_P8_13?
Instead of:


cape_enable=capemgr.enable_partno=BB-UART1,SPI-4SS,bone_eqep2b,bone_pwm_P8_13,am33xx_pwm


Maybe try it with your modifications being the last overlay to load:


cape_enable=capemgr.enable_partno=BB-UART1,SPI-4SS,bone_eqep2b,am33xx_pwm,bone_pwm_P8_13


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Re: [beagleboard] Re: how to make pwm_P8_13 low on boot?

[janszymanski12345]

thanks, unfortunately didn't work for me.

On Wednesday, 26 November 2014 10:02:27 UTC+11, Peter Gregory wrote:
>
> I had the same issue driving RBG Leds. 
> They were starting turned on full force since the PWM was driving high on 
> boot. 
> Changing the polarity worked for me. 
>
> Is it possible the order of overlays is undoing your changes to 
> bone_pwm_P8_13? 
> Instead of: 
>
> cape_enable=capemgr.enable_partno=BB-UART1,SPI-4SS,bone_eqep2b,bone_pwm_P8_13,am33xx_pwm
>  
>
>
> Maybe try it with your modifications being the last overlay to load: 
>
> cape_enable=capemgr.enable_partno=BB-UART1,SPI-4SS,bone_eqep2b,am33xx_pwm,bone_pwm_P8_13
>  
>
>

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Re: [beagleboard] Re: how to make pwm_P8_13 low on boot?

[Peter Gregory]

I had the same issue driving RBG Leds.
They were starting turned on full force since the PWM was driving high on boot.
Changing the polarity worked for me.

Is it possible the order of overlays is undoing your changes to bone_pwm_P8_13?
Instead of:

cape_enable=capemgr.enable_partno=BB-UART1,SPI-4SS,bone_eqep2b,bone_pwm_P8_13,am33xx_pwm

Maybe try it with your modifications being the last overlay to load:

cape_enable=capemgr.enable_partno=BB-UART1,SPI-4SS,bone_eqep2b,am33xx_pwm,bone_pwm_P8_13

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Re: [beagleboard] Re: how to make pwm_P8_13 low on boot?

[Jason Lange]

>
> The inverter is not a solution as on boot initial pin value is low and
> after the device tree is loaded it jumps high until the application
> software (controlling pwm) takes over.
> I will use it as a temporary solution.
>
> Cheers
>
> Jan
>
>
> On Wednesday, 26 November 2014 08:45:34 UTC+11, Jason Lange wrote:


- after power on the logic level on P8_13 is low (as I want it to be)
>> - after that (loading dtc overlay) the logic level on P8_13 become high
>> (I dont want it)
>>
>
Sorry, I missed this.  The 74HC04 would work if it started high and stayed
that way.  Do you need to use an overlay?

 *Maybe if you modified the initial device tree, perhaps with Roberts
system for the 3.14 kernel it would start high and you could flip it.*

http://elinux.org/Beagleboard:Capes_3.8_to_3.14#Custom_dtb

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Re: [beagleboard] Re: how to make pwm_P8_13 low on boot?

[janszymanski12345]

 Thanks Jason,

 There is a hardware solution to my problem in a form of a tiny logic 
08 (AND gate). The PWM is connected to one input and an extra ENABLE signal 
from GPIO is connected to another input. On the output the resulting gated 
PWM signal will appear when the ENABLE signal goes high from the 
application.
The solution however is non-elegant and can be avoided if I had a better 
knowledge of the software - in this case a PWM driver and it's interaction 
with a device tree overlay.

The inverter is not a solution as on boot initial pin value is low and 
after the device tree is loaded it jumps high until the application 
software (controlling pwm) takes over.
I will use it as a temporary solution.

Cheers

Jan


On Wednesday, 26 November 2014 08:45:34 UTC+11, Jason Lange wrote:
>
>
>
> - after power on the logic level on P8_13 is low (as I want it to be)
>>> - after that (loading dtc overlay) the logic level on P8_13 become high 
>>> (I dont want it)
>>>
>>
> Sorry, I missed this.  The 74HC04 would work if it started high and stayed 
> that way.  Do you need to use an overlay?  Maybe if you modified the 
> initial device tree, perhaps with Roberts system for the 3.14 kernel it 
> would start high and you could flip it.
>
>  

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[beagleboard] Re: how to make pwm_P8_13 low on boot?

[janszymanski12345]

 Thanks Peter, 

 I have exercised that option already before posting and somehow it didn't 
work.

Changing the parameters (and recompiling) didn't change the default values, 
so my conclusion is that they might be
 
somehow hard-coded in a kernel driver.
Jan

On Monday, 24 November 2014 09:58:19 UTC+11, janszyma...@gmail.com wrote:
>
> Hi,
>
> I'm trying to use pwm on BBB
> Linux beaglebone 3.8.13-bone50 #1 SMP Tue May 13 13:24:52 UTC 2014 armv7l 
> GNU/Linux
> I have modified uEnv.tx
> ...
>
> cape_enable=capemgr.enable_partno=BB-UART1,SPI-4SS,bone_eqep2b,bone_pwm_P8_13,am33xx_pwm
> ...
> and /etc/default/capemgr
> ...
> # Options to pass to capemgr
> CAPE=SPI-4SS,bone_eqep2b,bone_pwm_P8_13,am33xx_pwm
> ...
>
> after booting I have correctly in slots
>  0: 54:PF--- 
>  1: 55:PF--- 
>  2: 56:PF--- 
>  3: 57:PF--- 
>  4: ff:P-O-L Bone-LT-eMMC-2G,00A0,Texas Instrument,BB-BONE-EMMC-2G
>  5: ff:P-O-L Bone-Black-HDMI,00A0,Texas Instrument,BB-BONELT-HDMI
>  7: ff:P-O-L Override Board Name,00A0,Override Manuf,BB-UART1
> 10: ff:P-O-L Override Board Name,00A0,Override Manuf,bone_pwm_P8_13
> 11: ff:P-O-L Override Board Name,00A0,Override Manuf,am33xx_pwm
> 12: ff:P-O-L Override Board Name,00A0,Override Manuf,SPI-4SS
> 13: ff:P-O-L Override Board Name,00A0,Override Manuf,bone_eqep2b
>
> and pwm works, but,
>
> - after power on the logic level on P8_13 is low (as I want it to be)
> - after that (loading dtc overlay) the logic level on P8_13 become high (I 
> dont want it)
>
> My attempt to modify  /lib/firmware/bone_pwm_P8_13-00A0.dts and then 
> recompiling doesn't effect any of:
> /sys/devices/ocp.3/pwm_test_P8_13.11/ duty, period, polarity, run, 
>
> As I don't want the motor connected to PWM to run, before the applications 
> takes over the control,
> can anyone help me to achieve it?
>
> Jan
>
>
>
>

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Re: [beagleboard] Re: how to make pwm_P8_13 low on boot?

[Jason Lange]

- after power on the logic level on P8_13 is low (as I want it to be)
>> - after that (loading dtc overlay) the logic level on P8_13 become high
>> (I dont want it)
>>
>
Sorry, I missed this.  The 74HC04 would work if it started high and stayed
that way.  Do you need to use an overlay?  Maybe if you modified the
initial device tree, perhaps with Roberts system for the 3.14 kernel it
would start high and you could flip it.

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Re: [beagleboard] Re: how to make pwm_P8_13 low on boot?

[Jason Lange]

>From hardware you could use a 74HC04 to invert the signal.  No need for an
additional enable line.

Cheers.

On Tue, Nov 25, 2014 at 1:27 PM, ja...@bigpond.net.au 
wrote:

>
>  Thanks Peter,
>
>  I have exercised that option already before posting and somehow it didn't
> work.
>
> Changing the parameters (and recompiling) didn't change the default
> values, so my conclusion is that they might be
>
> somehow hard-coded in a kernel driver.
>
> Jan
> --
> On 26/11/2014 12:34 AM Peter Gregory wrote:
>
> I don't know if this will help, but have you tried changing the polarity
> of the PWM pin in the device tree overlay?
>
> bs_pwm_test_P8_13 {
> compatible = "pwm_test";
> pwms = <&ehrpwm2 1 50 0>;
> pwm-names = "PWM_P8_13";
>
> pinctrl-names = "default";
> pinctrl-0 = <&bs_pwm_P8_13_0xc>;
>
> enabled = <1>;
> duty = <0>;
> status = "okay";
> };
>
>
> The last numeric parameter of pwms <&ehrpwm2 1 50 0> swaps the
> polarity of the PWM output.
> With the default duty cycle of 0, the pin will be low on power-up.
>
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Re: [beagleboard] Re: how to make pwm_P8_13 low on boot?

[ja...@bigpond.net.au]

  Thanks Peter, I have exercised that option already before posting and somehow it didn't work.Changing the parameters (and recompiling) didn't change the default values, so my conclusion is that they might be somehow hard-coded in a kernel driver.JanOn 26/11/2014 12:34 AM Peter Gregory  wrote:I don't know if this will help, but have you tried changing the polarity of the PWM pin in the device tree overlay?	bs_pwm_test_P8_13 {		compatible	= "pwm_test";		pwms 		= <&ehrpwm2 1 50 0>;		pwm-names 	= "PWM_P8_13";		pinctrl-names	= "default";		pinctrl-0	= <&bs_pwm_P8_13_0xc>;		enabled		= <1>;		duty		= <0>;		status 		= "okay";	};The last numeric parameter of pwms  <&ehrpwm2 1 50 0> swaps the polarity of the PWM output.With the default duty cycle of 0, the pin will be low on power-up.-- For more options, visit http://beagleboard.org/discuss--- You received this message because you are subscribed to a topic in the Google Groups "BeagleBoard" group.To unsubscribe from this topic, visit https://groups.google.com/d/topic/beagleboard/bqsOg6NMyIM/unsubscribe.To unsubscribe from this group and all its topics, send an email to beagleboard+unsubscr...@googlegroups.com.For more options, visit https://groups.google.com/d/optout.



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[beagleboard] Re: how to make pwm_P8_13 low on boot?

[Peter Gregory]

I don't know if this will help, but have you tried changing the polarity of the 
PWM pin in the device tree overlay?

bs_pwm_test_P8_13 {
compatible  = "pwm_test";
pwms= <&ehrpwm2 1 50 0>;
pwm-names   = "PWM_P8_13";

pinctrl-names   = "default";
pinctrl-0   = <&bs_pwm_P8_13_0xc>;

enabled = <1>;
duty= <0>;
status  = "okay";
};


The last numeric parameter of pwms  <&ehrpwm2 1 50 0> swaps the polarity of 
the PWM output.
With the default duty cycle of 0, the pin will be low on power-up.

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[beagleboard] Re: how to make pwm_P8_13 low on boot?

[janszymanski12345]

the values in /sys/devices/ocp.3/pwm_test_P8_13/11 are:
duty 0
period 50
polarity 1
run 1
after the device tree overlay is loaded.
Does anyone know if possible and if yes how to change them (the default 
values)?
The changes to corresponding *.dtbo file doesn't change them.


On Monday, 24 November 2014 09:58:19 UTC+11, janszyma...@gmail.com wrote:
>
> Hi,
>
> I'm trying to use pwm on BBB
> Linux beaglebone 3.8.13-bone50 #1 SMP Tue May 13 13:24:52 UTC 2014 armv7l 
> GNU/Linux
> I have modified uEnv.tx
> ...
>
> cape_enable=capemgr.enable_partno=BB-UART1,SPI-4SS,bone_eqep2b,bone_pwm_P8_13,am33xx_pwm
> ...
> and /etc/default/capemgr
> ...
> # Options to pass to capemgr
> CAPE=SPI-4SS,bone_eqep2b,bone_pwm_P8_13,am33xx_pwm
> ...
>
> after booting I have correctly in slots
>  0: 54:PF--- 
>  1: 55:PF--- 
>  2: 56:PF--- 
>  3: 57:PF--- 
>  4: ff:P-O-L Bone-LT-eMMC-2G,00A0,Texas Instrument,BB-BONE-EMMC-2G
>  5: ff:P-O-L Bone-Black-HDMI,00A0,Texas Instrument,BB-BONELT-HDMI
>  7: ff:P-O-L Override Board Name,00A0,Override Manuf,BB-UART1
> 10: ff:P-O-L Override Board Name,00A0,Override Manuf,bone_pwm_P8_13
> 11: ff:P-O-L Override Board Name,00A0,Override Manuf,am33xx_pwm
> 12: ff:P-O-L Override Board Name,00A0,Override Manuf,SPI-4SS
> 13: ff:P-O-L Override Board Name,00A0,Override Manuf,bone_eqep2b
>
> and pwm works, but,
>
> - after power on the logic level on P8_13 is low (as I want it to be)
> - after that (loading dtc overlay) the logic level on P8_13 become high (I 
> dont want it)
>
> My attempt to modify  /lib/firmware/bone_pwm_P8_13-00A0.dts and then 
> recompiling doesn't effect any of:
> /sys/devices/ocp.3/pwm_test_P8_13.11/ duty, period, polarity, run, 
>
> As I don't want the motor connected to PWM to run, before the applications 
> takes over the control,
> can anyone help me to achieve it?
>
> Jan
>
>
>
>

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