[beagleboard] Re: PWM: changing Period of EHRPWM

[avterekhov]

Hi,

In case someone still needs a solution to this problem, I've written a 
small kernel patch: ti_ehr_pwm.patch 
 and a short 
description of how to apply it: 
https://randomlinuxhacks.wordpress.com/2014/09/16/changing-pwm-period-on-beaglebone-black/

So far it works for me.

On Thursday, June 26, 2014 8:10:26 AM UTC+2, jmc...@gmail.com wrote:
>
> I also tried this and had no luck :-/
>
> PWM on the BBB is turning out to be more work than I had thought.
>
> On Monday, January 6, 2014 12:13:37 PM UTC-8, Anto Dominic wrote:
>>
>> Thanks,
>>
>> Tried your trick even replaced the new dtbo file but even after 
>> that I am getting the default value for Period ( ie, 500) and duty (ie, 
>> 0) ... Is there any step that you missed in between...??. Anyways thanks 
>> for the tip..:)
>>
>> On Monday, 8 July 2013 08:44:54 UTC+5:30, tohr...@gmail.com wrote:
>>>
>>> Hello,
>>>
>>> you can change period by changing dtbo files.
>>>
>>> 1 Generate dts file from original dtbo file
>>> dtc -I dtb -O dts -o /lib/firmware/bone_pwm_P8_13-00A0.dts /lib/firmware
>>> /bone_pwm_P8_13-00A0.dtbo
>>>
>>> 2 Change period
>>> open file "/lib/firmware/bone_pwm_P8_13-00A0.dts" with editor at 
>>> lines around line 26:
>>> pwm_test_P8_13 {
>>> compatible = "pwm_test";
>>> pwms = <0xdeadbeef 0x1 0x7a120 0x1>;
>>>
>>>  and change to following, for example change period to 10ns=0.1ms
>>>
>>> pwm_test_P8_13 {
>>> compatible = "pwm_test";
>>> pwms = <0xdeadbeef 0x1 10 0x1>;
>>>   
>>> where
>>> -3rd parameter of line"pwms = ~" is period.
>>> -period (and other parameters) can be written in either decimal or 
>>> hexadecimal of 0xABC format.
>>> -default period 0x7a120 is 500 in decimal.
>>> -As you mentioned, Both A and B output for one eHRPWM must have same 
>>> period setting.
>>>  If not, the second device will fail to setup at "echo (device)> 
>>> /sys/devices/bone_capemgr.*/slots" command.
>>>
>>> 3 Compile to new dtbo file
>>> dtc -O dtb -o bone_pwm_P8_13-00A0.dtbo -b 0 -@ bone_pwm_P8_13-00A0.dts
>>>
>>>  You'd better back up original dtbo file before overwriting it.
>>>
>>> 4 Use new dtbo file. 
>>> echo bone_pwm_P8_13 > /sys/devices/bone_capemgr.*/slots
>>>
>>>
>>>
>>> 2013年6月4日火曜日 16時33分00秒 UTC+9 sultanof.ilo...@gmail.com:

 Hey, 
 yes sure, duty must be (0 <= duty <= period). Otherwise you would try 
 to to set a pwm duty cycle of less than 0% or more than 100%. Returning an 
 error to the user is a proper way to handle this. 

 As mentioned above EHRPWM1 and EHRPWM2 share the same base period (or 
 respectively the base frequency). If I enable both PWM ouputs, writing to 
 the period files always results in an error. Enabeling only one of the two 
 outputs lets me change the periods.
 This does make sense after all. I assume the necessary crosschecking of 
 the conditions (0 <= duty <= period) for related PWM outputs is simply not 
 implemented yet or mayby just faulty. 

 Am Montag, 3. Juni 2013 12:25:15 UTC+2 schrieb lawe...@gmail.com:
>
> Hi
>
> I'm just starting out, but here is what I found. Hopefully it can help 
> you.
> The period must be greater than duty.
> This worked fine for me:
> echo 10 > /sys/devices/ocp.2/pwm_test_P9_14.12/period
> Period is given in ns. Duty is given in ns on/off depending on 
> polarity.
>

>>>

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[beagleboard] Re: PWM: changing Period of EHRPWM

[jmc5113]

I also tried this and had no luck :-/

PWM on the BBB is turning out to be more work than I had thought.

On Monday, January 6, 2014 12:13:37 PM UTC-8, Anto Dominic wrote:
>
> Thanks,
>
> Tried your trick even replaced the new dtbo file but even after 
> that I am getting the default value for Period ( ie, 500) and duty (ie, 
> 0) ... Is there any step that you missed in between...??. Anyways thanks 
> for the tip..:)
>
> On Monday, 8 July 2013 08:44:54 UTC+5:30, tohr...@gmail.com wrote:
>>
>> Hello,
>>
>> you can change period by changing dtbo files.
>>
>> 1 Generate dts file from original dtbo file
>> dtc -I dtb -O dts -o /lib/firmware/bone_pwm_P8_13-00A0.dts /lib/firmware/
>> bone_pwm_P8_13-00A0.dtbo
>>
>> 2 Change period
>> open file "/lib/firmware/bone_pwm_P8_13-00A0.dts" with editor at 
>> lines around line 26:
>> pwm_test_P8_13 {
>> compatible = "pwm_test";
>> pwms = <0xdeadbeef 0x1 0x7a120 0x1>;
>>
>>  and change to following, for example change period to 10ns=0.1ms
>>
>> pwm_test_P8_13 {
>> compatible = "pwm_test";
>> pwms = <0xdeadbeef 0x1 10 0x1>;
>>   
>> where
>> -3rd parameter of line"pwms = ~" is period.
>> -period (and other parameters) can be written in either decimal or 
>> hexadecimal of 0xABC format.
>> -default period 0x7a120 is 500 in decimal.
>> -As you mentioned, Both A and B output for one eHRPWM must have same 
>> period setting.
>>  If not, the second device will fail to setup at "echo (device)> 
>> /sys/devices/bone_capemgr.*/slots" command.
>>
>> 3 Compile to new dtbo file
>> dtc -O dtb -o bone_pwm_P8_13-00A0.dtbo -b 0 -@ bone_pwm_P8_13-00A0.dts
>>
>>  You'd better back up original dtbo file before overwriting it.
>>
>> 4 Use new dtbo file. 
>> echo bone_pwm_P8_13 > /sys/devices/bone_capemgr.*/slots
>>
>>
>>
>> 2013年6月4日火曜日 16時33分00秒 UTC+9 sultanof.ilo...@gmail.com:
>>>
>>> Hey, 
>>> yes sure, duty must be (0 <= duty <= period). Otherwise you would try to 
>>> to set a pwm duty cycle of less than 0% or more than 100%. Returning an 
>>> error to the user is a proper way to handle this. 
>>>
>>> As mentioned above EHRPWM1 and EHRPWM2 share the same base period (or 
>>> respectively the base frequency). If I enable both PWM ouputs, writing to 
>>> the period files always results in an error. Enabeling only one of the two 
>>> outputs lets me change the periods.
>>> This does make sense after all. I assume the necessary crosschecking of 
>>> the conditions (0 <= duty <= period) for related PWM outputs is simply not 
>>> implemented yet or mayby just faulty. 
>>>
>>> Am Montag, 3. Juni 2013 12:25:15 UTC+2 schrieb lawe...@gmail.com:

 Hi

 I'm just starting out, but here is what I found. Hopefully it can help 
 you.
 The period must be greater than duty.
 This worked fine for me:
 echo 10 > /sys/devices/ocp.2/pwm_test_P9_14.12/period
 Period is given in ns. Duty is given in ns on/off depending on polarity.

>>>
>>

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[beagleboard] Re: PWM: changing Period of EHRPWM

[Giuseppe Iellamo]

Hi,

the problem is a bug in pwm_test so that once you enabled two channels of 
the same ehrpwm you cannot change the period.

Try look at

http://saadahmad.ca/using-pwm-on-the-beaglebone-black/

https://github.com/SaadAhmad/beaglebone-black-cpp-PWM

Il giorno lunedì 6 gennaio 2014 21:13:37 UTC+1, anto...@gmail.com ha 
scritto:
>
> Thanks,
>
> Tried your trick even replaced the new dtbo file but even after 
> that I am getting the default value for Period ( ie, 500) and duty (ie, 
> 0) ... Is there any step that you missed in between...??. Anyways thanks 
> for the tip..:)
>
> On Monday, 8 July 2013 08:44:54 UTC+5:30, tohr...@gmail.com wrote:
>>
>> Hello,
>>
>> you can change period by changing dtbo files.
>>
>> 1 Generate dts file from original dtbo file
>> dtc -I dtb -O dts -o /lib/firmware/bone_pwm_P8_13-00A0.dts /lib/firmware/
>> bone_pwm_P8_13-00A0.dtbo
>>
>> 2 Change period
>> open file "/lib/firmware/bone_pwm_P8_13-00A0.dts" with editor at 
>> lines around line 26:
>> pwm_test_P8_13 {
>> compatible = "pwm_test";
>> pwms = <0xdeadbeef 0x1 0x7a120 0x1>;
>>
>>  and change to following, for example change period to 10ns=0.1ms
>>
>> pwm_test_P8_13 {
>> compatible = "pwm_test";
>> pwms = <0xdeadbeef 0x1 10 0x1>;
>>   
>> where
>> -3rd parameter of line"pwms = ~" is period.
>> -period (and other parameters) can be written in either decimal or 
>> hexadecimal of 0xABC format.
>> -default period 0x7a120 is 500 in decimal.
>> -As you mentioned, Both A and B output for one eHRPWM must have same 
>> period setting.
>>  If not, the second device will fail to setup at "echo (device)> 
>> /sys/devices/bone_capemgr.*/slots" command.
>>
>> 3 Compile to new dtbo file
>> dtc -O dtb -o bone_pwm_P8_13-00A0.dtbo -b 0 -@ bone_pwm_P8_13-00A0.dts
>>
>>  You'd better back up original dtbo file before overwriting it.
>>
>> 4 Use new dtbo file. 
>> echo bone_pwm_P8_13 > /sys/devices/bone_capemgr.*/slots
>>
>>
>>
>> 2013年6月4日火曜日 16時33分00秒 UTC+9 sultanof.ilo...@gmail.com:
>>>
>>> Hey, 
>>> yes sure, duty must be (0 <= duty <= period). Otherwise you would try to 
>>> to set a pwm duty cycle of less than 0% or more than 100%. Returning an 
>>> error to the user is a proper way to handle this. 
>>>
>>> As mentioned above EHRPWM1 and EHRPWM2 share the same base period (or 
>>> respectively the base frequency). If I enable both PWM ouputs, writing to 
>>> the period files always results in an error. Enabeling only one of the two 
>>> outputs lets me change the periods.
>>> This does make sense after all. I assume the necessary crosschecking of 
>>> the conditions (0 <= duty <= period) for related PWM outputs is simply not 
>>> implemented yet or mayby just faulty. 
>>>
>>> Am Montag, 3. Juni 2013 12:25:15 UTC+2 schrieb lawe...@gmail.com:

 Hi

 I'm just starting out, but here is what I found. Hopefully it can help 
 you.
 The period must be greater than duty.
 This worked fine for me:
 echo 10 > /sys/devices/ocp.2/pwm_test_P9_14.12/period
 Period is given in ns. Duty is given in ns on/off depending on polarity.

>>>
>>

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[beagleboard] Re: PWM: changing Period of EHRPWM

[antodoms]

Thanks,

Tried your trick even replaced the new dtbo file but even after 
that I am getting the default value for Period ( ie, 500) and duty (ie, 
0) ... Is there any step that you missed in between...??. Anyways thanks 
for the tip..:)

On Monday, 8 July 2013 08:44:54 UTC+5:30, tohr...@gmail.com wrote:
>
> Hello,
>
> you can change period by changing dtbo files.
>
> 1 Generate dts file from original dtbo file
> dtc -I dtb -O dts -o /lib/firmware/bone_pwm_P8_13-00A0.dts /lib/firmware/
> bone_pwm_P8_13-00A0.dtbo
>
> 2 Change period
> open file "/lib/firmware/bone_pwm_P8_13-00A0.dts" with editor at lines 
> around line 26:
> pwm_test_P8_13 {
> compatible = "pwm_test";
> pwms = <0xdeadbeef 0x1 0x7a120 0x1>;
>
>  and change to following, for example change period to 10ns=0.1ms
>
> pwm_test_P8_13 {
> compatible = "pwm_test";
> pwms = <0xdeadbeef 0x1 10 0x1>;
>   
> where
> -3rd parameter of line"pwms = ~" is period.
> -period (and other parameters) can be written in either decimal or 
> hexadecimal of 0xABC format.
> -default period 0x7a120 is 500 in decimal.
> -As you mentioned, Both A and B output for one eHRPWM must have same 
> period setting.
>  If not, the second device will fail to setup at "echo (device)> 
> /sys/devices/bone_capemgr.*/slots" command.
>
> 3 Compile to new dtbo file
> dtc -O dtb -o bone_pwm_P8_13-00A0.dtbo -b 0 -@ bone_pwm_P8_13-00A0.dts
>
>  You'd better back up original dtbo file before overwriting it.
>
> 4 Use new dtbo file. 
> echo bone_pwm_P8_13 > /sys/devices/bone_capemgr.*/slots
>
>
>
> 2013年6月4日火曜日 16時33分00秒 UTC+9 sultanof.ilo...@gmail.com:
>>
>> Hey, 
>> yes sure, duty must be (0 <= duty <= period). Otherwise you would try to 
>> to set a pwm duty cycle of less than 0% or more than 100%. Returning an 
>> error to the user is a proper way to handle this. 
>>
>> As mentioned above EHRPWM1 and EHRPWM2 share the same base period (or 
>> respectively the base frequency). If I enable both PWM ouputs, writing to 
>> the period files always results in an error. Enabeling only one of the two 
>> outputs lets me change the periods.
>> This does make sense after all. I assume the necessary crosschecking of 
>> the conditions (0 <= duty <= period) for related PWM outputs is simply not 
>> implemented yet or mayby just faulty. 
>>
>> Am Montag, 3. Juni 2013 12:25:15 UTC+2 schrieb lawe...@gmail.com:
>>>
>>> Hi
>>>
>>> I'm just starting out, but here is what I found. Hopefully it can help 
>>> you.
>>> The period must be greater than duty.
>>> This worked fine for me:
>>> echo 10 > /sys/devices/ocp.2/pwm_test_P9_14.12/period
>>> Period is given in ns. Duty is given in ns on/off depending on polarity.
>>>
>>
>

-- 
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