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, 5000000) 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 100000ns=0.1ms
>>
>> pwm_test_P8_13 {
>> compatible = "pwm_test";
>> pwms = <0xdeadbeef 0x1 100000 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 5000000 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 100000 > /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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