[MinnowBoard] PWM problem

[Oshrat, Yinon]

That explain it.
I was hoping to control a servo motor, which need a control signal of 50Hz=20ms.
Anyone know of a good way to achieve this?

-----Original Message-----
From: Darren Hart [mailto:dvhart at linux.intel.com] 
Sent: Monday, July 6, 2015 9:07 PM
To: MinnowBoard Development and Community Discussion
Cc: Oshrat, Yinon
Subject: Re: [MinnowBoard] PWM problem

On 7/6/15, 5:13 AM, "elinux-MinnowBoard on behalf of Oshrat, Yinon"
<elinux-minnowboard-bounces at lists.elinux.org on behalf of yinon.oshrat at intel.com> wrote:

>'what bios/kernel version are you using?
>No matter what value I use as period, it always stays 1.3 ms


Which values are you trying? By my calculations, the maximum period supported by the hardware is 2.6ms, although in practice I haven't seen it go beyond 1.3 ms. I believe the currently supported range is 80ns to 1.3ms. If you are trying values larger than 1.3ms, then it will not make a difference. The E3800 datasheet [1] provides PWM register documentation (Chapter 28), and the attached screenshot is a worksheet I put together to determine the possible values.

Thanks,

Darren

1. 
http://www.intel.com/content/www/us/en/embedded/products/bay-trail/atom-e38
00-family-datasheet.html

>
>-----Original Message-----
>From: elinux-MinnowBoard
>[mailto:elinux-minnowboard-bounces at lists.elinux.org] On Behalf Of 
>Markus Maier
>Sent: Monday, July 6, 2015 12:03 PM
>To: elinux-minnowboard at lists.elinux.org
>Subject: Re: [MinnowBoard] PWM problem
>
>Oshrat, Yinon <yinon.oshrat at ...> writes:
>
>> 
>> 
>> 
>> Hi,
>> Sorry to bother the group, but maybe someone know how to use PWM, I 
>> have
>the issue described below and couldn't find a solution.
>>  
>> Thanks
>> Yinon
>>  
>> 
>> 
>> From: elinux-MinnowBoard [mailto:elinux-minnowboard-bounces <at>
>lists.elinux.org]
>> On Behalf Of Oshrat, YinonSent: Thursday, June 25, 2015 2:01 PMTo:
>elinux-minnowboard-XmKyDsxDEzZ74goWV3ctuw at public.gmane.orgSubject:
>[MinnowBoard] PWM problem
>> 
>> 
>>  
>> Hi,
>> I try to use the PWM GPIOs of a Minnowboard MAX and encounter a problem.
>> No matter what the value I write into 
>> /sys/class/pwm/pwmchip0/pwm0/period
>> The output signal period is the same, about 1.3ms Did anyone 
>> encounterd this problem? Is there a way to fix that?
>>  
>> I use Ubuntu with kernel 3.19.0-15-generic
>>  
>> Thanks
>> Yinon
>>  
>>  
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>
>
>Hi Yinon,
>
>I did something like
>
>--------
># make PWM available
>echo 0 > /sys/class/pwm/pwmchip0/export
>
># set period to 40µs
>echo 40000 > /sys/class/pwm/pwmchip0/pwm0/period
>
># set the duty cycle
>echo 20000 > /sys/class/pwm/pwmchip0/pwm0/duty_cycle
>
># enable the PWM
>echo 1 > /sys/class/pwm/pwmchip0/pwm0/enable
>--------
>
>Works for me...
>
>Cheers
>Markus
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>elinux-MinnowBoard at lists.elinux.org
>http://lists.elinux.org/mailman/listinfo/elinux-minnowboard
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--
Darren Hart
Intel Open Source Technology Center


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