Logic level for PWM, kernel 4.1?

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Hồng Quân Nguyễn

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Sep 20, 2016, 4:48:08 AM9/20/16
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Hi,

Is there any way to configure logic level for PWM on BeagleBone Black/Green? I want that in duty cycle, the level of pinout is 0V, instead of 3.3V.

I'm using Debian 8 with kernel 4.1.

evilwulfie

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Sep 20, 2016, 9:40:45 AM9/20/16
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you are not making sense.

pwm pin low - 0v high = 3.3 v
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Nguyễn Hồng Quân

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Sep 20, 2016, 10:07:18 AM9/20/16
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What I want is, after "reset", the servo motor is supposed to be off, the pin is 3.3V, and when PWM starts, the servo is supposed to be started, the pin is 0V.

On Tue, Sep 20, 2016 at 8:40 PM, evilwulfie <evilw...@gmail.com> wrote:

you are not making sense.

pwm pin low - 0v high = 3.3 v




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Robert Nelson

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Sep 20, 2016, 10:21:22 AM9/20/16
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On Tue, Sep 20, 2016 at 9:06 AM, Nguyễn Hồng Quân <ng.hon...@gmail.com> wrote:
What I want is, after "reset", the servo motor is supposed to be off, the pin is 3.3V, and when PWM starts, the servo is supposed to be started, the pin is 0V.


Stick an inverter in there. 

Regards, 

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Nguyễn Hồng Quân

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Sep 20, 2016, 10:25:33 AM9/20/16
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Hi Robert,

So there is no way to config the pin? I want the pin to be 0V when PWM is working, because I want to reduce the power drain from my BeagleBone board to feed the PWM pin. It is similar to why we have GPIO at 0V to turn on the LED.

On Tue, Sep 20, 2016 at 9:20 PM, Robert Nelson <robert...@gmail.com> wrote:

On Tue, Sep 20, 2016 at 9:06 AM, Nguyễn Hồng Quân <ng.hon...@gmail.com> wrote:
What I want is, after "reset", the servo motor is supposed to be off, the pin is 3.3V, and when PWM starts, the servo is supposed to be started, the pin is 0V.


Stick an inverter in there. 


evilwulfie

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Sep 20, 2016, 10:29:28 AM9/20/16
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you will need an external inverting buffer
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Gerald Coley

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Sep 20, 2016, 10:50:56 AM9/20/16
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Read the datasheet. It will tell you the state of the pin after reset, before the SW has run.

Gerald

On Tue, Sep 20, 2016 at 9:29 AM, evilwulfie <evilw...@gmail.com> wrote:



you will need an external inverting buffer



On 9/20/2016 7:06 AM, Nguyễn Hồng Quân wrote:
What I want is, after "reset", the servo motor is supposed to be off, the pin is 3.3V, and when PWM starts, the servo is supposed to be started, the pin is 0V.

On Tue, Sep 20, 2016 at 8:40 PM, evilwulfie <evilw...@gmail.com> wrote:

you are not making sense.

pwm pin low - 0v high = 3.3 v




--
Quân
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Nguyễn Hồng Quân

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Sep 20, 2016, 11:02:22 AM9/20/16
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On Tue, Sep 20, 2016 at 9:50 PM, Gerald Coley <ger...@beagleboard.org> wrote:

Read the datasheet. It will tell you the state of the pin after reset, before the SW has run..

I don't really care the status in short moment. The reason behind my question is:

"
​I want the pin to be 0V when PWM is working, because I want to reduce the power drain from my BeagleBone board to feed the PWM pin. It is similar to why we have GPIO at 0V to turn on the LED."

It will be good if you can point me where to read in the datasheet. I feel difficulty reading the whole document.

Gerald Coley

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Sep 20, 2016, 11:07:21 AM9/20/16
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Do a PDF search for the pin number. 

Gerald


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Graham

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Sep 20, 2016, 11:21:31 AM9/20/16
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If you don't care about the initial state and when Linux is booting, why don't you just invert
the duty cycle in software?  That would effectively invert the pin polarity.
--- Graham

==


On Tuesday, September 20, 2016 at 10:07:21 AM UTC-5, Gerald wrote:
Do a PDF search for the pin number. 

Gerald

On Tue, Sep 20, 2016 at 10:02 AM, Nguyễn Hồng Quân <ng.hon...@gmail.com> wrote:


On Tue, Sep 20, 2016 at 9:50 PM, Gerald Coley <ger...@beagleboard.org> wrote:

Read the datasheet. It will tell you the state of the pin after reset, before the SW has run..

I don't really care the status in short moment. The reason behind my question is:

"
​I want the pin to be 0V when PWM is working, because I want to reduce the power drain from my BeagleBone board to feed the PWM pin. It is similar to why we have GPIO at 0V to turn on the LED."

It will be good if you can point me where to read in the datasheet. I feel difficulty reading the whole document.

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Quân
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* Facebook: ng.hong.quan                      *
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