On 9/22/2016 12:21 PM, Sag ich Dir nich wrote:
> so now i added a scale (which is maximum rpm) and i can command various 
> speeds 
> but still the motor vibrates. somehow it sounds like it ramps up and down a 
> bit 
> when commanding for example 2000rpm. Noise could probably be, i may change 
> the 
> output to another port (had some coordinate moves with various spindle speeds 
> and when one axis changed direction, the motor stopped for a few 
> milliseconds), 
> is there any pin i can use for pwm that has 5v output on its own?

The PRU generated PWM output is fairly low frequency.  You may need to
increase the PWM frequency (which will decrease the available
resolution) or use one of the hardware PWM outputs.  I don't think
there is a HAL driver to talk directly to the BBB's hardware PWM
channels, but for spindle speed a user-mode python script should work

There is nothing on the BBB that generates a 5V output (3.3V only),
and no 5V buffered outputs on the CRAMPS boards (just the FET outputs).

If there is an analog input to your motor control, you could craft a
low-pass filter and the low-speed PWM wouldn't matter that much.

> what do you mean by "pull-up"?

A pull-up resistor to 5V.  A resistor between the FET output and the
power rail to pull the output high when the FET turns off.

Charles Steinkuehler

website: http://www.machinekit.io blog: http://blog.machinekit.io github: 
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