On Sun, 29 Dec 2013, Josiah Morgan wrote:

> Date: Sun, 29 Dec 2013 11:07:53 -0600
> From: Josiah Morgan <[email protected]>
> Reply-To: "Enhanced Machine Controller (EMC)"
>     <[email protected]>
> To: "Enhanced Machine Controller (EMC)" <[email protected]>
> Subject: Re: [Emc-users] linuxCNC BBB capeless
> 
> Charles,
> Thanks again for the help.
> Reading the manual for the vfd, it looks like the input is a frequency
> pulse train rather than pwm to control spindle speed.  Is there a simple
> way to generate a variable frequency pulse to control spindle speed rather
> than using the pulse width modulation?
> Thanks

If the PRU stepgen is like most of the LinuxCNC stepgens, you should be able 
to use a stepgen in velocity mode as a rate generator for the spindle



>
> On Saturday, December 28, 2013, Charles Steinkuehler wrote:
>
>> On 12/28/2013 10:51 AM, Josiah Morgan wrote:
>>> thank you for the quick response.
>>> I will look into making those changes.
>>> the spindle will be using a  hitachi x200 vfd.  there will be no need for
>>> any kind of feedback.
>>
>> So you're all set as far as PRU and BeagleBone code goes, nothing needs
>> to get written.
>>
>>> I'm guessing I'll have to somehow define in the setup what kind of signal
>>> to send the vfd on what pin when the machine code interpreter sees S code
>>> or M codes?
>>> thanks.
>>
>> Yes, and everything up to the actual PWM driver is the same setup you
>> would need for any other LinuxCNC install.  The PWM driver for the
>> BeagleBone PRU is modeled after the hostmot2 pwmgen and is intended to
>> behave identically.  There are three PWM generators instantiated in all
>> my example configurations, but you can change this as you see fit (using
>> the num_pwmgens= setting).
>>
>> To connect/control the PWM generators, use the following:
>>
>> Pins:
>> hal_pru_generic.pwmgen.00.out.00.enable
>> hal_pru_generic.pwmgen.00.out.00.value
>>
>> Parameters:
>> hal_pru_generic.pwmgen.00.out.00.pin
>> hal_pru_generic.pwmgen.00.out.00.scale
>>
>> For additional instances, the second "00" increments, ie:
>> hal_pru_generic.pwmgen.00.out.00.value
>> hal_pru_generic.pwmgen.00.out.01.value
>> hal_pru_generic.pwmgen.00.out.02.value
>> ...
>>
>> You are responsible for converting the 3.3V digital signal that appears
>> on the BeagleBone P8/P9 header into something your VFD will accept as an
>> input.  Holler if you need help with this, or if a generic PWM generator
>> is not an appropriate control signal.
>>
>> --
>> Charles Steinkuehler
>> [email protected] <javascript:;>
>>
>>
>
> -- 
> Josiah Morgan, P.E.
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Mesa Electronics

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