Re: [Emc-users] linuxCNC BBB capeless

[Charles S. <ch...@st...>]

My step/dir generators are modeled after the hostmot2 components and
generally have identical pins, ports, and behavior (at least that was my
goal), so you control velocity or position mode with the control-type
pin, ie:

hal_pru_generic.stepgen.00.control-type

See also:
http://www.linuxcnc.org/docs/html/man/man9/hostmot2.9.html#stepgen

...not everything is supported (the PRU currently only does step/dir
mode, not up/down or quadrature), but I tried to make all supported
controls identical in function to hm2.  The idea is to make it easy to
go between a BeagleBone PRU configuration and an x86 (or BeagleBone with
FPGA when that becomes available!) running with hostmot2 for higher
performance.

On 12/30/2013 9:16 PM, Josiah Morgan wrote:
> Thanks again for the suggestions. I feel like I am making headway.
> However, I can't seem to figure out how to set one of the Stepgens to
> velocity mode since they are all created together via some pru_generic.bin
> file.
> Is there a way to pass this argument to this bin file or is there a way to
> bypass the bin file and just create the stepgen on the fly?
> 
> On Sunday, December 29, 2013, Charles Steinkuehler wrote:
> 
>> On 12/29/2013 11:30 AM, Peter C. Wallace wrote:
>>> On Sun, 29 Dec 2013, Josiah Morgan wrote:
>>>
>>>> Date: Sun, 29 Dec 2013 11:07:53 -0600
>>>> From: Josiah Morgan <jos...@gm... <javascript:;>>
>>>> Reply-To: "Enhanced Machine Controller (EMC)"
>>>>     <emc...@li... <javascript:;>>
>>>> To: "Enhanced Machine Controller (EMC)" <
>> emc...@li... <javascript:;>>
>>>> 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
>>
>> Yes, the PRU stepgens will run in velocity mode, which is a good way to
>> get a programmable frequency generator.  The only caveat is your pulse
>> width will be fixed so the duty cycle will change with frequency.  If
>> that is OK with your VFD you're all set.  If not, I'll probably have to
>> code up a frequency generator task for the PRU, unless the required
>> frequency is low enough (below 200-300 Hz or so) you can generate it in
>> the 1 KHz servo thread using the HAL software frequency generator.
>>
>> --
>> Charles Steinkuehler
>> ch...@st... <javascript:;>
>>
>>
> 


-- 
Charles Steinkuehler
ch...@st...