The reason I wanted to use the PRU was that we need to send a fixed
number of pulses to the servo motors. We tried it with the usual PWM
channels on the beaglebone and by the time we are done counting the
number and disabling the PWM, the servo ends up receiving a few extra
pulses and overshooting. Maybe comparing it in a while loop is not such
a great idea. If there is a better way that does not involve the use of
PRUs, I would readily switch to that.
Also, Mark, a small part I didn’t understand in |pru-pwm.asm|. Once you
load the period and duty cycle in |channel|, only some should get either
enabled or disabled each cycle. How do you decide which ones to set high
and low?
Adwait
On Thursday 08 June 2017 06:55 AM, Mark A. Yoder wrote:
Last summer I did a project where I programmed the PRUs to provide an
18 channel PWM (12 on one PRU and 6 on the other). Each could have
it's own frequency and duty cycle.
The details are here[1].
Though I think using the PRUs may be overkill for what you need to do.
There are several hardware PWM channels on the Bone that don't need
the PRUs.
--Mark
[1] https://github.com/MarkAYoder/BeagleBoard-exercises/tree/master/pru/examples/pwm
On Wednesday, June 7, 2017 at 12:24:08 PM UTC-4, Adwait wrote:
Sorry, forgot to mention that. I'll be running 2 servo motors and
2 brush-less dc motors.
I am concerned about the fact that all of them will be running at
different frequencies and in parallel. So far I can only think of
running them one after the other. Is there a way to thread in a PRU?
I'll have a look at the link you mentioned and see if it helps.
Thanks
On Wednesday 07 June 2017 08:51 PM, TJF wrote:
Hi Adwait!
Don't you think you should give us an idea of what kind of motors
you're talking about (stepper, serve, ???).
For bit-banging you don't need the PRU at all. Several modules
can generate PWM output, like PWM modules and CAP modules in the
PWMSS, or the TIMER subsystems. libpruio
<http://beagleboard.org/project/libpruio/> offers easy (but also
the most flexible) acces to that capabilities.
Regards
--
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