Re: [Xenomai] Xenomai on Raspberry pi 2, 3 - Userspace task is interrupted?

[Greg Gallagher <greg@embeddedgreg.com>]

How are you setting up the gpio read and write? Is it possible to post a code snippet for the read and write?

Greg

  Original Message  
From: mophong@gmail.com
Sent: August 8, 2018 6:45 AM
To: xenomai@xenomai.org
Reply-to: mophong@gmail.com
Subject: [Xenomai] Xenomai on Raspberry pi 2, 3 - Userspace task is interrupted?

Hello all,
I make a simple code to measure process time on Raspberry pi 0,1,2,3 like:

* previous = rt_timer_read();*
* for (i=0; i<500; ++i)*
* {*
* bcm2835_gpio_write(TEST_PIN, HIGH);*
* bcm2835_gpio_write(TEST_PIN, LOW);*
* }*
* now = rt_timer_read();*
* process_time = (long) (now - previous);*
* if (process_time>worst_time)*
* worst_time=process_time;*

And I result after several hours running:
rpi           process_time (us)             worst_time (us)
0,1           ~100                                     115
2,3           ~90                                        373

It is clear that process time on rpi2,3 is shorter than that on rpi0,1 due
to higher speed CPU. However, I don't understand why worst case on rpi2,3
is much larger than that on rpi0,1. I have repeated this test on both
xenomai 2 and 3, kernel  4.1 and 4.9 (only xenomai 3 in this case) and with
different task priority, the result is quite consistent.
Does anyone have explanation and solution?
Thanks and regards,
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