Re: Why I get random task period ?

What result do you get by checking the RTAI installation with both the user/krnel latency tests?
Paolo.
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From: Rtai [[email protected]] on behalf of NULL [[email protected]]
Sent: Tuesday, August 1, 2017 9:03 AM
To: rtai
Subject: [Rtai] Why I get random task period ?

Hello everybody:
        I start my RTAI task in kernel space with EtherCAT stack running on it and it seems work well.
        But then I found that the task period is not what I set by using start_rt_timer(), the period is stable but different every time I start it.

        Then I use apic_read(APIC_TMICT) to get the Initial Count Register value and found it is a random number, I support Linux changed it.

        Finally I put apic_write(APIC_TMICT, 3100) in the task function and then I get a stable 1kHz working frequency. As I am using EtherCAT to control an I/O device, the actual frequency can be easily tested by oscilloscope.
        Although this problem seems solved, I still want to ask:   What is the problem caused by? How can I solve it?  I concern that changing APIC register directly may influence other time related function because they don't know I changed it privately.
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