Hi,
probably the following questions and thoughts show that I
am everything but an expert in operating systems, but any
hints would be appreciated:
I would like to implement feedback control with a 486/33
and an Avantech PCL-818 at a sampling frequency of about
3-10kHz, but only for short periods. Since the preemption
of running jobs take some time until the RT job is scheduled
-interrupt latency of 220usec for Linux and even 84usec
for RT-Linux [according to the thesis of Barabanov]-, the
introduced time delay does not makes the system inappropriate
for a feedback control. For simple measurement or feedforward
control, however, this might be OK. Thus I am looking for
an alternative solution but without loosing the benefits
of a real OS like Linux with networking and X.
In fact, I had once a MATLAB/Simulink generated real time
application running on a DOS machine at 8kHz, of course
without other processes running. What I am thinking of is
the possibility of dispatching a RT-process which only
releases the CPU after a time period programmed in advance
into the CPU, like CPU_Wait_Until_Preemt, such that:
Start_RT_Process(RT_Process, Sampling_Time, Measurement_Time)
processes the following steps:
check(RT_Process, Sampling_Time)
mask_All_Interrupts_Except_CPU_Wait_Until_Preemt
set(CPU_Wait_Until_Preemt, Measurement_Time)
dispatch(RT_Process, Sampling_Time)
set(CPU_Wait_Until_Preemt, Normal_Time)
unmask_All_Interrupts
If after this steps the machine is still alife, the
OS continues as usual. Maybe thats not possible, but
this is the idea of a simple control engineer without
experience in RT-OS and OS in general.
ciao,
peterw
--
Dr. Peter Wurmsdobler
CETEHOR, 39, av. de l'Observatoire 8, rue Jean Petit
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Ceterum censeo MIRCOSOFTem esse delendam.
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