I was in windoze when your last email came in, so I can't reproduce it here.
My idea of a generalised process control system could be summarised as follow:
RTL KERNEL
IO drivers
. serial, ex: OPTOMUX
. parallel, ex: PAMUX
. custom, ex: DH+
. Also need TCP/IP through user space!
KCL Kernel Control Logic
. PID
. Motor Control
. Ladder Logic
. Coffee Machine or Whatever...
USER SPACE
Operator Interface
. Process Control Screens (dynamically linked visual representation)
. Analog Data Trending Module
. Alarm Historical Display Module
Statistical Analysis
Reporting
Anybody will agree this is a reasonable structure. The problem is that more and
more industrial control PLC's support
TCP/IP. Even OPTO 22 does now. Also the Operator Interface should run over the
network. So, efficient RTL-US ipc
seems to be a must for good OI bandwith and TCP/IP access. I hacked an ETHERNET
NIC driver last summer to be able to bridge out of QNX 2. I sure as hell don't
want to do that again for all the network boards out there...
Concerning using cli() and sti() in user space, I read somewhere it kills SMP.
And SMP is a nice thing to have although
450 MHz PENTIUMS will sit idle for most applications.
Regards
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