Hi: I have been using FPC for some time now and think it is a great
system.
I am facing a challenging port of a Borland Pascal 7 program to FPC. It
is about
8000 lines long. While most of it is ordinary and will compile easily it
uses some
features and extensions which I don't know how to handle in FPC.
1) It does direct I/O to port addresses via the Borland Port[xxx] feature.
2) It uses a buffered interrupt driven RS-232 facility to receive and
direct access for transmit.
3) It uses the RS-232 control lines separately to to additional
unrelated I/O while normal serial I/O is in progress.
4) It reads/writes the LPT port.
5) It uses interrupts on the LPT port. About 35K ints/sec are used to
drive stepper motors.
6) it writes to a 48 I/O line card on the ISA bus. (hard to find ISA bus
slots)
7) it uses an excellent multitasking library written by Dieter Pawelczak
from Germany.
This allows execution to be interrupted and other tasks run based on
time scheduling.
A simple example would be to set a port bit in the main program and
then schedule
a task to run say 10 msec later which turns it off. The main
program would run normally
until the 10 msec time limit is reached at which time the main is
suspended briefly while
the scheduled task is run. Of course there are various restrictions
and pitfalls because of
rentrancy issues. But it works well when used properly. The source
code is provided for
this library including a bunch of 16 bit oriented ASM code.
8) To avoid OS intervention on I/O port access Windows98 is used.
I would like to port the program as is, but eventually get a PCI 48 I/O
line card to escape
the ISA bus and also talk USB as well. Getting it to run on later
versions of Windows might
be useful. This program controls a machine on a single purpose computer.
Windows is used
to handle files, networks, and little else. Most of the time only this
program is run. A port to
Linux might be acceptable if that would solve some problems.
Are these insurmountable obstacles?
Thanks
John Youngquist
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