[fpc-pascal] Parallel Port Access with Free Pascal - windows

Mark Morgan Lloyd markMLl.fpc-pascal at telemetry.co.uk
Fri Jul 22 16:19:20 CEST 2016

James Richters wrote:
> What I need to do is be able to read some 5v TTL Inputs in and write some 5v
> TTL outputs out.  The parallel port always worked when my program was a DOS
> program.. it was so simple, just do Port[$378]:= data to set the bits on the
> port  or data:=port[$378] to read some bits from the port.   I'm not opposed
> to some hardware other than a parallel port if it will be able to interface
> with freepascal easily, if anyone can make a recommendation.   Serial ports
> won't work because they are not made to just read and write bits like the
> parallel port and they are not TTL voltage levels.

Something like a Velleman K8055, which I've talked to using libusb on 
Linux. Or an Arduino with appropriate firmware. Or go the whole hog and 
port the program onto a Raspberry Pi: Bo's doing something like you're 

Any of those have the advantage that the electronics can be positioned 
to minimise the signal run carrying TTL. Long printer cables are 
generally bad news.

Mark Morgan Lloyd
markMLl .AT. telemetry.co .DOT. uk

[Opinions above are the author's, not those of his employers or colleagues]

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