Help Testing LPT Port

[Scott Slater]

I am writing a program that uses a Cash Drawer attached to an LPT port
and am wondering is there any way to test the LPT port to see if it
is ready before writing to it. I am opening the port with the OPEN
statement as follows;

Open "LPT1:" For Output As 1
Print# 1, "Hello"
Close 1

In the above code if the device on LPT1 were not turned on, the program
hangs on the PRINT# 1, "Hello" line forever. Does anyone know how to
check the status before sending to the Port? Thanks in advance!


Scott Slater


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[Gregery D Engle]

Scott,

I know Lance would know more about this then I would. But using
the open "LPT1:" etc is not a reliable method. I would recommend
getting a driver to communicate to the LPT port directly. I
don't know of a website off the top of my head but maybe someone
else has a website? Lance?

Hope that helps.

------------------
-Greg

[Peter Lameijn]

http://www.lvr.com/

------------------
Peter.
mailto[email protected][email protected]</A>

[Gregery D Engle]

Yep that's the site

------------------
-Greg

[Scott Slater]

I was looking for maybe a small ASM routine or a Windows API Call
that would show me the status of a port. I only need to send 3
characters to the port so I didn't want to use a driver. I tried
going through the "Generic / Text Only" Printer Driver, but it filters
out escape sequenses...


Scott

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[Gregery D Engle]

Ring3 applications can't access ports directly with in NT. You
will need a driver for this. You can output directory with
ports in the Win9x kernal. With OUT and IN asm opcodes.

Here is something that will work for direct access to ports:

SUB pbOut(BYVAL iPORT AS INTEGER, BYVAL value AS INTEGER)
    #REGISTER NONE
    ! mov AX, value
    ! mov DX, iport
    ! out DX, AL
END SUB

FUNCTION pbInp(BYVAL iPORT AS INTEGER) AS INTEGER
    #REGISTER NONE
    ! mov DX, iport
    ! in AL, DX
    ! mov FUNCTION[0], AL
END FUNCTION

------------------
-Greg

[Scott Slater]

I just tried PBINP and it works great! Thanks. I just checked to
see if it was running under NT or not before making the call. Under
NT the OS will spool the job in a print queue if the device is not
online. So it works on both platforms. Thanks again...


Scott


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[Lance Edmonds]

The details of using !IN and !OUT along with the link to the LVR site are in the FAQ forum.

However, as you found, you can open the port directly with OPEN "LPT1" FOR OUTPUT AS #1 - the key here is to *omit* the colon from "LPT1:". However, since windows does not signal an off-line state, the code that sends data will block until the port becomes "ready".

Therefore, using an I/O driver is a more effective solution.

------------------
Lance
PowerBASIC Support
mailto:[email protected][email protected]</A>