Path: utzoo!utgpu!jarvis.csri.toronto.edu!rutgers!gatech!psuvax1!psuvm.bitnet!ncsuvm.bitnet!netoprbh
From: NETOPRBH@NCSUVM.BITNET (Brandon Hill)
Newsgroups: comp.sys.cbm
Subject: Re: EasyScript to RS232 Printer??
Message-ID: <797NETOPRBH@NCSUVM>
Date: 21 Jun 89 18:13:28 GMT
References: <990001@hpspdra.HP.COM>
Organization: North Carolina State University - Computing Center
Lines: 33

I just bought a new printer, and as I had the RS232 driver chips in a
box, I decided to interface using good ole device 2.  Luckily, the printer
had a device busy hardware line which easily interfaced to the CTS signal the
computer uses to synchronize data transmission in X-line handshake mode.

After hooking up TXD, CTS, and GND thru the appropriate driver chips, the
printer worked fine at 1200 bd with EasyScript driving it.  Therefore,
it is possible to use EasyScript to drive an RS232 printer.

The problem results from the standard XON-XOFF sequences which the device
driver ignores, as it doesn't expect input from the printer.  The solution
may be to determine if one of the control signals on the printer indicates
a busy condition.  If you can find such a singal, then EasyScript should
function ok.

Another problem arises from driving the same device from Basic using the
RS232 interface.  It seems that the CHROUT routine for device 2 will
return an error indication of 16 in the status byte and exit when CTS
goes low.  This doesn't normally result in a problem except that the
RS232 send buffer is not purged when the printer becomes busy.  Thus
you are at most 256 bytes behind...which is quite annoying, and you have
to write a bunch of null bytes to flush the buffer.

The solution to this problem seems to be to replace parts of the CHROUT
routine for device 2 to wait until the printer becomes ready and then
print the next character.

Of course after writing the code to make the RS232 driver flush the
buffer correctly, my wife decided that we should get Geos...and my
serial user port driver had to be rearranged into a parallel GeoCable
interface...incompatible with any other program except Geos as far as
I can tell, but it does work.
                                                       BlH