Hi,

On  8 Mar 99 at 16:59, John Payson wrote:
> |            Has anybody written any RS232 code in Qbasic for the Parallel
> |port. I have written I2C and SPI without any trouble but RS232 eludes me I
> |even used a machine independant delay routine based on the Hardware of the
> |computer but without much success, sometimes it seems to work but not quite
> |right. Any input would be welcome. And before you go writing it I know I
> |have several perfectly good serial ports, but HEY!! some things just have to
> |be done just because they can be.

I've written code for half-duplex RS232 comm. through the parallel
port (fixed speed, 9600bps) in C, it ran fine on 8088 XT's so the
horsepower is in there.  As far as I remember I've used the tone
generator timer to avoid messing with the time keeping.  This was for
transmitting.  I used a calibrated software delay for receiving.
The application was mainly transmitting and just receiving a few
chars at a known time.

 You need to disable the timer interrupt while receiving/transmitting
or it might kick in and upset your timing in the middle of the byte.
I'm not sure Qbasic is the right tool for the job...  What speeds are
you aiming at?

Let me know if you want me to look up my old C code for you... My
old Sincalir ZX-Spectrum used to have software RS232 communications
(half-duplex but variable speed), Z80 assembly.

Hope this helps,
Guy