Re: OT - but am sure you can help me

Bill H wrote:

> Ok guys - put on your thinking caps and see if you can help me here.
>
> I need a simple circuit that will plug into a PC Parallel port (or
> serial) that will sound a buzzer or bell if something is printed out
> the port. The computer that is printing is not hooked up to the printer
> and the program that is dumping the printout does not check if the
> printer is there, so all we need to do is detect that something is
> being printed and turn on the buzzer, then the buzzer turns off when
> the printing is completed.
>
> Bill H www.ts1000.us

Not sure what you are after, if I understand you effectively want a circuit
that makes a noise when some software prints via the parallel port?

>From memory:

Single directional parallel ports basically have a very simple handshake,
when a byte is ready to be read by the printer a signal is generated by the
PC and when the printer has received the byte a signal is pulsed by the
printer.

If you don't intend to have a printer on the end of the circuit you will
need to generate a pseudo pulsing signal to fool the PC into thinking it
has received the data. Then you can either use the PC output handshaking
pin to activate your bell or you could use 1 or all 8 ORed of the data
pins, depending on if you want a single tone or a random noise effect.

You may need to also connect up certain error pins such as paper out etc. to
ensure the PC is happy to print.

If that is what you after I think the circuit would be very simple, a 555
timer for the pulsing would probably be sufficient.

ZX2001

.

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