Re: [PARPORT] simulating a printer

Andrea Arcangeli (
Sat, 10 Oct 1998 15:06:40 +0200 (CEST)

On Sat, 10 Oct 1998, David Campbell wrote:

>Short both BUSY and PAPER OUT the print job dissappears from the queue.

Yes. Doing so you tell to lp "hey lp, are you so slow, I am just ready!"

>Andrea, I think we now have some means of testing printer driver speed
>(without testing the printer speed :-)

;->. The point is that printer are slower and lp could overload the
machine if tuned with a short cut in the parallel port. For example for be
maxmal efficient I need to set tunelp -c 1 that means that my lp will go
to sleep the first time it finds the printer BUSY when attempt to send the
next char. And more important you can' t be able to tune LP_WAIT_TIME...

>This proves that the strobe pulse sent by the computer to the printer has the
>correct polarity such that when fed back in the ACK pin it will cause and
>interrupt for every STROBE pulse. The STROBE pulse is often short,
>therefore it is unlikely that a polling driver (kernel or user space) would notice
>the pulse without the aid of interrupts.


>AFAIK this is impossible from a user space driver. Perhaps we need an


>ioctl() to catch IRQ pulses where a bit is set when an IRQ occurs the ioctl()
>returns the state of the bit and clears the latch.


>Suggested wiring:
>src dir dest name
>1 out 10 STROBE to ACK
>2 out 2 D0
>3 out 3 D1
>4 out 4 D2
>5 out 5 D3
>6 out 6 D4
>7 out 7 D5
>8 out 8 D6
>9 out 9 D7
>10 in 1 ACK to STROBE
>11 in 15 BUSY to FAULT
>12 in 16 PAPEROUT to INIT
>13 in 17 SELECT to SELECT
>14 out ?? AUTOLF (do we care?)
>15 in 11 FAULT to BUSY
>16 out 12 INIT to PAPEROUT
>17 out 13 SELECT to SELECT
>18 to 25 are ground returns
>Comments anyone??

I agree with you ;-).

Andrea Arcangeli

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