LPT port

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21 Aug 2021 19:35 #218341 by rider-83
LPT port was created by rider-83
I currently have an arrangement were a relay controls the power supply to a device, and the said relay is controlled via the LPT port. The relay is in a 'normally open' state therefor no power reaches the device until the relay is switched 'true' as requiredAs the PC powers up, part of the boot procedure is to send the LPT pins true. This momentarily switches on the relay until the system has finished the boot up. This is not a desirable condition.
Any ideas how I can keep this relay from switching until the system boots up ?

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21 Aug 2021 20:23 #218344 by tommylight
Replied by tommylight on topic LPT port
Change the pin used, not all pins go high during boot.
Or use a "charge pump", can be "easily" made with a transistor, a resistor and a capacitor.
Also add on parallel to PCI or PCI-E cards do not output diagnostic data, hence do not switch outputs during boot.

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22 Aug 2021 07:07 #218381 by rider-83
Replied by rider-83 on topic LPT port
Thank you :)

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22 Aug 2021 09:39 - 22 Aug 2021 09:57 #218389 by rider-83
Replied by rider-83 on topic LPT port
I'm having a little trouble with syntax.
I want to use 'xenable joint.0.amp-enable-out' to send LPT pin 4 high when the F2 button (power on) is pressed.

This is what I have tried:
net xenable joint.0.amp-enable-out => stepgen.0.enable
net xenable joint.0.amp-enable-out => parport.0.pin-4-out
setp parport.0.pin-4-out-reset 1

And:
net xenable joint.0.amp-enable-out => stepgen.0.enableĀ => parport.0.pin-4-out
setp parport.0.pin-4-out-reset 1


But HAL gives me the error: 'parport.0.pin-4-out' does not exist
Last edit: 22 Aug 2021 09:57 by rider-83.

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22 Aug 2021 10:13 #218396 by rider-83
Replied by rider-83 on topic LPT port
Sorry, I've worked it out :)
All good
The following user(s) said Thank You: tommylight

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22 Aug 2021 10:25 #218398 by tommylight
Replied by tommylight on topic LPT port
Nice.

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22 Aug 2021 14:21 #218412 by rider-83
Replied by rider-83 on topic LPT port
I moved the connection from the system LPT port to a PCI LPT add on port, but that goes high also.

Looks like it will have to be a 'charge pump' .
Are there any example of how I assemble one of these ?

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26 Aug 2021 22:05 #218830 by andypugh
Replied by andypugh on topic LPT port
Have you checked all the pins on the port?

Pin 1, IIRC is hardware inverted, so I wouldn't expect that to go high. But it might well start high then go low....

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14 Sep 2021 18:02 #220635 by rider-83
Replied by rider-83 on topic LPT port
Hey Andy,

Sorry for the lack of response, I've been out the country.
So I tried pin1 on Lpt 0 and that worked fine. No need for charge pump.
Thanks.
Next thing for me to catch up on is that missing tooth issue on my other thread. That will be later.
Thanks for you help

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