Re: Parallel port hardware


"JosephKK" <joseph_barrett@xxxxxxxxxxxxx> schreef in bericht
news:xRrOi.5167$4V6.4220@xxxxxxxxxxxxxxxxxxxxxxxxxxxxx
petrus bitbyter pieterkraltlaatditweg@xxxxxxxxxxxxxxxxx posted to
sci.electronics.design:


"Jon Slaughter" <Jon_Slaughter@xxxxxxxxxxx> schreef in bericht
news:A7CNi.412$sm6.247@xxxxxxxxxxxxxxxxxxxxxxx

Placed a printerport schematic on ABSE.

Also see you point for communicating with PGDx. You will need to
keep the printer control line high as long as the PGDx can go into
outputmode. If not you can get a collission and too high a current
in the circuit. That old 7406 could sink a lot of current but one
cannot know about the modern integrated printerports. Guess you do
not know about the PGDx either. (Guess it's not open collector as
you would not have a problem if it was.) So you will need that
serial resistor for current limiting. Ever saw some type of
electronic collission detection but it is too late to look after
it now.

petrus bitbyter




You will need to limit the current somehow because sometimes both
outputs will happen happen to be active at the same time


Yes, this is the main problem. Sure I can program it so its high
through the programming but I'd rather not take that chance in
general. I'm not quite sure how to handle this. The problem is with
the pic though. I could add a resistor to limit the current but
then it will reduce the voltage. Although it might not matter to
much.

I send an schematic to alt.binaries that shows the idea I'm looking
at.

Thanks,
Jon.


Did not find the collission detection but I think the circuit below
will prevent any output to be blown providing the level shift you
need at the same time.

----+-------+-----+--5V
| | | --+---+--2.5V
.-. .-. | | |
| | 10k| | | .-. .-.
| | | | | | | | |
'-'4k7 '-' | 10k| | | |56k
| | | '-' '-'
| | |\| | |
| +---|-\ ___ | | PIC
SPP | | | |-----|___|--+--)---+------
----+-+-----)---|+/ 2k7 | | I/O
control| | |/| | |
| | LM339 | |
| | | | |
| | | /| | |
| | | /+|--+ |
+-----)-----)-------| | |
| | \-|-----+
| | \| |
| | LM339 |
.-. | .-.
| | | | |
10k| | | 10k| |
'-' | '-'
| | |
| | |
------------+-----+----------------+---------
GND
created by Andy´s ASCII-Circuit v1.24.140803 Beta www.tech-chat.de

Any PIC I/O pin I am aware of can sink and source at least 1mA. So
the 2k7 resistor being the maximum load will prevent damage from I/O
current. At the same time, the input leakage current on a PIC input
pin is in the uA range. So the 56K will prevent the input to become
floating when the output goes tri-state. Some PICs can activate weak
pull ups to do the same.

petrus bitbyter

Tends to get stuck at "0" doesn't it?


You're right, this circuit will not work. I'll have a second look tomorrow
(if I find some time)

petrus bitbyter


.

Relevant Pages

  • Re: Parallel port hardware
    ... Also see you point for communicating with PGDx. ... to keep the printer control line high as long as the PGDx can ... Did not find the collission detection but I think the circuit ...
    (sci.electronics.design)
  • Re: Parallel port hardware
    ... Also see you point for communicating with PGDx. ... keep the printer control line high as long as the PGDx can go into ... Did not find the collission detection but I think the circuit below ...
    (sci.electronics.design)
  • Re: Parallel port hardware
    ... petrus bitbyter pieterkraltlaatditweg@xxxxxxxxxxxxxxxxx posted to ... Also see you point for communicating with PGDx. ... keep the printer control line high as long as the PGDx can go into ... serial resistor for current limiting. ...
    (sci.electronics.design)
  • Re: Parallel port hardware
    ... Also see you point for communicating with PGDx. ... printer control line high as long as the PGDx can go into outputmode. ... So you will need that serial resistor for current limiting. ... Did not find the collission detection but I think the circuit below will ...
    (sci.electronics.design)
  • Re: Parallel port hardware
    ... petrus bitbyter pieterkraltlaatditweg@xxxxxxxxxxxxxxxxx posted to ... Also see you point for communicating with PGDx. ... to keep the printer control line high as long as the PGDx can ... Did not find the collission detection but I think the circuit ...
    (sci.electronics.design)