--- Tim Waugh <twaugh@redhat.com> wrote:
> On Thu, Jan 09, 2003 at 04:48:03PM -0800, Calle Be wrote:
>
> >
> > Hi there Joe,
> >
> > Many thanx for your answer. Tim's and mine mail volley continued outside of
> the
> > mailing list and finally he answered the following:
> >
> > echo -ne \\377 | dd of=/dev/port bs=1 seek=$((3*256+7*16+8))
> >
> > which I couldn't really follow until your reply. Well, I _still_ doesn't
> really
> > follow Tim's line but now it seems I've got myself a better way. Your
> >
> > echo -e "\577\c" > /dev/lp0
>
> That does a printer handshake (strobe, ack, etc) as well though, which
> I didn't think you wanted?
>
> Tim.
Well, I want the strobe but not to have to send anything back to the port from
my device. Here's what the LED display driver information says:
'Data can be written by setting up a 3 bit binary code on the digit address
inputs and applying a low level to the WRITE pin.'
The timing diagram is something like this:
Address ---\/-----------------------\/-------
bits ---/\-----------------------/\-------
WRITE ---------\ ------------
pin --------------/
Data ---------------\/---------------\/---
---------------/\---------------/\---
1. Set the 3 address pins and hold them.
2. Set WRITE pin low.
3. Set the 4 data pins and hold then.
4. Set WRITE pin high.
5. Now I can't change anything (or so I think)
Since it's 4 data bits, 3 address bits and one WRITE bit needed, I guess I
_could_ manage without the printer handshake. Is it the
echo -ne \\377 | dd of=/dev/port bs=1 seek=$((3*256+7*16+8))
line I want then? What does the double backslash do? And could you explain the
seek option a bit more? I've read the man page but don't get that part.
/Calle Be
P.S. The data sheet for my LED driver can be found at
http://www.elfa.se/pdf/73/737/07376049.pdf . I'm gonna use the C/D version.
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This archive was generated by hypermail 2b29 : Fri Jan 10 2003 - 08:49:31 EST