piclist 2001\03\29\164534a >
Thread: PICs and LCDs - Open Drain?
face BY : mike@EraseMEwhitewing.co.uk

On Thu, 29 Mar 2001 14:51:00 +0100, you wrote:

>Hi All,
>Please correct me if I'm wrong anywhere here...don't want another duff
>circuit board.
>>From my understanding of LCDs, you have to switch the polarity several times
>a second in order for them to work. .well not in order for them to work, but in order for them to live for
a sensible amount of time. They will work on DC, but not for long!
>So, BP goes negative, and segments which
>you want on go positive, the rest go negative...then the BP goes positive,
>segments which you want on go negative, and the rest go positive. Is that
Yes. It is important that the dudty cycle is EXACTLY 50%, so the best
software is to 'flip' everything at a constant interval. If segments
are on more than one port you may have problems getting simultaneous
>Finally, what is an open drain type output. Is this type of output still
>safe to use on LCDs?
No - you'd need pullups, which would draw power, and there is a high
risk of asymmetrical drive, which can effectively act as a DC bias,
reducing life.
>Chris Pringle
>Administrator of "The Linux Site"

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<hsr6ct8gdvs0jhm43opkkg8jgr2hddgp9r@4ax.com> quoted-printable

In reply to: <AMEHJBHHNOBFHNJMBKMFIEIMDFAA.cpringle@latrigg.demon.co.uk>
See also: www.piclist.com/techref/io/lcd/pic.htm?key=lcd
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Subject (change) PICs and LCDs - Open Drain?

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