[Noisebridge-discuss] First e-mail, and an LCD question

[d p chang]

Michael Frederickson <michael.frederickson at gmail.com> writes:

> Specifically, my current project includes trying to get some info
> displaying on an HD44780 LCD with a PIC16F690 microcontroller, using
> some code I'm trying to compile with HI-TECH's compiler. 
> I'm having a bit of trouble, and think it's probably in my
> timing.

i think you'd have a hard time signalling faster than the minimum
setup/hold times on the lines w/ a pic. eg, in pseudocode a write could
look like

      rs   = <whatever>
      rw   = 0
  <setup>
      en   = 1
      data = <whatever>
  <setup>
      en   = 0
  <hold>
      rs   = Z
      rw   = Z
      data = Z

w/o checking for exact #s, setup/hold are in the tens of ns range (at
least < 100ns). any delay here would be enough to meet the timing
constraints easily (given something like the 8mhz internal clock).

thinking about this a little more, you can't release/toggle en too
soon/fast (on the order of a few cycles should be enoug), but i don't
think that the lcd refreshes that fast either :-)

\p
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