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From: Simon Clubley <clubley@remove_me.eisner.decus.org-Earth.UFP>
Newsgroups: comp.lang.ada
Subject: Re: Cleanest Ada way to do this?
Date: Mon, 23 Jun 2014 11:57:39 +0000 (UTC)
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Date: 2014-06-23T11:57:39+00:00
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On 2014-06-23, rrr.eee.27@gmail.com <rrr.eee.27@gmail.com> wrote:
> On Sunday, June 22, 2014 6:51:01 PM UTC+2, Mike Silva wrote:
>> I'd like some help on the cleanest, or most elegant, way to do this in Ada. I'm writing to an LCD character display, in 4-bit mode, which requires writing an 8 bit character or command value as two 4 bit pieces. The port (a memory address) being written to is 32 bits wide. What I would like to be able to do is some form of this (not valid Ada, I know): Port32(4..7) := Some_Char(4..7); ..twiddle some other control bits.. Port32(4..7) := Some_Char(0..3); ..twiddle some other control bits.. Any thoughts?
>
> You have to drive not only the four data lines but also some Enable or
> RegisterSelect lines (for the standard LCD controller HD44780). Those have to
> be written in parallel. the second nibble (other half of the byte) has to
> follow with specific timing. I recommend a look on lcd.ads, lcd.adb, and
> lcd-wiring.ads from AVR-Ada at
> http://sourceforge.net/p/avr-ada/code/ci/master/tree/avr/lcd/.
>

Dammit. That's something I should have thought to go looking for as well.

I see they are also using Character'Pos for the conversion although they
are also using a more generic approach of treating each data I/O line in
isolation instead of as a related block of 4 contiguous lines.

Simon.

-- 
Simon Clubley, clubley@remove_me.eisner.decus.org-Earth.UFP
Microsoft: Bringing you 1980s technology to a 21st century world