98 lines
4 KiB
Perl
98 lines
4 KiB
Perl
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#define _PAGE_ Rocklatin
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#include "head.t"
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<h1>Rocklatin1</h1>
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Only for developers...
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<h2>Background</h2>
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The Archos player comes in two models. One with old LCD and one with new LCD.
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(Differences can be seen below). You can't find any difference more than the
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LCD, therefor we run the same code on both models. The original software
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contains two different mappings from ASCII-character to hardware-LCD. Because
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some characters doesn't exist in both hardwares all national characters
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are left out in both hardware.
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<p>The old LCD can have 4 software defined characters, and the new LCD can
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have 8 software defined characters.
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<table border=1><tr>
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<td>HW layout of old LCD:<br><img width=272 height=272 src="lcd_old_hw.gif"></td>
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<td>HW layout of new LCD:<br><img width=272 height=272 src="lcd_new_hw.gif"></td>
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</tr></table>
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<h2>What is Rocklatin1</h2>
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Rocklatin1 is based on Winlatin1 (which is identical to Latin1 but some
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extra characters). All characters presented in any HW-LCD (i.e. old LCD)
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is mapped in Rocklatin1 and some extra characters we find good to use.
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<table border=1><tr>
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<td>Rocklatin1 of old LCD:<br><img width=272 height=272 src="lcd_old.gif"></td>
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<td>Rocklatin1 of new LCD:<br><img width=272 height=272 src="lcd_new.gif"></td>
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</tr></table>
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The red characters are characters not defined in the HW-LCD. These characters
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are mapped by the software to a software defined character (0-4/8) whenever
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they are used.
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<h2>But what if...</h2>
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...all software defined characters are taken?<br>
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Well, then a substitute character will be used for that character.
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<table border=1><tr>
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<td>Substitute of old LCD:<br><img width=272 height=272 src="lcd_old_subst.gif"></td>
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<td>Substitute of new LCD:<br><img width=272 height=272 src="lcd_new_subst.gif"></td>
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</tr></table>
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The red characters shows where a substitution is made.
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<p>
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All Rocklatin1 characters between 0x00 and 0x1f are hardcoded to be prioritized.
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That means that if a national character is displayed at LCD and an icon
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(0x18-0x1f) is to be shown, the character with highest Rocklatin1 value will
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be switched to a substitute character.
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<h2>Accessing hardware</h2>
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The Rockbox software can access a HW-LCD-character by doing a lcd_putc(0x100-0x1ff). That would of course make it 100% hardware depended (=not good).
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<p>
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The Rockbox software can also define 23 own patterns, even though hardware only
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allows 4 or 8. The software should of course not try to display more than 4
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or 8 of such characters. This code example shows how to define a pattern:
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<pre>
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{
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unsigned char pattern[]={ 0x0a, 0x00, 0x00, 0x0c,
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0x04, 0x04, 0x0e};
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unsigned char handle;
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handle=lcd_get_locked_pattern();
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lcd_define_pattern(handle, pattern);
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lcd_putc(x, y, handle);
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...
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lcd_unlock_pattern(handle);
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}
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</pre>
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The handle is very likely to be between 0x01 to 0x17, which in software will
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be handled as a prioritized character (even higher than the icons).
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<h2>Some notes</h2>
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<ul>
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<li>Displaying the same rocklatin-mapped-character many times at the LCD
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only occupies one HW-LCD-mapped character.
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<li>If a substitute character is used, the "should-be" character will never
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be shown (no flickering screen) until the character is moved or scrolled.
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<li>Characters already displayed are only substituted if a prioritized
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character is to be displayed.
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<li>The software maps the characters circular in order to minimize the
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likelyhood to remap the same character very often.
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<li>The gifs above is generated with the tool "generate_rocklatin".
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<li>Rocklatin character 0x92 is defined as the "cursor" character.
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<li>Rocklatin character 0x93-0x95 is only used for substitution (a substitute
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character must be a Rocklatin character).
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<li>Implementation and design by Kjell Ericson and Mats Lidell (for questions).
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<li>Rocklatin1 is based on Winlatin1 because the old LCD happened to have 7
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of the Winlatin1-extra characters (no need to remap/remove those).
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<li>If you find any characters identical in old and new HW-LCD that aren't
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mapped (and really are useful) you can tell us.
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</ul>
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#include "foot.t"
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