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hd44780/ftdi: Fix a bug in ftdi_HD44780_backlight() and add backlight

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switching capability for 4bit mode. Document the different BL line level
and a small switching circuit for it.
This commit is contained in:
mmdolze
2012-01-02 09:22:30 +00:00
parent 6336c6c99e
commit 69a6f74c76
3 changed files with 61 additions and 7 deletions
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docs/lcdproc-user/drivers/hd44780.docbook
+41
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@@ -1872,6 +1872,39 @@ The wiring of the control lines can optionally be reconfigured,
please look at the driver source if you really need that.
</para>
<note><para>
The backlight line is driven high when the backlight is <literal>on</literal>.
Therefore the standard backlight circuit (<xref linkend="hd44780-connections-backlight.circuit"/>)
will not work. Use the following instead.
</para></note>
<figure id="hd44780-ftdi-backlight">
<title>hd44780/ftdi: Backlight Wiring</title>
<screen>
<![CDATA[
O 5V
|
+--------o 15 backlight
+--------o 16 GND backlight
|
small resistor .-.
10 - 47 ohm | |
depending on | |
display '-'
|
|c
___ b |/
BL pin o------------|___|-------------|
4k7 |\
BC547 |e
|
=== GND
]]>
</screen>
</figure>
<para>
Alternatively you can use a single channel FTDI FT245BM USB &lt;-&gt; parallel
FIFO chip and use the display in its 4 bit mode.
@@ -1948,6 +1981,13 @@ FIFO chip and use the display in its 4 bit mode.
<entry>RW</entry>
<entry>5</entry>
</row>
<row>
<entry>D7</entry>
<entry>18</entry>
<entry></entry>
<entry>BL</entry>
<entry>Backlight (optional)</entry>
</row>
</tbody>
</tgroup>
</table>
@@ -1967,6 +2007,7 @@ ftdi_mode=4
ftdi_line_EN=0x10
ftdi_line_RS=0x20
ftdi_line_RW=0x40
ftdi_line_backlight=0x80
]]>
</screen>
</example>