hd44780.docbook

linux下LCD驱动的例子代码

</para>

<para>
If you want to connect more than two displays to the parallel port then
wire D5 (pin 7) to the enable line (pin 6) of the third LCD. Then for
displays four to seven use:
</para>

<table>
<title>HD44780: 4-bit Pinouts (2)</title>
<tgroup cols="2">
  <thead>
    <row>
      <entry>printer port</entry>
      <entry>LCD</entry>
    </row>
  </thead>
  <tbody>
    <row>
      <entry>STR (1)</entry>
      <entry>EN4</entry>
    </row>
    <row>
      <entry>LF (14)</entry>
      <entry>EN5</entry>
    </row>
    <row>
      <entry>INIT (16)</entry>
      <entry>EN6</entry>
    </row>
    <row>
      <entry>SEL (17)</entry>
      <entry>EN7</entry>
    </row>
  </tbody>
</tgroup>
</table>

<para>
The optional keypad can be connected as follows:
</para>

<table>
<title>HD44780: 4-bit Keypad Pinouts</title>
<tgroup cols="2">
  <thead>
    <row>
      <entry>printer port</entry>
      <entry>LCD</entry>
  </row>
  </thead>
  <tbody>
    <row>
      <entry>D0 (2)</entry>
      <entry>Y0</entry>
    </row>
    <row>
      <entry>D1 (3)</entry>
      <entry>Y1</entry>
    </row>
    <row>
      <entry>D2 (4)</entry>
      <entry>Y2</entry>
    </row>
    <row>
      <entry>D3 (5)</entry>
      <entry>Y3</entry>
    </row>
    <row>
      <entry>D4 (6)</entry>
      <entry>Y4</entry>
    </row>
    <row>
      <entry>D5 (7)</entry>
      <entry>Y5</entry>
    </row>
    <row>
      <entry>nSTRB (1)</entry>
      <entry>Y6</entry>
    </row>
    <row>
      <entry>nLF  (14)</entry>
      <entry>Y7</entry>
    </row>
    <row>
      <entry>INIT (16)</entry>
      <entry>Y8</entry>
    </row>
    <row>
      <entry>nSEL (17)</entry>
      <entry>Y9</entry>
    </row>
    <row>
      <entry>nACK (10)</entry>
      <entry>X0</entry>
    </row>
    <row>
      <entry>BUSY (11)</entry>
      <entry>X1</entry>
    </row>
    <row>
      <entry>PAPEREND (12)</entry>
      <entry>X2</entry>
    </row>
    <row>
      <entry>SELIN (13)</entry>
      <entry>X3</entry>
    </row>
    <row>
      <entry>nFAULT (15)</entry>
      <entry>X4</entry>
    </row>
  </tbody>
</tgroup>
</table>

<para>
The optional backlight wiring should be connected to D5, pin 7.
</para>

</sect3>

<sect3 id="hd44780-8-bit-winamp">
<title>8-bit "Winamp"</title>

<para>
This type of connection should work with winamp.
</para>

<table>
<title>HD44780: "Winamp" wiring</title>
<tgroup cols="2">
  <thead>
    <row>
      <entry>printer port</entry>
      <entry>LCD</entry>
    </row>
  </thead>
  <tbody>
    <row>
      <entry>D0 (2)</entry>
      <entry>D0 (7)</entry>
    </row>
    <row>
      <entry>D1 (3)</entry>
      <entry>D1 (8)</entry>
    </row>
    <row>
      <entry>D2 (4)</entry>
      <entry>D2 (9)</entry>
    </row>
    <row>
      <entry>D3 (5)</entry>
      <entry>D3 (10)</entry>
    </row>
    <row>
      <entry>D4 (6)</entry>
      <entry>D4 (11)</entry>
    </row>
    <row>
      <entry>D5 (7)</entry>
      <entry>D5 (12)</entry>
    </row>
    <row>
      <entry>D6 (8)</entry>
      <entry>D6 (13)</entry>
    </row>
    <row>
      <entry>D7 (9)</entry>
      <entry>D7 (14)</entry>
    </row>
    <row>
      <entry>nSTRB (1)</entry>
      <entry>EN (6)</entry>
    </row>
    <row>
      <entry>nLF (14)</entry>
      <entry>nRW (5) (EN3 6 - LCD 3) (optional (*) )</entry>
    </row>
    <row>
      <entry>INIT (16)</entry>
      <entry>RS (4)</entry>
    </row>
    <row>
      <entry>nSEL (17)</entry>
      <entry>EN2 (6 - LCD 2) (optional)</entry>
    </row>
  </tbody>
</tgroup>
</table>

<para>
(*) on the RW line of the display: this line decides whether the display receives data from the 
LPT port, or whether it sends data to the LPT port. If grounded, it receives. If High or connected 
to nothing at all, it "sends" (i.e., will not work as intended). So, if you are not sure that 
you need it otherwise, then connect it to GND. This certainly applies if you have only one display.
</para>

<para>
If you want the display to work with the Winamp plugin, wire nLF (pin 14)
to nRW of your LCD. You can then use the plugin in bidirectional mode (wich
is much faster). With 3 connected LCDs this is not possible.
Note from Benjamin: I haven't tried using winamp while having the third LCD
connected to this line.
</para>

<para>
The optional keypad can be connected as follows:
</para>

<table>
<title>HD44780: "Winamp" wiring - Keypad</title>
<tgroup cols="2">
  <thead>
    <row>
      <entry>printer port</entry>
      <entry>keypad</entry>
    </row>
  </thead>
  <tbody>
    <row>
      <entry>D0 (2)</entry>
      <entry>Y0</entry>
    </row>
    <row>
      <entry>D1 (3)</entry>
      <entry>Y1</entry>
    </row>
    <row>
      <entry>D2 (4)</entry>
      <entry>Y2</entry>
    </row>
    <row>
      <entry>D3 (5)</entry>
      <entry>Y3</entry>
    </row>
    <row>
      <entry>D4 (6)</entry>
      <entry>Y4</entry>
    </row>
    <row>
      <entry>D5 (7)</entry>
      <entry>Y5</entry>
    </row>
    <row>
      <entry>D6 (8)</entry>
      <entry>Y6</entry>
    </row>
    <row>
      <entry>D7 (9)</entry>
      <entry>Y7</entry>
    </row>
    <row>
      <entry>nLF (14)</entry>
      <entry>Y8</entry>
    </row>
    <row>
      <entry>INIT (16)</entry>
      <entry>Y9</entry>
    </row>

    <row>
      <entry>nACK (10)</entry>
      <entry>X0</entry>
    </row>
    <row>
      <entry>BUSY (11)</entry>
      <entry>X1</entry>
    </row>
    <row>
      <entry>PAPEREND (12)</entry>
      <entry>X2</entry>
    </row>
    <row>
      <entry>SELIN (13)</entry>
      <entry>X3</entry>
    </row>
    <row>
      <entry>nFAULT (15)</entry>
      <entry>X4</entry>
    </row>
  </tbody>
</tgroup>
</table>

<para>
The optional backlight wiring should be connected to nSEL, pin 17.
</para>

</sect3>

<sect3 id="hd44780-8-bit-lcdtime">
<title>8-bit "lcdtime"</title>

<para>
This is originally based on "lcdtime" (by Benjamin Tse
<email>[e-mail]</email>) and allows you to combine the LCD with a LED
bargraph. The LCD is driven by LCDproc and the LEDs by another program
such as portato. Further details can be obtained from:
</para>

<para>
<ulink url="http://metalab.unc.edu/pub/linux/system/status/lcdtime-0.2.tar.gz">http://metalab.unc.edu/pub/linux/system/status/lcdtime-0.2.tar.gz</ulink>
<ulink url="http://metalab.unc.edu/pub/linux/system/status/meter-0.2.tar.gz">http://metalab.unc.edu/pub/linux/system/status/meter-0.2.tar.gz</ulink>
<ulink url="http://metalab.unc.edu/pub/linux/system/status/portato-1.2.tar.gz">http://metalab.unc.edu/pub/linux/system/status/portato-1.2.tar.gz</ulink>
</para>

<note>
<para>
Theoretically this wiring sends the data over twice as slow as the
winamp or ext8bit wirings, because it only sends 4 bits at a time.
</para>
</note>

<para>
The LCD connections are:
</para>

<table>
<title>HD44780: "lcdtime" wiring</title>
<tgroup cols="2">
  <thead>
    <row>
      <entry>printer port</entry>
      <entry>LCD</entry>
    </row>
  </thead>
  <tbody>
    <row>
      <entry>D0 (2)</entry>
      <entry>D0 (7)</entry>
    </row>
    <row>
      <entry>D1 (3)</entry>
      <entry>D1 (8)</entry>
    </row>
    <row>
      <entry>D2 (4)</entry>
      <entry>D2 (9)</entry>
    </row>
    <row>
      <entry>D3 (5)</entry>
      <entry>D3 (10)</entry>
    </row>
    <row>
      <entry>D4 (6)</entry>
      <entry>D4 (11)</entry>
    </row>
    <row>
      <entry>D5 (7)</entry>
      <entry>D5 (12)</entry>
    </row>
    <row>
      <entry>D6 (8)</entry>
      <entry>D6 (13)</entry>
    </row>
    <row>
      <entry>D7 (9)</entry>
      <entry>D7 (14)</entry>
    </row>
    <row>
      <entry>nSEL (17)</entry>
      <entry>-</entry>
    </row>
    <row>
      <entry>nSTRB (1)</entry>
      <entry>RS (4)</entry>
    </row>
    <row>
      <entry>nLF (14)</entry>
      <entry>RW (5) (LCD2 - 6) (optional - pull all LCD RW low (*))</entry>
    </row>
    <row>
      <entry>INIT (16)</entry>
      <entry>EN (6)</entry>
    </row>
  </tbody>
</tgroup>
</table>

<para>
(*) on the RW line of the display: this line decides whether the display receives data from the 
LPT port, or whether it sends data to the LPT port. If grounded, it receives. If High or connected 
to nothing at all, it "sends" (i.e., will not work as intended). So, if you are not sure that 
you need it otherwise, then connect it to GND. This certainly applies if you have only one display.
</para>

<para>
See the lcdtime tar-ball (above) for full details of the bargraph
connections.
</para>

<para>
The optional keypad can be connected as follows:
</para>

<table>
<title>HD44780: "lcdtime" wiring - keypad</title>
<tgroup cols="2">
  <thead>
    <row>
      <entry>printer port</entry>
      <entry>keypad</entry>
    </row>
  </thead>
  <tbody>
    <row>
      <entry>D0 (2)</entry>
      <entry>Y0</entry>
    </row>
    <row>
      <entry>D1 (3)</entry>
      <entry>Y1</entry>
    </row>
    <row>
      <entry>D2 (4)</entry>
      <entry>Y2</entry>
    </row>
    <row>
      <entry>D3 (5)</entry>
      <entry>Y3</entry>
    </row>
    <row>
      <entry>D4 (6)</entry>
      <entry>Y4</entry>
    </row>
    <row>
      <entry>D5 (7)</entry>
      <entry>Y5</entry>
    </row>
    <row>
      <entry>D6 (8)</entry>
      <entry>Y6</entry>
    </row>
    <row>
      <entry>D7 (9)</entry>
      <entry>Y7</entry>
    </row>
    <row>
      <entry>nSTRB (1)</entry>
      <entry>Y8</entry>
    </row>
    <row>
      <entry>nSEL (17)</entry>
      <entry>Y9</entry>
    </row>

    <row>
      <entry>nACK (10)</entry>
      <entry>X0</entry>
    </row>
    <row>
      <entry>BUSY (11)</entry>
      <entry>X1</entry>
    </row>
    <row>
      <entry>PAPEREND (12)</entry>
      <entry>X2</entry>
    </row>
    <row>
      <entry>SELIN (13)</entry>
      <entry>X3</entry>
    </row>
    <row>
      <entry>nFAULT (15)</entry>
      <entry>X4</entry>
    </row>
  </tbody>
</tgroup>
</table>

<para>
The backlight wiring should be attached to nSEL, pin 17. Because the portato
program (mentioned above) also uses this pin to control the bargraph, you
cannot use the backlight control together with the bargraph.
</para>

</sect3>

<sect3 id="hd44780-seriallpt">
<title>Serial LPT</title>

<para>
This interface uses a handful of wires to interface to the
HD44780. Suitable for high noise, long connections. Designed by
Andrew McMeikan <email>[e-mail]</email>. The original wiring and
driver can be found at:
</para>
<para>
<ulink url="http://members.xoom.com/andrewmuck">http://members.xoom.com/andrewmuck</ulink>
</para>

<para>
I (Joris) have extended this driver and the wiring a bit. It now supports
keys again (it had earlier supported keys, but some time did not).
</para>

<para>
Further I have extended the driver and the wiring to be able to run