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lcdproc/docs/hd44780_howto.txt
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robijn b3e1506ffa HD44780 update: 
- howto updated
- input pin readout reversed
- 4bit and serialLpt init timing modified
2002-02-22 01:13:24 +00:00

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HD44780 HOWTO
-------------
There are several ways of wiring up the HD44780 devices. Your choice
will probably be governed largely by your ability to wire up each one
and/or a desire to use the device with other programs.
The LCDproc HD44780 driver supports the following connections on a
parallel port:
- 4-bit
- 8-bit (winamp style)
- extended 8-bit (LCD + LED bargraph)
- serial LPT
And supports a PIC-an-LCD connected to a serial port.
The driver also lets you use multiple displays as a single virtual
display. For example, a 4, 2 and 1 line display can be used to form a
7 line display. The number of displays is limited by the individual
HD44780 driver.
1. Connections
--------------
1.1 Common connections for all connectiontypes
-----------------------------------------------
No matter what connectiontype you choose, you will always need some
connections. They are explaned here.
1.1.1 Power
------------
All variants use the same method of obtaining power. i.e., for each LCD:
LCD pin signal
1 GND (connect to any of pins 18 - 25 of you parallel port)
2 +5V
3 Vadj (contrast)
WARNING: Always double check your power connection, your display probably
wont survive a reversely connected supply !
There are several ways to get 5V:
- Connect to a 5V line intented for disk drives (the red wire is 5V, black
is GND).
- Get it from a joystick port (pin 1 and 9 are 5V, 4, 5 and 12 are GND).
It seems that some soundcards can use these lines for communication, so
if you want to use this first check wether it really gives a 'clean' 5V.
- If you don't have a backlight, you can sometimes get the needed mA's from
the LPT port itself. Connect a few diodes from the data pins to a
capacitor and you have the 5V. If it's strong enough is another question...
- Get it from the keyboard connector. I do not recommend to use this with a
backlight, as the keyboard connector is often protected with a fuse of
100mA or 200mA.
Connecting the contrast adjusting pin (Vadj.):
(variable resistor)
.------.
Vcc ---| 10k |--- GND
`---^--'
/|\
|
Vadj.
1.1.2 Keypad
-------------
You can connect a keypad with all connection types. The maximum supported
number of keys differs per type. There are several ways to connect the keys
to the input pins.
1.1.2.1 Direct keys
--------------------
If you connect a key like sketched below, then you can only connect one key
per input pin. It is a simple solution if you need only few keys.
O 5V
|
|
-
| | 10k
| |
-
|
+-----------o input (X)
|
|
o
\
o
|
|
=== GND
By default, the following keystrokes are generated by the different keys:
X0 A
X1 B
X2 C
X3 D
X4 E
You should modify and recompile the driver to get other keystrokes.
1.1.2.2 Matrix keys
--------------------
Using a matrix, we can connect much more keys. To simplify the drawing here,
we replace all switches with an @ symbol:
X line
|
|
Y line ---+---------
| | |
o | = --@--
\ | |
o |
| |
+---+
|
|
We connect the matrix of keys like this:
Y0 o---|<---@--@--@
| | |
Y1 o---|<---@--@--@
| | |
Y2 o---|<---@--@--@
| | |
Y3 o---|<---@--@--@ O 5V
| | | |
diodes | | | ___ |
1N4148 +----------|___|---+
| | | ___ |
| +-------|___|---+
| | | ___ |
| | +----|___|---+ resistors 22k
| | |
o o o
X0 X1 X2
As you can see, you need 1 resistor per X line, and 1 diode per Y line.
Lcdproc will presume that you have a keypad with a layout like a telephone
connected, with X and Y lines connected as show. To be more precise, it
assumes this:
X0 X1 X2 X3
Y0 1 2 3 A
Y1 4 5 6 B
Y2 7 8 9 C
Y3 * 0 # D
If you only need 10 keys, leave the rest away. However, the lcdproc menu is
controlled by the keystrokes A to D. You should modify and recompile the
driver to get an other keypad layout.
You can buy arrays of keys that are connected like this in the electronics
shop. They usually call it a matrix keypad. To hook it to lcdproc, you
would only need to add the resistors and diodes.
If you want to use just one return line, for example with the serialLpt
wiring, it looks (completely drawn) like this:
O 5V
|
.-.
| | 4k7 or 22k
diodes | |
1N4148 '-'
___ |
Y0 o---|<---o o---+
___ |
Y1 o---|<---o o---+
___ |
Y2 o---|<---o o---+
___ |
Y3 o---|<---o o---+----o return line
If the driver generates keypresses without that you actually press a key,
it might be that the unconnected input lines are picking up
electromagnetic waves from the air. In that case connect the unconnected
input lines (pin 10, 11, 12, 13 and 15 of the LPT) to VCC = 5V.
1.1.3 Backlight
---------------
A small extension allows you to switch the backlight of the display on
and off. At the moment only the 4bit and winamp connection types support
this. The extension uses one output pin, you cannot use that pin for other
functions anymore. The wiring looks like this:
O 5V
___ |
+---|___|---+
LPT Sub-D connector | 4k7 |
| |e
___ | b |/
BL pin o------------|___|---+---------|
1k |\
bc327 |c
| LCD connector
|
+--------o 15 backlight
+--------o 16 GND backlight
|
=== GND
Note: 4k7 means 4,7 kohm.
The BC327 transistor has the following connections:
_____
| |
|bc327|
|_____|
| | |
| | |
| | |
c b e
Sometimes the backlight connections are not on the 'main' connector, but on
the side. If that is the case, there is usually NO RESISTOR present to limit
the current through the LEDs. Therefor you should then add a resistor after
the transistor of about 10 ohm (see display documentation).
If you want the backlight to light a bit while it's switched 'off', you can
add a resistor bypassing the transistor from e to c, with a value of, say
47ohm or 22ohm. (My 4x20 has an internal resistor of 6ohm, so with 47 ohm
extra it lights at only 1/9th. I like this. Joris.)
1.2 4-bit
----------
This is originally based on "lcdtext" (by Matthias Prinke).
The pinouts are:
printer port LCD
D0 (2) D4 (11)
D1 (3) D5 (12)
D2 (4) D6 (13)
D3 (5) D7 (14)
D4 (6) RS (4)
D5 (7) RW (5) (LCD3 - 6) (optional - pull all LCD RW low)
D6 (8) EN (6)
D7 (9) EN2 (LCD2 - 6) (optional)
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:
printer port LCD
STR (1) EN4
LF (14) EN5
INIT (16) EN6
SEL (17) EN7
The optional keypad can be connected as follows:
printer port keypad
D0 (2) Y0
D1 (3) Y1
D2 (4) Y2
D3 (5) Y3
D4 (6) Y4
D5 (7) Y5
nSTRB (1) Y6
nLF (14) Y7
INIT (16) Y8
nSEL (17) Y9
nACK (10) X0
BUSY (11) X1
PAPEREND (12) X2
SELIN (13) X3
nFAULT (15) X4
The optional backlight wiring should be connected to D5, pin 7.
1.3 8-bit "Winamp"
-------------------
This type of connection should work with winamp.
printer port LCD
D0 (2) D0 (7)
D1 (3) D1 (8)
D2 (4) D2 (9)
D3 (5) D3 (10)
D4 (6) D4 (11)
D5 (7) D5 (12)
D6 (8) D6 (13)
D7 (9) D7 (14)
nSTRB (1) EN (6)
nLF (14) nRW (5) (EN3 6 - LCD 3) (optional)
INIT (16) RS (4)
nSEL (17) EN2 (6 - LCD 2) (optional)
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.
The optional keypad can be connected as follows:
printer port keypad
D0 (2) Y0
D1 (3) Y1
D2 (4) Y2
D3 (5) Y3
D4 (6) Y4
D5 (7) Y5
D6 (8) Y6
D7 (9) Y7
nLF (14) Y8
INIT (16) Y9
nACK (10) X0
BUSY (11) X1
PAPEREND (12) X2
SELIN (13) X3
nFAULT (15) X4
The optional backlight wiring should be connected to nSEL, pin 17.
1.4 Extended 8-bit "lcdtime"
-----------------------------
This is originally based on "lcdtime" (by Benjamin Tse
<blt@ComPorts.com>) 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:
http://metalab.unc.edu/pub/linux/system/status/lcdtime-0.2.tar.gz
http://metalab.unc.edu/pub/linux/system/status/meter-0.2.tar.gz
http://metalab.unc.edu/pub/linux/system/status/portato-1.2.tar.gz
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.
The LCD connections are:
printer port LCD
D0 (2) D0 (7)
D1 (3) D1 (8)
D2 (4) D2 (9)
D3 (5) D3 (10)
D4 (6) D4 (11)
D5 (7) D5 (12)
D6 (8) D6 (13)
D7 (9) D7 (14)
nSEL (17) -
nSTRB (1) RS (4)
nLF (14) RW (5) (LCD2 - 6) (optional - pull all LCD RW low)
INIT (16) EN (6)
See the lcdtime tar-ball (above) for full details of the bargraph
connections.
The optional keypad can be connected as follows:
printer port keypad
D0 (2) Y0
D1 (3) Y1
D2 (4) Y2
D3 (5) Y3
D4 (6) Y4
D5 (7) Y5
D6 (8) Y6
D7 (9) Y7
nSTRB (1) Y8
nSEL (17) Y9
nACK (10) X0
BUSY (11) X1
PAPEREND (12) X2
SELIN (13) X3
nFAULT (15) X4
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.
1.5 Serial LPT
---------------
This interface uses a handful of wires to interface to the
HD44780. Suitable for high noise, long connections. Designed by
Andrew McMeikan <andrewm@engineer.com>. The original wiring and
driver can be found at:
http://members.xoom.com/andrewmuck
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).
Further I have extended the driver and the wiring to be able to run
using 2 instead of 3 output pins. That's even one less pin ! :)
Of course the use of fewer lines than the other wirings can not stay
without drawbacks. In this case the simplicity of the long feeding wires
is compensated by some intelligence in the decoding of the data. If you
have no experience with the soldering iron, I do not recommend to build
this wiring.
OK, so here is the wiring. First of the 'simple' 3 wires version. IC1 is
the shift register, a 4094. Do not forget to connect the 5V to pin 16 and
GND to pin 8 of the IC.
IC1
-----------
| 4094 |
5V | shift reg | display
O | | /keys
| 1| |3
+----|STR Q0|---------------------o 7 D0
| | |4 /Y0
Data | 2| Q1|---------------------o 8 D1
D3 5 o---------------------------|D |5 /Y1
| | Q2|---------------------o 9 D2
| 3|CK |6 /Y2
D4 6 o---------------------------| Q3|---------------------o 10 D3
| | |10 /Y3
| 15| Q4|---------------------o Y4
+----|OE |11
| Q5|---------------------o 4 RS
| |12 /Y5
| Q6|---------------------o Y6
| |13
| Q7|---------------------o Y7
| |9
| QS|-- +--o 5 RW
| __|10 |
| QS|-- ===
| |
-----------
D2 4 o-------------------------------------------------------------o 6 EN
D7 9 o-------------------------------------------------------------o 6 EN2
(2nd LCD)
5V O-----+--------+----------------------------------+-----o 2 VCC
| | |
| | |
|100n O 16 .-.
--- IC1 | |<---o 3 Vlcd
--- O 8 | |10k
| | '-'
GND | | |
18..25 o-----------+--------+--------------------------+-------+-----o 1 GND
|
=== GND
The second possible wiring is with 2 output lines. This one is a bit more
complex. If you do not understand the schematic, do not build it.
IC2
-----------
| 74HCT164 |
| shift reg | display
| | /keys
Data 1| |3
D3 5 o-----------------------+---|D Q0|---------------------o 7 D0
| | |4 /Y0
| 2| Q1|---------------------o 8 D1
+---|D |5 /Y1
| Q2|---------------------o 9 D2
| |6 /Y2
| Q3|---------------------o 10 D3
| |10 /Y3
Clock 8| Q4|---------------------o Y4
D4 6 o---------------------------|CK |11
| Q5|---------------------o 4 RS
___ 9|\ 8 9|_ |12 /Y5
+--|___|--+----| >o----|R Q6|---------------------o Y6
| 22k | |/ | |13
| --- IC1 | Q7|---+ +--o 5 RW
| --- | | | 5V |
| |100p ----------- | O ===
| | | |
| === | .-.
| | | |22k
+--------------------------------------+ | |
| '-'
| ___ 11|\ 10 | 5|\ 6
+--|___|--+----| >o-------------------||----+-----| >o---o 6 EN
22k | |/ 22p |/
--- IC1 IC1
---
|22p
| IC1=74HCT14 (6x Schmitt trigger inverter)
===
5V O--+-------+------+------+------------------------+-----o 2 VCC
| | | | 13|\ 12 |
| | | +---| >o- |
|100n O 14 O 14 |/ .-.
--- IC1 IC2 | |<---o 3 Vlcd
--- O 7 O 7 1|\ 2 3|\ 4 | |10k
| | | +--| >o- +--| >o- '-'
GND | | | | |/ | |/ |
18..25 o--------+-------+------+-------+----------+-----+------+-----o 1 GND
|
=== GND
1.6 PIC-an-LCD serial device "picanlcd"
----------------------------------------
The PIC-an-LCD module is also supported. It is not connected to the LPT port
but to a serial port, which saves you from a lot of potential problems.
To use it, specify the device to which you have connected the module in the
config file with the Device= setting. The default is /dev/lcd.
It does not support a keypad nor backlight switching.
1.5.1 Keypad
------------
To understand this part of the serialLpt documentation, you also need to
read the keypad section in this document.
serialLpt wiring supports a keypad. The 3 wires version supports
8 keys, or if you use multiple return lines up to 8 x 5 = 40 lines. The
2 wires version supports 7 keys, or with multiple return lines
7 x 5 = 35 keys.
The return lines are the following:
nACK (10) X0
BUSY (11) X1
PAPEREND (12) X2
SELIN (13) X3
nFAULT (15) X4
On lines longer than, say a meter, you should buffer the return line(s).
If you only have 1 return line, you can buffer it with two remaining
buffers from the 74HCT14:
1|\ 2 13|\ 12 ___
keypad o-----| >o------| >o---|___|---+---o input pin on LPT port
return |/ |/ 220E |
IC1 IC1 ---
--- 1nF
|
===
Also a backlight is suported. You will also need a port from the 74HCT14 for
that. The BL output below should be connected to the BL input in paragraph
1.1.3.
___ 3|\ 4
Data o-----|___|--+----| >o----o BL output
LPT-D3 470k | |/
--- IC1
---
|100nF
|
===
2. Compiling
------------
Make sure that the HD44780 files are built when you run configure. This
can be done by specifying "--enable-drivers=all" or by
"--enable-drivers=hd44780".
3. Running
----------
Modify the LCDd.conf file before you run LCDd. In this config file are
detailed instructions on how to configure the HD44780 driver.
Then as usual, start LCDd with the correct config file:
LCDd -c ./LCDd.conf
for example.
If you want to override the driver selection in LCDd.conf then use:
LCDd -c ./LCDd.conf -d HD44780
If you use this, the HD44780 driver will read the options from the config
file.
4. Miscellania
---------------
This text originally taken from a message by Bill Farrow
<bfarrow@arrow.bsee.swin.edu.au>.
Updated February 2000, Benjamin Tse (blt@ComPorts.com)
Updated October 2001, Joris Robijn (joris at robijn.net)
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