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: 4bit 8bit (winamp style) extended 8bit (LCD + LED bargraph) serial LPT It also supports the following connections: A PIC-an-LCD or LCD serializer connected to a serial port A I2C port expander connected to an I2C 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. No matter what connectiontype you choose, you will always need some connections. They are explaned here. 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) Always double check your power connection, your display will probably not 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.

You can connect a keypad with most connection types. The maximum supported number of keys differs per type. There are several ways to connect the keys to the input pins. 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.

By default, the following keystrokes are generated by the different keys: X0 A X1 B X2 C X3 D X4 E Using a matrix, we can connect much more keys. To simplify the drawing here, we replace all switches with an @ symbol:

We connect the matrix of keys like this:

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 X4 Y0 1 2 3 A E Y1 4 5 6 B F Y2 7 8 9 C G Y3 * 0 # D H 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:

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. 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:

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.) This is originally based on "lcdtext" (by Matthias Prinke). printer port LCD name pin name pin 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) (*) 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. 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 LCD 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. This type of connection should work with winamp. printer port LCD name pin name pin 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) (*) 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. 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. 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: 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 name pin name pin 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 (*) 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. 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. 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: 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.

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.

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 ]]>

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. 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:

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 the backlight section

o----o BL output LPT-D3 470k | |/ --- IC1 --- |100nF | === ]]>

LIS2 from VLSystem () is a full featured USB VFD module with four channel fan controls. This device can be accessed as a serial device with the help of the kernel modules ftdi_sio.ko that map the USB port to a serial port (/dev/ttyUSBx). See for more information on this device. … to be documented … Please address Matteo Pillon for further information. The VDR-Wake module by Frank Jepsen is a serial IO extension module for the famous Linux-based VDR that allows to connect an LCD to it and supports LCDproc. See (German) for more information on VDR-Wakeup. The Pertelian X2040 includes an HD44780 display with enclosure and USB connection. In order to work with LCDproc in Linux you need the usbserial.ko and ftdi_sio.ko kernel modules loaded. The display will then be available on a serial port /dev/ttyUSBx. See the X4020 product page for more information. 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. For more information see the PIC-an-LCD User Manual by Dale Wheat. LCD serializer connection is technically the same as PIC-an-LCD with the same advantages, it uses the serial port making things really simple. Unlike PIC-an-LCD LCD serializer is not a commercial product. it's just a project found digging on the net and freely available. You have all the tools and the code to build it yourself and to customize the behaviour of the device. Some electronic knowledge and familiarity with the soldering iron A PIC16F84 (I used PIC16F84A) or PIC16C54 JDM PIC programmer gputils and picprog installed on your GNU/Linux box First, you need to download the ASM source for your PIC and then make the hex: $ gpasm lcd16f84_custom.asm Now the binary is ready to be flashed to the PIC. Connect the programmer with the PIC installed and issue the following command to see it burning ;-): $ picprog --erase --burn --input lcd16f84.hex --pic /dev/ttyS0 It's time to build the operating circuit, remember this driver uses a baud rate of 9600, so JP2 need to be closed. Now power on the board. You should see OK on the LCD screen. Otherwise double-check all the connections. Change LCDd.conf to include the following statements in the [hd44780] section: ConnectionType=lcdserializer Device=/dev/ttyS0 Finally, start the daemon and relax watching lcdproc running. If want to change the default startup message (OK.), you can edit the asm source and write anything you want. Open the asm source with your preferred editor and look for this: This piece of code sends three characters to the LCD. The first line sets the value of w register (working register, aka accumulator) to 0x4F ('O' in ascii). The second line copies this value to ARG1, then the value is sent to the LCD. The fourth line delays the execution. You don't have to write the ASCII values in your modification, gpasm does the translation for you, so if you want to see Booting... at startup, change the code above to look like this: Refer to burning section in order to compile and reflash the new firmware. The BWCT USB LCD module is also supported. It is not connected to an LPT port but to an USB port, which saves you from a lot of potential problems. To use it, set the connection type in the config file with the ConnectionType= setting to "bwctusb" (without the quotes). It does neither support a keypad nor backlight switching but it supports setting the display's contrast using the "Contrast" configuration parameter as well as specifying which one (of multiple BWCT LCD devices) is wanted using the "SerialNumber" configuration parameter. LCD2USB is a cheap but powerful do-it-yourself interface to connect HD44780 based displays via USB, consisting of easily available parts only. The device supports software adjustable contrast and backlight as well as dual controller displays (required for 4*27 and 4*40). It is based upon Atmel AVR Mega8 CPU with a pure software implementation of the USB protocol for the Atmel AVR microcontroller series. The whole interface incl. the hardware layout is under a GPL like license. This means that you can take these schematics and use it as a basis for your own interface e.g. for a graphic LCD Besides the standard configuration options for hd44780 displays, the lcd2usb connection type supports two additional options: Contrast= to set the display's contrast and Brightness= to set the display's brightness. Both options expect a number in the range from 0 to 1000. The lcd2usb connection type has been written to support displays with one and two HD44780 controllers. Owing to the lack of a 2-controller display, it has only been tested with a 1-controller display. If you happen to have a 2-controller display connected to LCD2USB, please report to the mailing list. In order to make the lcd2usb connection type work with a 2-controller display you may need to set the vSpan= config option accordingly. Although the LCD2USB sports two keys, they are currently not supported by LCDproc. Patches to fix the situation are very welcome. If you have an I2C port available that is supported by your kernel (through /dev/i2c*), you can add a I2C port expander there (PCF8574P in this example).

The Device= configuration setting denotes the device file of your I2C bus (here /dev/i2c-0). You have to load the kernel standard module i2c-dev.ko and the bus driver, but no I2C chip modules (e.g. pcf8574.ko)! The Port= config option contains the I2C address of the I2C port expander (here 0x20, the PCF8574 from the example above, with all address bits set to 0). Bit 8 of the address (normally 0 in I2C addresses) has a special meaning: It tells the driver to treat the device as PCA9554 or similar, a device that needs a 2-byte command, and it will be stripped off the address. Port= value Meaning 0x20…0x27 PCF8574 with A[012]=0…7 0x38…0x3f PCF8574A with A[012]=0…7 0xa0…0xa7 PCA9554 with A[012]=0…7 0xa0…0xa7 PCA9554A with A[012]=0…7 Make sure that the HD44780 files are built when you run ./configure. This can be done by specifying --enable-drivers=all or by including hd44780 in the list of enabled drivers (e.g. --enable-drivers=hd44780). Port= PORT Specify the address of the parallel port the LCD is connected to. Common values for PORT are 0x278, 0x378 and 0x3BC. If not given, the default is 0x378. Device= DEVICE If you are using a serial connection, you must set this parameter to the device your LCD is connected to. For example, if the display is connected to the first serial port, you have to set it to /dev/ttyS0. The default value is /dev/lcd. ConnectionType= 4bit 8bit winamp serialLpt picanlcd lcdserializer los-panel vdr-lcd vdr-wakeup pertelian bwctusb lcd2usb lis2 i2c Select the type of the wiring / display connection. ConnectionType Wiring / Display Type 4bit HD44780 4bit Wiring (default) 8bit HD44780 8bit Wiring ("lcdtime") winamp HD44780 8bit Wiring "winamp" Style serialLpt HD44780 Serial LPT Wiring picanlcd PIC-an-LCD serial device "picanlcd" lcdserializer LCD serializer "lcdserializer" los-panel LCD on Serial panel device "los-panel" () vdr-lcd VDR LCD serial device "vdr-lcd" vdr-wakeup VDR-Wakeup module "vdr-wakeup" pertelian Pertelian X2040 LCD display () bwctusb BWCT USB device "bwctusb" () lcd2usb Tim Harbaum's LCD2USB () lis2 LIS2 from VLSystem () i2c LCD driven by PCF8574(A)/PCA9554(A) connected via I2C The above table might be outdated, when you read this. If you suspect the table above to be outdated, you might want to have a look at server/drivers/hd44780-drivers.h in LCDproc's source directory which contains the actual translation code. Speed= BITRATE For a serial connection, set to the serial port bitrate. To use the default value for the chosen interface, just set to 0. Charmap= hd44780_default ea_ks0073 You need to set this parameter only if you do not have a standard HD44780 display. ea_ks0073 is the charmap for Electronic Assembly's KS0073 based displays. These devices have a richer charset, including many icons and many more characters of the ISO-8859-1 than standard HD44780s. Refer to hd44780-charset.h for more information. Keypad= yes no Tell whether you have a keypad connected. You may also need to configure the keypad layout further on in this file. Contrast= CONTRAST Set the initial contrast for the bwctusb connection type. Legal values for CONTRAST are 0 - 1000. If not given, it defaults to 300. Backlight= yes no Specifiy if you have a switchable backlight. OutputPort= yes no Tell if you have the additional output port ("bargraph") and you want to be able to control it with the lcdproc OUTPUT command. Lastline= yes no Specifies whether the lowest pixel line of a character is pixel addressable or if it controls an underline effect. The default is yes, meaning a pixel addressable last pixel line. Size= WIDTH x HEIGHT Specifies the size of the LCD. Default: 20x4 In case of multiple combined displays, this should be the total size. vSpan= HEIGHT ,… The "vertical span" when using multiple displays or multi-controller displays. It is a comma separated list of the heights of each display. In multi-controller displays it lists the number of lines each controller is responsible for. E.g. VSpan=2,2 means you have two displays and each has two lines. The sum of the HEIGHTs must match the total height given in Size=. ExtendedMode= yes no If you have a KS0073 or an other 'almost HD44780-compatible', set this flag to get into extended mode (4-line linear). This flag is NOT the old obsolete Extended option. DelayMult= DELAY If your display is slow and cannot keep up with the flow of data from LCDd, garbage can appear on the LCDd. Set this delay multiplier to 2 or 4 to increase the delays. The default is 1 for a non-multiplied delay. DelayBus= yes no You can reduce the inserted delays by setting this to no. On fast PCs it is possible your LCD does not respond correctly. Default: yes. KeepAliveDisplay= SECONDS Some displays (e.g. vdr-wakeup) need a message from the driver to that it is still alive. When set to a value bigger then 0 the character in the upper left corner is updated every SECONDS seconds. The default 0 does not cause any extra updates. RefreshDisplay= SECONDS If you experience occasional garbage on your display you can use this option as workaround. If set to a value bigger than 0 it forces a full screen refresh SECONDS seconds. Default: 0. DirectKey_NUM= KEY KeyMatrix_X_Y= KEY If you have a keypad you can assign keystrings to the keys. See documentation for used terms and how to wire it. To map, for example, the directly connected key 4 to the string Enter, use KeyDirect_4=Enter. For matrix keys use the X and Y coordinates of the key; e.g. KeyMatrix_1_3=Enter. This text has originally been 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@robijn.net Converted to docbook March 2002, Rene Wagner reenoo@gmx.de Updated April 2002, Rene Wagner reenoo@gmx.de Updated and extended April 2006, Peter Marschall peter@adpm.de