The LCD backpack (aka. K107) board interfaces any HD44780-based LCD (this is the vast majority of LCD’s you will encounter) with a three-wire serial interface, consisting of +5volts, ground and serial data. The board uses a programmed PIC chip, created by Maryland EE professor Peter Anderson, to convert serial commands (e.g. Serial.print(“Freeduino”) ) into LCD text.
This boards turns any inexpensive (HD44780-compatible) LCD into a serial LCD.
Hook up power, ground and data and you’re good to go. No fussy libraries or handfuls of wires. Peter Anderson’s feaure set is really robust. You can check the command summary and sample code below.
This board is engineered for microcontrollers. Brian Riley of wulfden.org has a similar board but his includes an inverter option. If you need to hook up an LCD directly to a computer RS232 serial port get his board.
Board is currently available through Modern Device.
Custom Character Definitions
The character strings found below can be used to define custom characters when using the K107 backpack.
- 040E0E0E0E1F0004 => BELL
- 00000103161C0800 => CHECKMARK
Command Summary
Reference adopted from http://phanderson.com/lcd106/lcd107.html
Some commands require a delay to ensure proper transmission.
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Command / Comments |
Suggested Pause |
Example |
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Send Text |
Serial.print(“Hello World!”); |
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?a |
Home Cursor |
Serial.print(“?a”); |
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?b |
Destructive Backspace |
Serial.print(“?b”); // backspace |
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?c# |
Set Cursor Style: 0= none 2= blinking 3=underline |
(“?c0”); // turn cursor off |
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?f |
Clear Screen |
Serial.print(“?f”); |
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?g |
Beep (requires speaker on pin 6) |
Serial.print(“?g”); |
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?h |
Backup Cursor (Non-destructive backspace) |
Serial.print(“?h”); |
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?i |
Forward cursor |
Serial.print(“?i”); |
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?j |
Up cursor |
Serial.print(“?j”); |
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?k |
Down cursor |
Serial.print(“?k”); |
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?l |
Clear cursor line |
Serial.print(“?k”); |
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?m |
Carriage Return |
Serial.print(“?m”); |
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?n |
CRLF, carriage return & line feed, |
Serial.print(“?n”); |
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?s# |
Set tabs at # spaces |
100 ms |
Serial.print(“?s7”); |
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?t |
Tab, advance one tab position |
Serial.print(“?t”); |
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?x## |
Position cursor on x column, (two characters are required), first column is column 0 |
Serial.print(“?x09”); |
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?y# |
Position cursor at y row, first row is row 0, |
Serial.print(“?y3”); |
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?? |
Display a “?” |
Serial.print(“??”); |
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?! |
Send direct command to LCD |
Serial.print(“?!01”); |
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?B |
Backlight Intensity – sets PWM value, two hex digits req. (00 to FF) |
100 ms |
Serial.print(“?BFF”); |
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?D# |
Define Character “?D#1A001A001A001A00” D# = character |
100 ms |
Serial.print(“?D31F001F001F001F00”); |
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?# |
Print a custom character |
5 ms |
Serial.print(“?3); |
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?H |
High output on auxiliary digital pins: valid numbers are 4,5,6 |
Serial.print(“?H4”); |
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?L |
Low output on auxiliary digital pins: valid numbers are 4,5,6 |
Serial.print(“?L4”); // aux pin 4 LOW |
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?G |
Configure for LCD geometry. Supported formats: |
Serial.print(“?G216”); |
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Ganging up commands is OK, except for commands requiring a following pause |
Serial.print(“?x01?y1?fHello World”); |
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Enhanced Commands |
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?># |
Enter BIG Number Mode (numbers only!) “?>3” X # = 3 or 4 , # represents number of characters displayed. (20×4 LCD’s only) |
100 ms |
Serial.print(“?>4”); |
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?< |
Exit BIG number mode “?<“ |
Serial.print(“?<“); |
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?C# |
Define custom boot screen line # = 0 – 3 |
100 ms |
Serial.print(“?C0abcdefghijklmnopqrst”) |
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?S# |
“?S0” – display no screen on boot. |
Serial.print(“?S2); // custom boot screen |
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| ?* | display boot screen at any time | Serial.print(“?*); // show boot screen |
6 Comments
pixel · 02/03/2012 at 15:31
The LCD geometry is definitely your problem. LCD’s use addresses to reference each character position on the display but the addresses from line to line are not sequential. For example on a 4×16 LCD the addresses work like this:
Address
0x00-0x15 – Line 1
0x32-0x47 – Line 2
0x16-0x31 – Line 3
0x48-0x63 – Line 4
You will notice that when you reach the end of the line and keep printing characters they start appearing on line 3 NOT line 2 because of how the address space is organized. This also causes all kinds of problems when the K107 thinks it is using a different sized display than it actually is because all the positioning the K107 does is based on these address ranges.
Now to actually solve the problem you will need to tell the K107 board that it is driving a 4×20 so that it knows how to ‘chop up’ the address space. For the K107 this is super simple and only needs to be configured once when you plug in a new LCD with a different geometry. It remembers the geometry between disconnects.
To set the geometry for your display you need to send the “?G” command (which is explained above) with the number of lines followed by the width of the display (in characters). So for a 4×20 display you would send the string “?G420” at which point you should be all set.
Hopefully that should fix things.