9.1 KiB
I2C_LCD
Arduino library for I2C_LCD LCD displays.
Warning: experimental with side effects, use at own risk
do not overfeed your display with too much data too fast as it may not be able to handle. During longer tests my 20x4 display garbled too often. Under investigation.
Description
Experimental Arduino library for the I2C LCD display, typical 20x4 characters.
The library is inspired by the excellent LiquidCrystel_I2C library of F. Malpartida. Therefore the interface is kept quite identical, extended with some additional functions. The goal of the library is to minimize footprint and improve performance. This is partly done by dedicate the library to I2C only.
The library implements the print interface, so all data types are printable assuming they fit on the display.
The reference:
Additional functions not in the reference
| name | description |
|---|---|
| isConnected() | test if display address is seen on I2C bus. |
| clearEOL() | clears line from current position |
| \t | printing of a tab char moves to next multiple of 4. |
| special(index) | prints the customized char at index (0..7) |
| center(row, str) | centers a char array on chosen row. |
| right(col, row, str) | right align a char array from chosen position. |
Compatibility
Reasonable compatible with F. Malpartida's I2C library, relative minor differences mostly in the constructors. Furthermore the current version does not support all functionality, and more important it is not tested as much as the reference. Only the 5x8 font is supported.
So if you need full functionality, robustness or reliability, you should use the reference New-liquidCrystal library.
Tests
Tested on an UNO and a 20x4 character LCD, and limited on a 16x2 LCD.
Performance
The most important optimization is to send every byte in a single I2C transaction. This takes 5 bytes to transport, which is 3 less than the reference.
Furthermore there is an optimization if the pins are in ascending order, as then it is far easier to get the nibble (half bytes) to send.
First performance tests are good. See example I2C_LCD_performance.ino.
The performance measurement is done on an UNO, data pins are in ascending order.
| I2C clock | 0.1.0 | 0.1.1 | notes |
|---|---|---|---|
| 100000 | 4316 | 4640 | |
| 200000 | 2440 | 2760 | |
| 300000 | 1780 | 2108 | |
| 400000 | 1496 | 1820 | (1) |
| 500000 | 1308 | 1632 | |
| 600000 | 1176 | 1500 | |
| 700000 | 1076 | 1400 | |
| 800000 | 1024 | 1348 |
Note 1: 0.1.0 problems with spectrum examples - too much data too fast killed my display.
Timing in the 0.1.1 version is roughly 400 us slower than 0.1.0 for 8 characters. However the 0.1.1 is more robust as far as tested.
Note: Performance is also a matter of developing an optimal algorithm. This is often a trade between code size, memory used and speed. See I2C_LCD_demo_spectrum_row.ino for an example.
Related
- https://github.com/fmalpartida/New-LiquidCrystal The reference.
- https://github.com/RobTillaart/ANSI for VT100 alike terminals.
Interface
#include "I2C_LCD.h"
Constructor
- I2C_LCD(uint8_t address, TwoWire * wire = &Wire) Constructor, mandatory address and optional alternative I2C bus.
- void config(uint8_t address, uint8_t enable, uint8_t readWrite, uint8_t registerSelect, uint8_t data4, uint8_t data5, uint8_t data6, uint8_t data7, uint8_t backlight, uint8_t polarity) pin configuration. Will change in the future.
- void begin(uint8_t cols = 20, uint8_t rows = 4) initializes library size. User must call the appropriate Wire.begin() before calling lcd.begin(()
- bool isConnected() returns true if address can be seen on the I2C bus chosen.
Backlight
- void setBacklightPin(uint8_t pin, uint8_t polarity) idem.
- void setBacklight(bool on) idem.
- void backlight() wrapper for setBacklight()
- void noBacklight() wrapper for setBacklight()
Display
- void display() set display on
- void noDisplay() set display off
- void on() set display on
- void off() set display off
Positioning and cursor
- void clear() clear whole screen and set cursor to 0, 0.
- void clearEOL() clears line from current pos. NEW
- void home() set cursor to 0, 0.
- bool setCursor(uint8_t col, uint8_t row) set cursor to given position. There is a check if this is out of range, if so it return false.
- void noBlink() idem.
- void blink() idem.
- void noCursor() idem.
- void cursor() idem.
Miscellaneous
Minimal tested.
- void scrollDisplayLeft(void)
- void scrollDisplayRight(void)
- void moveCursorRight(void)
- void moveCursorLeft(void)
The next 4 have only limited support
(either autoscroll or leftright can be set, not both)
- void autoscroll(void)
- void noAutoscroll(void)
- void leftToRight(void)
- void rightToLeft(void)
Create your own characters
A charmap consists of an array of 8 bytes with values 0..31 (5 bits). There are 8 slots to place a special character, index 0..7. The custom characters can be printed with special(index) which is a wrapper around write((uint8_t)index)
- void createChar(uint8_t index, uint8_t * charmap)
- size_t special(uint8_t index) to print the special char.
See spectrum examples for how to use custom characters.
Print interface
- size_t write(uint8_t c)
Array writing not implemented as there are no gains seen.
Two helper functions, please note these work only with a char array.
- size_t center(uint8_t row, char * message) centers a string on the defined row.
- size_t right(uint8_t col, uint8_t row, char * message) right align a string. col is the align position.
Experimental
Tab printing
When '\t' (character 9) is printed to the LCD, it moves to the first position that is a multiple of 4. This allows a simple way to get some sort of tabular data representation. See the example.
Idea for the future might be to set the tab-stops instead of current hardcoded ones.
Debug
Position tracking
The library tries to keep track of the current position on the line it is. When going beyond the number of columns, it will not print any more. This protects against printing beyond screen position (and writing one some other line). Additional it saves some time.
This position tracking only works for "standard" use, no display scrolling, right to left mode etc. So it can cause unwanted side effects, which can be fixed by removing the "pos < cols" condition from write().
- uint8_t getColumn()
The library does not track the row (yet)
getWriteCount()
As I encountered problems during tests (display garbled) I added a counter of the number of writes (each char => 5 bytes I2C). For now a development only, so expect it to be removed in future.
- uint32_t getWriteCount() idem.
Not reset-able.
Future
Must
- update documentation
Should
- test, test, test
- test with other platforms
- test with other display sizes
Could
- add examples
- make an issue for New-LiquidCrystal library.
- function to define the tab-stops, instead of hard coded ones.
- make a separate include file for charmaps by name.
- investigate reading busy flag over I2C.
Wont for now.
- implement unit tests (possible?)
- add timestamp last print
- investigate other special characters to support, like
- \r => goto begin of current line
- \n => goto begin of next line
- FF => form feed is clear screen.
- BELL => blink of the display (oeps 7 is already a special char )
Support
If you appreciate my libraries, you can support the development and maintenance. Improve the quality of the libraries by providing issues and Pull Requests, or donate through PayPal or GitHub sponsors.
Thank you,