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LCDGraph API

Table of Contents

Including

Add these lines to the top of your main project file:

// Libraries to include
#include <LiquidCrystal.h>
#include <LCDGraph.h>

Constructor

LCDGraph<DataFormat=int16_t, LCDLibrary=LiquidCrystal>(uint8_t width, uint8_t height, uint8_t firstRegister)

Initialises the class. Currently, the height must be 1 as vertical tiling is not yet implemented.

  • DataFormat is a template and is the data format that will be expected when calling add and setting and reading yMax and yMin. This can be changed to a smaller data type such as a byte to save memory if needed or a larger one such as an unsigned long or float if larger or floating point numbers need to be displayed. Because each data type will require its own copy of the class, it is recommended that if possible, only a single data type is used accross all instances to save program memory.
  • LCDLibrary is a template for the library used to drive the display. By default it is set to the built in LiquidCrystal library, but has also been tested to work with the LiquidCrystal_I2C library.
  • width is the width in characters.
  • height is the height in characters on the display, but should be 1 currently.
  • firstRegister is the first register to use in the display. As there are only 8, they may need to be shared around.

For example, using 2 4 character wide graphs would be:

LCDGraph<int> graph1(4, 1, 0);
LCDGraph<int> graph2(4, 1, 4);

An 8 char wide graph must start at register 0 in the display, a 7 char wide at 0 or 1, ...

The height parameter can be left out if desired to default to a height of 1:

LCDGraph<DataFormat=int16_t, LCDLibrary=LiquidCrystal>(uint8_t width, uint8_t firstRegister)

Attributes

Name Data Type Comments Default
yMin DataFormat (specified in constructor) The current minimum of the Y axis. Can be written to to set it manually 0
yMax DataFormat (specified in constructor) The current maximum of the Y axis. Can be written to to set it manually 255
filled bool Whether everything under the line will be filled in true
showXAxis bool Whether to draw the X axis as a solid line. true
showYAxis bool Whether to draw the Y axis as a solid line. true
intercepts bool If true, makes any x and y axis intercepts display as an off pixel when axis are displayed so that points on axis do not disappear. Can be a bit misleading if the x axis is on the top or bottom of the display. false

Methods

void begin(LCDLibrary *lcd)

Gives the library the pointer to the lcd object to use. For example:

// Set up the lcd
lcd.begin(20, 4);
graph.begin(&lcd);

void add(DataFormat value)

Adds a data point to the internal graph circular buffer. Chucks out the earlist data point if the buffer is full.

void clear()

Removes all data from the circular buffer

void setRegisters()

Generates the custom characters from the data currently in the circular buffer and sends it to the custom character registers in the lcd. If any of the special characters or this graph are already on the display, they will be updated. Otherwise, display(uint8_t x, uint8_t y); needs to be called to draw the graph from the registers.

void display(uint8_t x, uint8_t y)

Displays the graph in the correct location on the display. setRegisters needs to be called beforehand to display the latest data. In all displays I have used, display only needs to be called once if the graph is going to be continually be updated in the same location.

void autoRescale(bool force0 = false, bool allowSmallerRange = true)

Rescales the graph to fit all data.

  • force0 will make sure that 0 is included as either the minimum or maximum if true. 0 will also be included as a limit if there is only a single value.
  • allowSmallerRange will allow yMin to increase and yMax to decrease to fit all current data. If false, the range can only expand (yMin decrease and yMax increase).

uint8_t length()

Returns the number of points in the circular buffer.

void end()

Deallocates the internal circular buffer from memory. It is preferable to only create the instance and use it as global (with clear() if necessary) for the entire time the program is running to avoid memory fragmentation issues.