DOTMATRIX

MBED library for MAX7219 driven 8x8 LED dot matrix's

Features

• Multiple display support
• Scrolling text
• Comes with built-in bit patterns
• Custom bit pattern display
• Each display individually controllable
• Full control over every display

Usage

Quick usage

Initialize matrix:

DOTMATRIX matrix(<clkPin>, <dinPin>, <csPin>, <number of displays>, <reverse displays>);

• matrix: name of choice.
• clkPin: pin on which the clk pin of the first display is connected. Must be a SPI sclk (e.g. PB_13)
• dinPin: pin on which the din pin of the first display is connected. Must be a SPI mosi (e.g. PB_15)
• csPin: pin on which the cs pin of the first display is connected (e.g. PC_1)
• number of displays: number of displays connected in series (e.g. 4)
• reverse displays: whether the displays are mounted upside down (e.g. false)

Initialize displays:

matrix.initDisplays();

Sets all displays to default mode (on, no test, normal decode, all 8 digits decode, intensity to 15)

Set scrolling text:

matrix.createIDArray(<text>);

• text: Text that will be displayed

Clear scrolling text:

matrix.clearIDArray();

Should be called before matrix.createIDArray() to clear buffer.

Update scrolling text:

matrix.update();

Makes a shiftText() and displayBitPatternAll()
Also when the last letter is displayed, start from the beginning
returns true if text starts from the beginning

Advanced usage

Set shutdown mode:

matrix.setShutdownMode(<displayNumber>, <shutdown>);

• displayNumber: number of display (-1 for all displays)
• shutdown: trueor false

Set scan limit:

matrix.setScanLimit(<displayNumber>, <scanLimit>);

• displayNumber: number of display (-1 for all displays)
• scanLimit: how many lines are dispalyed (0 -> 1 line, 7 -> all 8 lines)

Set decode mode:

matrix.setDecodeMode(<displayNumber> ,<decodeMode>);

• displayNumber: number of display (-1 for all displays)
• decodeMode: how many lines are dispalyed (0 -> 1 line, 7 -> all 8 lines)

Set display brightness:

matrix.setIntensity(<displayNumber>, <intensity>);

• displayNumber: number of display (-1 for all displays)
• intensity: brightness of display (from 0to 15)

Set display test:

matrix.setDisplayTest(<displayNumber>, <testMode>);

• displayNumber: number of display (-1 for all displays)
• testMode: trueor false

Set bit pattern for singe display:

matrix.displayBitPattern(<displayNumber>, <pattern>);

• displayNumber: number of display
• pattern: address of uint8_t array with 8 elemnts (e.g. &letterA)

Set bit pattern for all displays:

matrix.displayBitPatternAll(<pattern>);

• pattern: address of two dimesional uint8_t array with 8 elemnts per display (e.g. &textABC)

Load next bits of text

matrix.loadNextTextBits();

Shift Text 1 bit to the left

matrix.shiftText();

Reset display:

matrix.resetDisplay();

Resets the current displaying text back to the beginning

Send raw data to display

matrix.sendByte(<address>, <data>);

• address: address of register (see MAX7219 datasheet)
• data: data to load in the register (see MAX7219 datasheet)

Usage of text input

Decode table (input -> output (on display))

Normal characters

A -> A
B -> B
...
y -> y
z -> z

0 -> 0
...
9 -> 9

space -> small space (4 dot wide)
( -> (
) -> )
. -> .
, -> ,
_ -> _
- -> -
? -> ?
! -> !
: -> :

Special character (with % in front (e.g. %A -> Ä))

A -> Ä
a -> ä
...
ü -> ü

space -> space (8 dot wide)
1 -> one blank vertical line
2 -> two blank vertical lines
3 -> three blank vertical lines
| -> one filled vertical line

H -> Heart symbol
S -> Smiley face

Example

Basic scrolling text example

main(){
  DOTMATRIX matrix(PC_2, PC_0, PC_1, 4, false);
  matrix.initDisplays();
  matrix.createIDArray("Hello World!% % % %");
  while(true){
    matrix.update();
    thread_sleep_for(40);
  }
}

Limitations

• By default, only support up to 50 displays (can be changed in DOTMATRIX.h)
• By default, maximum text length is 500 characters (can be changed in DOTMATRIX.h)

Notes

• Tested on NUCLEO-L152RE (STM32)
• Tested with up to 26 displays