Adding a function to print scrolling text to the display

Max72xxPanel.cpp

@@ -14,6 +14,7 @@
  All text above must be included in any redistribution.
  ******************************************************************/
 
+#include "Arduino.h"
 #include <Adafruit_GFX.h>
 #include "Max72xxPanel.h"
 #include <SPI.h>
@@ -192,3 +193,31 @@ void Max72xxPanel::spiTransfer(byte opcode, byte data) {
 	// Latch the data onto the display(s)
 	digitalWrite(SPI_CS, HIGH);
 }
+
+void Max72xxPanel::printToDisplay(String tape, int wait, int letter_width, int spacer) {
+	spacer += 1;
+	letter_width += 6;
+
+  	letter_width += spacer; // Add the spacer width to the letter width to get the real width
+	int matrix_width = this->Adafruit_GFX::width();
+	int height = this->Adafruit_GFX::height();
+
+	for(int i = 0; i < letter_width * tape.length() + matrix_width - 1 - spacer; i++) {
+		this->fillScreen(LOW);
+
+		int letter = i / letter_width;
+	int x = (matrix_width - 1) - i % letter_width;
+	int y = (height - 8) / 2; // center the text vertically
+
+	while(x + letter_width - spacer >= 0 && letter >= 0) {
+		if(letter < tape.length()) {
+			this->Adafruit_GFX::drawChar(x, y, tape[letter], HIGH, LOW, 1);
+		}
+
+		letter--;
+	  x -= letter_width;
+	}
+	this->write();
+	delay(wait);
+	}
+}

Max72xxPanel.h

@@ -99,6 +99,15 @@ class Max72xxPanel : public Adafruit_GFX {
    */
   void write();
 
+  /*
+   * Writes a tape to the display in scrolling text format
+   * Parameters:
+   * spacer is space between letters
+   * letter_width is letter width
+   * wait controls the speed of text flow
+   */
+  void printToDisplay(String tape, int wait, int letter_width = 0, int spacer = 0);
+
 private:
   byte SPI_CS; /* SPI chip selection */
 
@@ -115,6 +124,3 @@ class Max72xxPanel : public Adafruit_GFX {
 };
 
 #endif	// Max72xxPanel_h
-
-
-

README.md

@@ -1,17 +1,18 @@
-Max72xxPanel
-============
+# TinkerTech Max72xxPanel Arduino Library
 
 An Arduino library for controlling a canvas of sets of 8x8 LEDs driven by MAX7219 or MAX7221 controllers. [Kits][hardware] sold for below 10 USD.
 
-This is a plugin for Adafruit's core graphics library GFX, providing basic graphics primitives (points, lines, circles, characters, etc.). So besides this library, you need to download and install [Adafruit_GFX][gfx-download], *dated Jul 5th, 2013 or more recent*. 
+This is a plugin for Adafruit's core graphics library GFX, providing basic graphics primitives (points, lines, circles, characters, etc.). So besides this library, you need to download and install [Adafruit_GFX][gfx-download], *dated Jul 5th, 2013 or more recent*.
 
-Written by Mark Ruys, <mark@paracas.nl>, 2013.
+Created by Mark Ruys, <mark@paracas.nl>, 2013.
+
+Edited by Patrick Neggie <patmn@umich.edu> 2018.
 
 
 Installation
 ------------
 
-Place the [Max72xxPanel][download] and [Adafruit_GFX][gfx-download] library folders in your `<arduinosketchfolder>/libraries/` folder. You may need to create the `libraries` subfolder if its your first library. Restart the Arduino IDE. 
+Place the [Max72xxPanel][download] and [Adafruit_GFX][gfx-download] library folders in your `<arduinosketchfolder>/libraries/` folder. You may need to create the `libraries` subfolder if its your first library. Restart the Arduino IDE.
 
 
 Features
@@ -21,6 +22,11 @@ Features
 - Uses the [SPI library][spi] to address the display(s) connected in cascade.
 - Low memory footprint.
 - Fast, no use of NOOP's.
+- Easy usage, one-line function to print text to display
+
+Notable Additions
+-----
+A new function in the format `void printToDisplay(String tape, int wait)` takes in a two parameters: a string of what to print to the display and a integer wait time to change how fast the text scrolls on the display.
 
 Usage
 -----
@@ -37,4 +43,4 @@ At YouTube, you'll find a [ticker tape][tickertape] and [snake] demo.
 [hardware]: https://www.google.com/search?q=MAX7219+Red+Dot+Matrix+Module "For kits, google MAX7219 Red Dot Matrix Module"
 [spi]: http://arduino.cc/en/Reference/SPI "SPI library"
 [tickertape]: http://www.youtube.com/watch?v=a8T7ZFeaf1A "Max72xxPanel Arduino library demo (ticker tape)"
-[snake]: http://www.youtube.com/watch?v=FbJJyuCwohs "Max72xxPanel Arduino library demo (snake)"
+[snake]: http://www.youtube.com/watch?v=FbJJyuCwohs "Max72xxPanel Arduino library demo (snake)"

examples/ScrollingText/ScrollingText.ino

@@ -0,0 +1,37 @@
+#include <SPI.h>
+#include <Adafruit_GFX.h>
+#include <Max72xxPanel.h>
+
+int pinCS = 10; // Attach CS to this pin, DIN to MOSI and CLK to SCK (cf http://arduino.cc/en/Reference/SPI )
+// i.e. connect CS to 10, DIN to 11, CLK to 13 for Arduino Uno
+int numberOfHorizontalDisplays = 8;
+int numberOfVerticalDisplays = 1;
+
+Max72xxPanel matrix = Max72xxPanel(pinCS, numberOfHorizontalDisplays, numberOfVerticalDisplays);
+
+String tape = "Hello :)";
+int wait = 20; // In milliseconds
+
+void setup() {
+
+  matrix.setIntensity(7); // Use a value between 0 and 15 for brightness
+
+/*
+ * the two for loops below may need to be modified
+ * depending on the ordering and orientation of your displays
+ */
+
+ // the setPosition function is responsible for the ordering of displays
+  for(int i = 0; i < 4; i++) {
+    matrix.setPosition(i, i, 0);  // The i'th display is at <i, 0>
+  }
+
+  // the setRotation function is responsible for the orientation of displays
+  for(int i = 0; i < 8; i++) {
+    matrix.setRotation(i, 1);     // rotate all displays 90 degrees
+  }
+}
+
+void loop() {
+  matrix.printToDisplay(tape, wait);
+}