Fun with SLO2016 LED displays

I love going to hamfests; you never know what you will find.  At one 'fest a few years ago, I picked up several SLO2016 LED matrix displays. I had no idea what they were when I bought them -- they just looked kind of cool and I thought they might work for small, minimal displays (as opposed to a larger LCD display). After a quick web search, I found this data sheet.

They are modules of 4 little 5x7 LED matrix characters.  They have 7 data lines for 127 characters, 2 address lines to determine which character is updated, and a enable/write line.  They can be chained together by sharing the data and address lines and controlling the individual enable/write pin on each display.

I posted a video to youtube showing 3 displays chained together for a 12 character scrolling display controlled by an Arduino Pro Mini.  You can find several other videos with examples. 

I got a request for the code for the scrolling text.  I make no claim as to how wonderful my code is; if it is useful, have at it!

The Code

const int LED = 13; const int CLEAR_PIN = 7; const int ADDR0_PIN = 8; const int ADDR1_PIN = 9; const int LEFT_WRITE_PIN = 10; const int MIDDLE_WRITE_PIN = 11; const int RIGHT_WRITE_PIN = 12; const int SCROLL_PAUSE = 175; const String SPACES = " "; const String SCROLL_STRING = "This is a test of the interesting SLO-2016 LED matrix display. It's pretty awesome, dude!"; char ALL_CHARS[128]; const byte NUM_DISPLAY_CHARS = 12; void setup() { // DDRD = 0xFF; pinMode (0, OUTPUT); pinMode (1, OUTPUT); pinMode (2, OUTPUT); pinMode (3, OUTPUT); pinMode (4, OUTPUT); pinMode (5, OUTPUT); pinMode (6, OUTPUT); pinMode (LED, OUTPUT); pinMode (LEFT_WRITE_PIN, OUTPUT); pinMode (MIDDLE_WRITE_PIN, OUTPUT); pinMode (RIGHT_WRITE_PIN, OUTPUT); pinMode (ADDR0_PIN, OUTPUT); pinMode (ADDR1_PIN, OUTPUT); pinMode (CLEAR_PIN, OUTPUT); digitalWrite (LEFT_WRITE_PIN, HIGH); digitalWrite (MIDDLE_WRITE_PIN, HIGH); digitalWrite (RIGHT_WRITE_PIN, HIGH); digitalWrite (CLEAR_PIN, HIGH); for (byte i = 1; i < 127; i++) { ALL_CHARS[i] = i; } ALL_CHARS[0] = ' '; // can not set the zero byte (null char) in a string ALL_CHARS[127] = '\0'; // properly terminate string } void loop () { digitalWrite (LED, HIGH); displayClear (); delay (SCROLL_PAUSE); digitalWrite (LED, LOW); // displayString (" Hi!"); scrollString (SCROLL_STRING); scrollString (ALL_CHARS); delay (1000); } void displayClear () { digitalWrite (CLEAR_PIN, LOW); delay(10); digitalWrite (CLEAR_PIN, HIGH); } void scrollString (String str) { // Go through the given string 4 characters at a time. String visible = String (SPACES); byte strLen = str.length (); byte strIndex = 0; byte lastCharPos = NUM_DISPLAY_CHARS - 1; while (strIndex < strLen) { // move chars in visible string to the left // add the char at strIndex at right. char ch = str.charAt (strIndex); for (byte i = 0; i < lastCharPos; i++) { visible.setCharAt (i, visible.charAt(i+1)); } visible.setCharAt (lastCharPos, ch); displayString (visible); strIndex++; delay (SCROLL_PAUSE); } // add trailing spaces. for (byte count=0; count < NUM_DISPLAY_CHARS; count++) { for (byte i = 0; i < lastCharPos; i++) { visible.setCharAt (i, visible.charAt(i+1)); } visible.setCharAt (lastCharPos, ' '); displayString (visible); delay (SCROLL_PAUSE); } } void displayString (String str) { // Send characters to display byte len = str.length (); byte index = 0; while ((index < len) && (index < NUM_DISPLAY_CHARS)) { char ch = str[index]; displayChar (ch, index); index++; } } /* * Display a character in one position. * * ch - the character to display * addr - the character display address (0-3 left, 4-7 right display) */ void displayChar (char ch, byte addr) { digitalWrite (LED, HIGH); int write_pin = 0; // set the address pins switch (addr) { case 00: digitalWrite (ADDR0_PIN, HIGH); digitalWrite (ADDR1_PIN, HIGH); write_pin = LEFT_WRITE_PIN; break; case 1: digitalWrite (ADDR0_PIN, HIGH); digitalWrite (ADDR1_PIN, LOW); write_pin = LEFT_WRITE_PIN; break; case 2: digitalWrite (ADDR0_PIN, LOW); digitalWrite (ADDR1_PIN, HIGH); write_pin = LEFT_WRITE_PIN; break; case 3: digitalWrite (ADDR0_PIN, LOW); digitalWrite (ADDR1_PIN, LOW); write_pin = LEFT_WRITE_PIN; break; case 4: digitalWrite (ADDR0_PIN, HIGH); digitalWrite (ADDR1_PIN, HIGH); write_pin = MIDDLE_WRITE_PIN; break; case 5: digitalWrite (ADDR0_PIN, HIGH); digitalWrite (ADDR1_PIN, LOW); write_pin = MIDDLE_WRITE_PIN; break; case 6: digitalWrite (ADDR0_PIN, LOW); digitalWrite (ADDR1_PIN, HIGH); write_pin = MIDDLE_WRITE_PIN; break; case 7: digitalWrite (ADDR0_PIN, LOW); digitalWrite (ADDR1_PIN, LOW); write_pin = MIDDLE_WRITE_PIN; break; case 8: digitalWrite (ADDR0_PIN, HIGH); digitalWrite (ADDR1_PIN, HIGH); write_pin = RIGHT_WRITE_PIN; break; case 9: digitalWrite (ADDR0_PIN, HIGH); digitalWrite (ADDR1_PIN, LOW); write_pin = RIGHT_WRITE_PIN; break; case 10: digitalWrite (ADDR0_PIN, LOW); digitalWrite (ADDR1_PIN, HIGH); write_pin = RIGHT_WRITE_PIN; break; case 11: digitalWrite (ADDR0_PIN, LOW); digitalWrite (ADDR1_PIN, LOW); write_pin = RIGHT_WRITE_PIN; break; default: break; } digitalWrite (write_pin, LOW); PORTD = ch; digitalWrite (write_pin, HIGH); digitalWrite (LED, LOW); }