Project showcase
Office Status Marquee

Office Status Marquee © CC BY-NC-SA

People can see from outside my office when I'm on a video call or in a conference - or even on vacation.

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Components and supplies

About this project

For years I've had many people come to see me in my office and struggle with understanding that I'm on a video call with someone from my computer. So when I started working on Arduino for my chicken coop - more to come later - I came across the 8x8 LED matrix and the ability to gang them together. No I have a 64x8 scrolling marquee that allows me to announce to my visitors that I'm on a call, or out to lunch, or anything else that I have pre-programmed into my RS232 interface to control the marquee. Depending on the length of the message it may even scroll!

I used the examples from the MD_MAX72XX library to help me piece these together.

Here's a video of one scrolling message:

Scrolling Marquee

Code

My Scrolling MarqueeArduino
My first public posting of code. Please feel free to comment back with suggestions. I used 2 samples and pieced them together based on the status of D2 for controlling of scrolling the message.
// kayaking_t
// my office marquee - currently connected via Contact Closure and RS232 to a Crestron MP3E for message control.
//
// Use the MD_MAX72XX library to scroll text on the display
//
// Demonstrates the use of the callback function to control what
// is scrolled on the display text.
//
// User can enter text on the serial monitor and this will display as a
// scrolling message on the display.
// Speed for the display is controlled by a pot on SPEED_IN analog in.

#include <MD_MAX72xx.h>
#include <SPI.h>

#define PRINT_CALLBACK  0

#define PRINT(s, v) { Serial.print(F(s)); Serial.print(v); }

// Define the number of devices we have in the chain and the hardware interface
// NOTE: These pin numbers will probably not work with your hardware and may
// need to be adapted
#define HARDWARE_TYPE MD_MAX72XX::FC16_HW
#define MAX_DEVICES 8

#define CLK_PIN   13  // Digital or SCK - // originally pin 13
#define DATA_PIN  11  // PWM or MOSI - // originally pin 11
#define CS_PIN    10  // PWM or SS - // originally pin 10

// SPI hardware interface
MD_MAX72XX mx = MD_MAX72XX(HARDWARE_TYPE, CS_PIN, MAX_DEVICES);

// Scrolling parameters
#define SCROLL_DELAY  75  // in milliseconds

#define CHAR_SPACING  1 // pixels between characters

// Global message buffers shared by Serial and Scrolling functions
#define BUF_SIZE  75
char curMessage[BUF_SIZE];
char newMessage[BUF_SIZE];
bool newMessageAvailable = false;

uint16_t  scrollDelay;  // in milliseconds

// scrolling/static switch status
const int scrollSwitch = 2;
int scrollYes = 0;

void readSerial(void)
{
  static uint8_t  putIndex = 0;

  while (Serial.available())
  {
    newMessage[putIndex] = (char)Serial.read();
    //Serial.println(newMessage);
    if ((newMessage[putIndex] == '\n') || (putIndex >= BUF_SIZE-3)) // end of message character or full buffer
    {
      // put in a message separator and end the string
      newMessage[putIndex++] = ' ';
      newMessage[putIndex] = '\0';
      // restart the index for next filling spree and flag we have a message waiting
      putIndex = 0;
      newMessageAvailable = true;
    }
    else if (newMessage[putIndex] != '\r')
      // Just save the next char in next location
      putIndex++;
  }
}

void scrollDataSink(uint8_t dev, MD_MAX72XX::transformType_t t, uint8_t col)
// Callback function for data that is being scrolled off the display
{
#if PRINT_CALLBACK
  Serial.print("\n cb ");
  Serial.print(dev);
  Serial.print(' ');
  Serial.print(t);
  Serial.print(' ');
  Serial.println(col);
#endif
}

uint8_t scrollDataSource(uint8_t dev, MD_MAX72XX::transformType_t t)
// Callback function for data that is required for scrolling into the display
{
  static char   *p = curMessage;
  static uint8_t  state = 0;
  static uint8_t  curLen, showLen;
  static uint8_t  cBuf[8];
  uint8_t colData;

  // finite state machine to control what we do on the callback
  switch(state)
  {
    case 0: // Load the next character from the font table
      showLen = mx.getChar(*p++, sizeof(cBuf)/sizeof(cBuf[0]), cBuf);
      curLen = 0;
      state++;

      // if we reached end of message, reset the message pointer
      if (*p == '\0')
      {
        p = curMessage;     // reset the pointer to start of message
        if (newMessageAvailable)  // there is a new message waiting
        {
          strcpy(curMessage, newMessage);	// copy it in
          newMessageAvailable = false;
        }
      }
      // !! deliberately fall through to next state to start displaying

    case 1: // display the next part of the character
      colData = cBuf[curLen++];
      if (curLen == showLen)
      {
        showLen = CHAR_SPACING;
        curLen = 0;
        state = 2;
      }
      break;

    case 2: // display inter-character spacing (blank column)
      colData = 0;
      curLen++;
      if (curLen == showLen)
        state = 0;
      break;

    default:
      state = 0;
  }

  return(colData);
}

 void scrollText(void)
{
  static uint32_t	prevTime = 0;

  // Is it time to scroll the text?
  if (millis()-prevTime >= scrollDelay)
  {
    mx.transform(MD_MAX72XX::TSL);  // scroll along - the callback will load all the data
    prevTime = millis();      // starting point for next time
  }
}

void printText(uint8_t modStart, uint8_t modEnd, char *pMsg)
// Print the text string to the LED matrix modules specified.
// Message area is padded with blank columns after printing.
{
  uint8_t   state = 0;
  uint8_t   curLen;
  uint16_t  showLen;
  uint8_t   cBuf[8];
  int16_t   col = ((modEnd + 1) * COL_SIZE) - 1;

  mx.control(modStart, modEnd, MD_MAX72XX::UPDATE, MD_MAX72XX::OFF);

  do     // finite state machine to print the characters in the space available
  {
    switch(state)
    {
      case 0: // Load the next character from the font table
        // if we reached end of message, reset the message pointer
        if (*pMsg == '\0')
        {
          showLen = col - (modEnd * COL_SIZE);  // padding characters
          state = 2;
          break;
        }

        // retrieve the next character form the font file
        showLen = mx.getChar(*pMsg++, sizeof(cBuf)/sizeof(cBuf[0]), cBuf);
        curLen = 0;
        state++;
        // !! deliberately fall through to next state to start displaying

      case 1: // display the next part of the character
        mx.setColumn(col--, cBuf[curLen++]);

        // done with font character, now display the space between chars
        if (curLen == showLen)
        {
          showLen = CHAR_SPACING;
          state = 2;
        }
        break;

      case 2: // initialize state for displaying empty columns
        curLen = 0;
        state++;
        // fall through

      case 3:  // display inter-character spacing or end of message padding (blank columns)
        mx.setColumn(col--, 0);
        curLen++;
        if (curLen == showLen)
          state = 0;
        break;

      default:
        col = -1;   // this definitely ends the do loop
    }
  } while (col >= (modStart * COL_SIZE));

  mx.control(modStart, modEnd, MD_MAX72XX::UPDATE, MD_MAX72XX::ON);
}




void setup()
{
  mx.begin();
  mx.setShiftDataInCallback(scrollDataSource);
  mx.setShiftDataOutCallback(scrollDataSink);

  scrollDelay = SCROLL_DELAY;

  strcpy(curMessage, "AV Rocks!        ");
  newMessage[0] = '\0';

  Serial.begin(57600);
  Serial.print("\n[MD_MAX72XX Message Display]\nType a message for the scrolling display\nEnd message line with a newline");
}

void loop()
{
  scrollYes = digitalRead(scrollSwitch);
  readSerial();
  if (scrollYes == 0){
    printText(0, MAX_DEVICES-1, newMessage);
  } else {
    scrollText();
  }
}

Custom parts and enclosures

Oak Enclosure
Not 100% accurate as I did have to make some modifications during installation.
scrolling_led_case_k8dMtTwR4U.dwg

Schematics

Office Marquee
Here's the fritzing file - my first attempt...
tal_office_232_v2_0zh8MUxuvN.fzz

Comments

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