2 Sparkfun’s 7-Segment Red 6.5? Display and Arduino

A few weeks ago I posted about connecting Sparkfun’s 7-Segment 6.5″ Display’s to Arduino. In that post I only showed how to hook up 1 digit. In this post I will show how to hook up 2, but it scales to however many you want to add. Much of the same applies from my previous post but here are new diagrams and code.

 
int dataPin = 11;
int clockPin = 12;
int latchPin = 8;
 
int len = 10;
 
//holders for infromation you're going to pass to shifting function
byte dataRED;
byte dataArrayRED[10];
 
byte off = 0x00;
byte decimalpoint = 0x80;
 
 
 
void setup() {
 
  //set pins to output because they are addressed in the main loop
  pinMode(latchPin, OUTPUT);
 
  //Arduino doesn't seem to have a way to write binary straight into the code
  //so these values are in HEX.  Decimal would have been fine, too.
 
  dataArrayRED[0] = 0x3F; //00111111 - 0
  dataArrayRED[1] = 0x06; //00000110 - 1
  dataArrayRED[2] = 0x5B; //01011011 - 2
  dataArrayRED[3] = 0x4F; //01001111 - 3
  dataArrayRED[4] = 0x66; //01100110 - 4
  dataArrayRED[5] = 0x6D; //01101101 - 5
  dataArrayRED[6] = 0x7D; //01111101 - 6
  dataArrayRED[7] = 0x07; //00000111 - 7
  dataArrayRED[8] = 0x7F; //01111111 - 8
  dataArrayRED[9] = 0x67; //01100111 - 9
 
}
 
void loop() {
 
int count = 100;
int val = 10; //this is for how many digits
 
 
 
for( int i = 0; i<count; i++ )
{
  digitalWrite(latchPin, 0);
 
 
   int digit2 = i % val;
  int digit1 = ( i - digit2 ) / val;
 
    shiftOut(dataPin, clockPin, dataArrayRED[ digit2 ]);
    shiftOut(dataPin, clockPin, dataArrayRED[ digit1 ]);
 
  digitalWrite(latchPin, 1);
  delay(300);
  delay(1000);
}
 
}
 
 
// the heart of the program
void shiftOut(int myDataPin, int myClockPin, byte myDataOut) {
  // This shifts 8 bits out MSB first,
  //on the rising edge of the clock,
  //clock idles low
 
  //internal function setup
  int i=0;
  int pinState;
  pinMode(myClockPin, OUTPUT);
  pinMode(myDataPin, OUTPUT);
 
  //clear everything out just in case to
  //prepare shift register for bit shifting
  digitalWrite(myDataPin, 0);
  digitalWrite(myClockPin, 0);
 
  //for each bit in the byte myDataOut…
  //NOTICE THAT WE ARE COUNTING DOWN in our for loop
  //This means that %00000001 or "1" will go through such
  //that it will be pin Q0 that lights.
 
  for (i=7; i>=0; i--)  
  {
    digitalWrite(myClockPin, 0);
 
    //if the value passed to myDataOut and a bitmask result
    // true then... so if we are at i=6 and our value is
    // %11010100 it would the code compares it to %01000000
    // and proceeds to set pinState to 1.
    if( myDataOut & (1<<i) ) 
    {
	pinState= 1;
    }
    else 
    {
	pinState= 0;
    }
 
    //Sets the pin to HIGH or LOW depending on pinState
 
    digitalWrite(myDataPin, pinState);
    //register shifts bits on upstroke of clock pin
    digitalWrite(myClockPin, 1);
    //zero the data pin after shift to prevent bleed through
    digitalWrite(myDataPin, 0);
  }
 
  //stop shifting
  digitalWrite(myClockPin, 0);
}

I also have a video uploaded on viddler

Now that I have this up and running I just have to do something useful with it. And I have to find a better way to solder the digits, because there are wires everywhere.

Continue reading » · Rating: · Written on: 06-19-09 · 13 Comments »

Sparkfun’s 7-Segment Red 6.5″ Display and Arduino

A little while ago I purchased 10 of Sparkfun’s 7-segment red 6.5″ displays.

http://www.sparkfun.com/commerce/product_info.php?products_id=8530

I had been wanting to purchase them for quite some time but they had been out of stock. When I was finally notified that they had received more I instantly bought them, without really thinking what I was going to use them for. Once they arrived I quickly opened them up and saw that it was going to be a little bit more of a challenge then I originally thought it would be. And I also thought they would come with some fancy schematic that I could just follow, but they didn’t.

So the first step was just to try and get a segment to light up by just supplying power. The digits use a common anode, which means it has one lead connection and 7 ground connection for each segment. So I started running it through a 5v power supply with not luck. Then a 9v, still no luck. Finally 12v did the trick. After I soldered wires to all of the connection I was able to get all 7 segments to light up by just running the common anode to the power and each segment to a ground.

Ok so step one complete now to try and get it talking with Arduino. Now I wasn’t really sure how to go about doing this since each segment was connected to a ground. So I started digging around on the Arduino forums and found some similar posts on what I was trying to do. My conclusion was that I need to get a shift register to turn each segment on and off. I found some people who had some luck with this display and the Allegro 6278EAT. You can pick some up for $1.55 at Digi Key. There are lots of different LED drivers out there but the reason I chose this one was because I needed to supply 12v to my displays and it sounded like some of the others that people where recommending wouldn’t work.

So after a lot of experimenting and researching I was finally able to get the display to turn on and off with Arduino. This tutorial on the Arduino site was the most helpful. And I used the following Arduino sketch which I got from this post on the forums.

int dataPin = 11;
int clockPin = 12;
int latchPin = 10;
 
//holders for infromation you're going to pass to shifting function
byte dataRED;
 
byte dataArrayRED[11];
 
void setup() {
 
  //set pins to output because they are addressed in the main loop
  pinMode(latchPin, OUTPUT);
 
  //Arduino doesn't seem to have a way to write binary straight into the code
  //so these values are in HEX.  Decimal would have been fine, too.
  dataArrayRED[0] = 0x3F; //00111111 - 0
  dataArrayRED[1] = 0x06; //00000110 - 1
  dataArrayRED[2] = 0x5B; //01011011 - 2
  dataArrayRED[3] = 0x4F; //01001111 - 3
  dataArrayRED[4] = 0x66; //01100110 - 4
  dataArrayRED[5] = 0x6D; //01101101 - 5
  dataArrayRED[6] = 0x7D; //01111101 - 6
  dataArrayRED[7] = 0x07; //00000111 - 7
  dataArrayRED[8] = 0x7F; //01111111 - 8
  dataArrayRED[9] = 0x67; //01100111 - 9
  dataArrayRED[10] = 0x80; //decimal point
}
 
void loop() {
 
for (int i = 0; i&lt;11; i++)
{
 
  dataRED = dataArrayRED[i];
 
    //ground latchPin and hold low for as long as you are transmitting
 
    digitalWrite(latchPin, 0);
    //move 'em out
 
    shiftOut(dataPin, clockPin, dataRED);
    //return the latch pin high to signal chip that it
    //no longer needs to listen for information
    digitalWrite(latchPin, 1);
    delay(300);
 
  delay(1000);
}
 
}
 
// the heart of the program
void shiftOut(int myDataPin, int myClockPin, byte myDataOut) {
  // This shifts 8 bits out MSB first,
  //on the rising edge of the clock,
  //clock idles low
 
  //internal function setup
  int i=0;
  int pinState;
  pinMode(myClockPin, OUTPUT);
  pinMode(myDataPin, OUTPUT);
 
  //clear everything out just in case to
  //prepare shift register for bit shifting
  digitalWrite(myDataPin, 0);
  digitalWrite(myClockPin, 0);
 
  //for each bit in the byte myDataOut…
  //NOTICE THAT WE ARE COUNTING DOWN in our for loop
  //This means that %00000001 or "1" will go through such
  //that it will be pin Q0 that lights.
  for (i=7; i&gt;=0; i--)
  {
    digitalWrite(myClockPin, 0);
 
    //if the value passed to myDataOut and a bitmask result
    // true then... so if we are at i=6 and our value is
    // %11010100 it would the code compares it to %01000000
    // and proceeds to set pinState to 1.
    if( myDataOut &amp; (1&lt;
    {
	pinState= 1;
    }
    else
    {
	pinState= 0;
    }
 
    //Sets the pin to HIGH or LOW depending on pinState
    digitalWrite(myDataPin, pinState);
    //register shifts bits on upstroke of clock pin
    digitalWrite(myClockPin, 1);
    //zero the data pin after shift to prevent bleed through
    digitalWrite(myDataPin, 0);
  }
 
  //stop shifting
  digitalWrite(myClockPin, 0);
}

And here is a final diagram for connecting it to Arduino.

NOTE: the diagram shows a 15kohm resistor but it may not be bright enough. If you put a 2.2kohm resistor it will be much brighter

And here is a video of the display counting – http://www.viddler.com/explore/julian/videos/14/

I am working on getting more then one display working and will write a new post when I do

Continue reading » · Rating: · Written on: 05-30-09 · 4 Comments »