LED Matrix Display 5x7

Discussion in 'Homework Help' started by dag2p, Apr 21, 2009.

  1. dag2p

    Thread Starter New Member

    Apr 21, 2009
    2
    0
    I have a 5x7 LED Matrix Display project i'm stuck on and not quite sure where to start from. So here is what needs to be done. I am implementing this all with Programmable Logic on the Altera UP-2. I have a keypad (0-F) and when a character is pressed on the keypad it displays it on the 5x7 Matrix display.

    My question to you is how does one interface the keypad to the Flex 10k chip on the UP-2, i'm assuming in BCD, and then make a driver not using micro controllers for the LED Display to display the given character.

    Thanks for all your help in advance.
    Daniel G.
     
  2. StayatHomeElectronics

    Well-Known Member

    Sep 25, 2008
    864
    40
    The first thing you need to identify is what is the output of the keypad for each of the individual characters. Don't assume it's BCD, it might not be. It might be row and column or some other scheme. You have 16 inputs, 0 to 9 and A to F. How many bits come out of the keypad that must be hooked to the Altera board?

    Determine the same thing for the display. How do you communicate to the display? Are there 35 individual lines that go into the display or you need serial communication? Map out exactly what you need to send to the display for each key pressed.

    Decode the keypad in the Altera so it "knows" what button is being pushed. Send corresponding information to the display.

    Try working out each part on its own. Try lighting an LED through the Altera for each button pressed. Try getting the display to display anything. Once you can do these then join the two.
     
  3. dag2p

    Thread Starter New Member

    Apr 21, 2009
    2
    0
    Thanks for the reply. The keypad wasn't BCD. It was a matrix style 8 pin design. I have messed around in the lab a bit and figures out a good way to interface the keypad to the up-2. I asked so e friends and they gave me the concept I needed for the kaypad. Now I just need to figure out the LED matrix.

    I understand how the matrix is matrixed out to 14 pins but I don't have a grasp on how to make the matrix show more than 1 LED at a time. I realize that it's not but just refreshing at a rate faster than the eye can see. But what kind of control do I need to do his and how do I interface that control.

    Hate to be a pain on this but it's tough to wrap my head around.
     
  4. StayatHomeElectronics

    Well-Known Member

    Sep 25, 2008
    864
    40
    If the matrix is of the style shown at this link http://www.futurlec.com/LED/LEDM57R.shtml then it is just refreshing at a rate faster than the eye can see.

    The concept here is to turn on row 1 and send out data on the column lines that lights up all the LEDs in that row that you desire. Then, you turn off row one and turn on row 2 and send out data on the column lines that lights up all the LEDs in that row that you desire. Keep going until you get to row 7. Done at a fast enough pace the eye will not notice.

    Let's break it down some more. One thing that you are doing is continuously counting from 1 to 7 to turn the rows on and off, with only one row being on at a time.

    The other part is you are outputing data for each row to generate the desired character. For example, you may want 1 LED on in the first row, 2 in the second and so on. With row 1 active, you would send 10000, where 1 turns on the LED. With row 2 active you would send 11000. Now, you need to decide what output you want, 16 times over for the keypad input.

    You will have a large collection of stored data that you access by the keypad press and which row is being activated.

    I would start by trying to turn on all the LEDs in one row, and then cycle through the rows. Then alter the pattern for the rows. Only then do you try to get the keypad interfaced to the LED matrix. Take it one step at a time

    You can probably drive the LEDs directly from the Altera with some series resistance. I don't the specs on your exact part but be sure not to blow out the LEDs be overdriving them.

    An internet search on "led matrix 5x7" might also get more explanation...
     
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