Shop OBEX P1 Docs P2 Docs Learn Events
max7219 assist — Parallax Forums

max7219 assist

nick bernardnick bernard Posts: 329
edited 2004-10-27 13:17 in BASIC Stamp
hail,

this is bugging me to the max!
i have devised a crude prototype with a max7219 connected to a 8X8 led array. the module is controlled by a bs2p on a nx1000

when ever i try to light up·row 1 or 2 on the matrix (the equivalent to displaying a 8 +dp on a 7-seg) the module· goes dark and stops working for any future commands. the stamp continues to shift data.

any help would be well received

rox on
nick bernard

·

Comments

  • Jon WilliamsJon Williams Posts: 6,491
    edited 2004-10-20 17:26
    You need to make sure that you're activating all eight digits and that they are set to bit mode. This will let you map the LEDs any way you want.

    ▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔
    Jon Williams
    Applications Engineer, Parallax
    Dallas Office
  • KenMKenM Posts: 657
    edited 2004-10-20 20:09
    http://forums.parallax.com/showthread.php?p=464324
  • nick bernardnick bernard Posts: 329
    edited 2004-10-25 16:51
    HAIL,

    my code works fine so does KenMs

    i think that there is a problem with my circuit that is causing the fault i just dont understand why the 7219 stops accepting commands after the fault, which occurs when i write a 255 to the·1st·or·2nd·digit.

    if there was a problem with the led matrix then why would it work fine counting up to 254 on every digit but fail at 255 on the first and second digit,

    is there an exception in the max7219 that shuts the chip down in over current situations or something?
  • KenMKenM Posts: 657
    edited 2004-10-25 19:52
    Can you post the lines of code where you write 255 to the 7219?
  • nick bernardnick bernard Posts: 329
    edited 2004-10-25 21:22
    Main:
    DO
    FOR digit = 1 TO 8
    FOR value = 0 TO 250
    PAUSE 5
    GOSUB row
    NEXT
    NEXT
    LOOP

    Row:
    SHIFTOUT DAT,CLK,MSBFIRST,[noparse][[/noparse]digit,value]
    PULSOUT LOAD,1
    RETURN
  • nick bernardnick bernard Posts: 329
    edited 2004-10-25 21:23
    HAIL,
    if the current draw was to much for the nx-1000's 5v reg could that lock the system
    rox on
    nick bernard
  • Chris SavageChris Savage Parallax Engineering Posts: 14,406
    edited 2004-10-26 14:16
    Nick,

    ·· Is the NX's regulator getting excessively hot?· Can you touch it?· If so it shouldn't be overheating...Besides, there really isn't that much of a difference in the current draw from 254 to 255...I mean close to the same number of LEDs should be lit.· It's not like an 8, where the most are lit...I would think all 8's across the board would be more likely to do something like that.



    ▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔
    Chris Savage

    Knight Designs
    324 West Main Street
    P.O. Box 97
    Montour Falls, NY 14865
    (607) 535-6777

    Business Page:·· http://www.knightdesigns.com
    Personal Page:··· http://www.lightlink.com/dream/chris
    Designs Page:··· http://www.lightlink.com/dream/designs
    ·
  • nick bernardnick bernard Posts: 329
    edited 2004-10-26 18:29
    hail chris!

    i can now count all registers up to 255; nothing has changed, honestly. However the 8X8 matrix will go dark if i up the intensity past 2. also there is a definate relation between the intensity and the number of led's lit at the time of the fault. (higher intensity : fewer digits)

    i can also count all registers up to 254 with higher intensity, it does freeze at max (15) though

    the more i think about it the more it seems like a current problem that will drop the supply voltage enough to interrupt the data flow but not to reset the stamp (i set up a debug to test that case).

    rox on
    nick bernard
  • Chris SavageChris Savage Parallax Engineering Posts: 14,406
    edited 2004-10-26 21:23
    So it's working now, or it isn't?· You got me on that one!· blush.gif

    ▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔
    Chris Savage

    Knight Designs
    324 West Main Street
    P.O. Box 97
    Montour Falls, NY 14865
    (607) 535-6777

    Business Page:·· http://www.knightdesigns.com
    Personal Page:··· http://www.lightlink.com/dream/chris
    Designs Page:··· http://www.lightlink.com/dream/designs
    ·
  • nick bernardnick bernard Posts: 329
    edited 2004-10-26 21:58
    works fine on intensity < 3

    if i set the intensity to 15 then the following

    FOR digit = 8 TO 1
    FOR value = 0 TO 255 ' the ic locks up after digit = 1 value = 255
    PAUSE 5
    GOSUB row
    NEXT
    NEXT


    FOR digit = 1 TO 8
    FOR value = 0 TO 255 ' the ic locks up after digit = 1 value = 255
    PAUSE 5
    GOSUB row
    NEXT
    NEXT


    the current resistor is 10k on the max7219 btw

    rox on
    nick bernard
  • Chris SavageChris Savage Parallax Engineering Posts: 14,406
    edited 2004-10-27 01:51
    Well Nick,

    ·· I'm glad you got it figured out based on input back to you...· wink.gif·· I have been meaning to play with the MAX7219, but have to free a breadboard to mount my displays on (Which are rather large).



    ▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔
    Chris Savage

    Knight Designs
    324 West Main Street
    P.O. Box 97
    Montour Falls, NY 14865
    (607) 535-6777

    Business Page:·· http://www.knightdesigns.com
    Personal Page:··· http://www.lightlink.com/dream/chris
    Designs Page:··· http://www.lightlink.com/dream/designs
    ·
  • KenMKenM Posts: 657
    edited 2004-10-27 02:24
    Nick,

    On my set up I used a 47k ohms for the current resistor of the 7219.

    With that resistor, I had no problem with intensity settings up to $A (did not go past $A)

    fyi
  • nick bernardnick bernard Posts: 329
    edited 2004-10-27 13:17
    HAIL KenM,

    i switched to a 47k current resistor and now the beast works fine fine like muscadine wine.

    thx to all for the assist

    rox on

    nick bernard
Sign In or Register to comment.