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Max7219 display - help — Parallax Forums

Max7219 display - help

VonSzarvasVonSzarvas Posts: 2,393
edited 2021-04-06 04:06 in General Discussion

We have a customer that asked about using the Max7219 display with the Parallax Propeller P1.

When the unit is turned on all 64 leds lock on to max brightness .. no codes sent to the unit dislodge this .. the only way to reset it is to disconnect vcc

I don't one of these modules yet.... is there anyone that has tried this module ?
Any advice on how it should behave ?

Thank you !!

Edit: microcontroller was originally stated as P2, whereas the customer is working with the P1.


  • JonnyMacJonnyMac Posts: 7,618

    In my experience the MAX7219 is pretty well behaved. They could try a pull-up on the CS pin to keep things quiet. Should also check initialization code, because proper coms to the device should allow the display to be cleared. I've attached my simple P2 object that was used in the online class I did a couple months ago.

  • @JonnyMac .. I had done the pull up on the cs pin with no success .. I'm still a P1 spin programmer so your P2 object example was a bit of a challenge .. but I got it ..
    I had not used the initializing led test " turn on all the leds " code .. when you do use that code you follow it with " turn them off " .. I added that to my initializing
    code and all seems to be working now .. THANK YOU VERY MUCH FOR YOUR TIME .. stopwatch in Minnesota

  • JonnyMacJonnyMac Posts: 7,618

    I'm glad you got it working. I do have a P1 version of that driver if you want it.

  • Thanks Jon- and apologies for having assumed the wrong uC.

    P1 code... yes please! That would be great. I should update this thread title appropriately!

  • Loose pin connections, and low voltage will make it go into test mode also, all output on and max brightness

  • @JonnyMac Hi, Jonny, do you have a P1 version of that driver in C ? If you have, I would like to have a copy. Thanks.

  • @JonnyMac Hi, Jon: I was so exciting when I read your post and didn't pay attention to the small print. Sorry about that.

  • JonnyMacJonnyMac Posts: 7,618

    @youngfeng said:
    @JonnyMac Hi, Jonny, do you have a P1 version of that driver in C ? If you have, I would like to have a copy. Thanks.

    No. I don't write [much] C for the Propeller; I'm a big fan of Spin. You can find lots of C code for the MAX7219 for other processors that shouldn't be hard to modify for the Propeller. You'll have to bit-bang the SPI portion, but that's really easy on the Propeller in any language.

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