Anyone working on a MAX7219 8x8 LED matrix display library?

Discuss development of drivers for external hardware and components, such as LCD screens, sensors, motor drivers, etc.
Target audience: Users and developers of drivers.
jgbrown
Posts: 8
Joined: Sun Nov 10, 2019 11:52 pm

Re: Anyone working on a MAX7219 8x8 LED matrix display library?

Post by jgbrown » Thu Oct 01, 2020 7:55 pm

Given the fact that unplugging the display allows the code to continue, I would assume it's a connection issue. The code is trying to establish the SPI interface. Being unable to use reset further supports this condition as the device isn't allowing any further input while is attempting the connection (or failing it by unplugging the LEDs).

What can you share about your device and/or LEDs? Do you have others that you can try to remove the possibility of faulted/shorted parts?

-- Jeff

srihari154
Posts: 2
Joined: Sun Sep 27, 2020 5:46 pm

Re: Anyone working on a MAX7219 8x8 LED matrix display library?

Post by srihari154 » Sat Oct 03, 2020 12:43 pm

Thanks for pointing out jgbrown :)

I ordered a new MAX7219 display and this works perfectly fine with the same set of connections. Not sure exactly where is the connection issue with the old one.

Furthermore I had two questions.

(1) I was having a look at the code you have checked in, The marquee function really useful. But I wanted to modify this have vertical scrolling too. Is this doable? I wanted to scroll for each second of the time(clock) to display the transition of seconds.
(2) I have tried various micropython libraries available for the display and How much ever I try, the last row(8) of led`s is never illuminated or used to display the numbers or alphabets or texts(only 7 rows are used), Am I missing something here?

Regards
Srihari

jgbrown
Posts: 8
Joined: Sun Nov 10, 2019 11:52 pm

Re: Anyone working on a MAX7219 8x8 LED matrix display library?

Post by jgbrown » Thu Oct 08, 2020 12:55 am

Hi -- Glad you figure the connection issue out. There is a possibility that at some point the connection was wrong and it fried something on the LEDs. I've overpowered some and they don't like it! :-)

Vertical Scrolling: I'm sure it's possible but I've never really dug into it. I unfortunately don't have time to spend right now, but if you suspect you would need to modify the show() function to view input row by row rather than column by column. If your or anyone else comes up with a solution, I would be happy to work it into my code...

8th Row: In my simple terms, the character set only requires seven bits so the eighth bit (row) goes unused. I've seen different applications that allow you to adjust which row not to use (1st or 8th) but have never had a need for such functionality. It may be possible to develop your own character set that utilizes all 8 bits but that too is beyond my knowledge level.

Enjoy!

-- Jeff

Post Reply