Using 2 lines of MAX7219 LED matrix

Using Arduino Programming Questions
1

Hi all

I want to create a display that shows time from a GPS sync’d RTC on the top line of an 8 LED matrix display and the second line also an 8 LED matrix long to be a scrolling message board.

IMG_9579

Have already done a one line clock project. Want to combine both and put clock on top line.

When using two lines of LED matrix display for separate information is it better/easier to program for two 8 line displays and run them off different data pins as independent lines?

Or is it possible/better/easier in the MAX7219 display to run it as 16 characters and print the clock information to matrix 1-8 & the message information to matrix 9-16?

Thanks

Dave

2

You can make daisy chain operation of two matrix modules by connecting the DOUT-pin of one Module with DIN-pin of the second Module.

3

@dkjonesau
Actually I think it will be a matter of personal preference.
For me, the software will be simpler if you treat them as 2 separate displays.
Cascading the ICs only saves you one pin.

4

Thanks for replying Jim. This was the way I was originally thinking it would go.

I assume I define the second display pins and then somehow establish it as a second display to write to.

Bit of a learning curve ahead.

Any suggestions welcome

DJ

5

The clock (CLK) and data (DIN) pins can be shared. You only need separate LOAD signals so you can select which IC get the data you just sent.
Then basically the code will be identical for both displays

6

I’ll start by seeing if I can get the message working on both then develop from there I think.

Thanks. I’m sure there will be more questions. Great community.

DJ

7

Good plan.
Many people will try doing the whole at once and then become hopelessly lost in their own code.

8

There are two approches for the solution of a problem:
Top Down and
Bottom UP

Both approaches work equally for a careful/experienced worker; however, SSS Methdology is better for trouble shooting of hardware and debugging of software..

9

If the update rate of the 2 lines is different it would be faster to treat it as 2 separate lines. You would not be writing unchanging data to the line with the slower update rate.

10

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