max7219 yet again

[adumas]

Hi.. A friend of mine helped me out with getting a 7-segment display interfaced with a max7219. The code and circuit work fine.

I'm now trying to expand it's usefulness - I wish to add a temperature input.

So, I thought it would be easy to display the decimal point - but not so.

I've racked my brains and read through the entire forum and can't figure it out.

I'll post the code..

Please let me know what do change..

THanks.

 

[BCJKiwi]

The code would appear to send 4 digits 0 thru 9999. Is this correct?

What do you want to send?

999.9, 99.99, 9999.99 or what?

The logic will need to be changed to insert the '.' into the middle of the data. It would help to see the rest of the program so we could understand how the data arrives at this code block as there may be work to do there as well as here.

 

[LizzieB]

According to the 7219 data sheet "The decimal point is set by bit D7 = 1" so I think that to light the dp on any digit you need to add 128 to the number to be displayed on that digit, so if you send it 1 it will display "1", and if you send it 129, it will display "1.".

 

[adumas]

Perfect - that's just what I needed - I works now...