MAX7219 + LED Matrix Wiring?

[PaulRB]

marco_c:
Are you sure that you are mapping the DP (decimal point) output signal from the IC to the right column or row?

I think Marco nailed it there.

Look at the sequence the above page from the data sheet: left-to-right it's DP, A, B, C, D, E, F, G

Not: A, B, C, D, E, F, G, DP, as I think you numbered them.

row     led pin     chip pin
1         9         14 SEG A
2        14         16 SEG B
3         8         20 SEGC
4        12         23 SEG D
5         1         21 SEG E
6         7         15 SEG F
7         2         17 SEG G
8         5         22 SEG DP

[thehardwareman]

PaulRB:
I think Marco nailed it there.

Look at the sequence the above page from the data sheet: left-to-right it's DP, A, B, C, D, E, F, G

Not: A, B, C, D, E, F, G, DP, as I think you numbered them.

No, I'm not sure - I just tried to use the LedControl library. Guess the mapping is done inside the library? So if the mapping is incorrect it must be in the library?

And I was following the pin connection table given in this thread some time ago. Is that table correct?

[PaulRB]

Guess the mapping is done inside the library?

No, it's done inside the chip. The library is not re-mapping anything.

So try this:

row     led pin     chip pin
1         9         22 SEG DP
2        14         14 SEG A
3         8         16 SEG B
4        12         20 SEG C
5         1         23 SEG D
6         7         21 SEG E
7         2         15 SEG F
8         5         17 SEG G

[PaulRB]

Genesis92:
row display pin MAX7219 pin
1 9 14
2 14 16
3 8 20
4 12 23
5 1 21
6 7 15
7 2 17
8 5 22

Yes, that might be wrong. Try my suggestion and we'll know for sure.

[thehardwareman]

I'm about to do that because I realized that the table given in reply #1 is wrong. The one above is probably correct (just wrote down the new sequence before reading your reply).

Guess the lesson learned this time is - not trust everything you read on Internet (surprised?? ;))

[thehardwareman]

PaulRB:
Yes, that might be wrong. Try my suggestion and we'll know for sure.

The first table was incorrect and your suggestion was correct. Thanks

Wonder why the first able has not been questioned?

[PaulRB]

thehardwareman:
The first table was incorrect and your suggestion was correct. Thanks

Thanks for feeding back. +1 Karma

thehardwareman:
Wonder why the first able has not been questioned?

It was a pretty subtle error for anyone to have spotted in that long and detailed reply. But I would expect someone to have tried it and found the error over the last 6 years!