Matrix lib/MAX7219 wrong ouput?

Forum 2005-2010 (read only) Hardware Interfacing
1

Hi,

I've just received my samples from Maxim and have been playing around. At first I thought a bunch of the chips were damaged as I have only connected 8 LEDS and none of them were turning on. I checked through several tutorials for the matrix library and checked all my connections. however nothing turned on. Then I though well lets play around a little and turn one out of 8 leds on from each of the 8 outputs. Low and behold an LED turns on. However it was the wrong one. On futher examination -everything is backwards. The array is [0-7][0-7] if you use row 0 then row 7 actually turns on, same with the individual LED's the 0 output turns on led 7. And yes I've checked everything over and over, so either the library is backwards, or the datasheet is backwards, take your pick. Just thought I'd ask if anyone else has come across this little slip up and if there is a decent work around besides wiring everything in reverse.

Justin

2

There was some controversy about "which way is up"!
There is also confusion about the roll that the DP (decimal point) line played.

Based on the this, I think you will find that the Matrix lib and another - the LedControl lib - treat the issue differently.

Therefore, you might want to try the LedControl lib, and see how that works.
(You'll find it, and other info in the Playground | Output | LEDs| MAX72xx)

3

Thanks I'll give the other library a go. I'll report back sometime this weekend :slight_smile:

4

Thank you Thank you Thank you :slight_smile:

the LedControl Library does exactly what I need, and has everything around the way I would expect.