MAX 7219 decoding on - off

Mikael S

I have a project that are going to show the temperature and time on a very big LED-display.
But i have a last problem with this, i use a MAX 7219 for driving the displays and i need to display the temperature with the degree "ring" after.
To do this i guess that i first must have the decoding mode on to decode the temperature, and the switch of the decode for the ring. But i can't just dont figure out how?!

Would be very thankful for any help or tip i can get!

Thanks,

Mikael

Chris Savage

Mikael,

You’re correct, you have to display each digit with decode on, and then the symbol (degrees) with decode off and then send the correct pattern to light up the segments for the symbol. Turning off the decode mode is pretty straight forward. If the display will always have the same layout (always the same digits decoded/not decoded) then you can just set this at the beginning of your program.

SHIFTOUT DataIO, Clock, MSBFIRST, [noparse][[/noparse]$09, %11111111]

Just replace one of the binary 1’s in the example above with a 0 in the position of the digit you want to disabling decoding on. The others will remain in decode mode. I hope this helps. Take care.

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Chris Savage
Parallax Tech Support

Mikael S

Thank you for your repy!

I forgot to tell that, the display will shift between time and temperature. So i must shift the decode mode on and off all the time.



Micke

Chris Savage

No problem…Just insert that code in between where the routines switch and set the bits as you need them for a particular routine and you should be set. Take care.

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Chris Savage
Parallax Tech Support