I'm assuming you'll use RGB LEDs like this one: http://www.sparkfun.com/commerce/product_info.php?products_id=105
It has 4 legs, one is common and the other 3 are for red, green and blue. So it's effectively 3 LEDs in one package. If you want red, you turn on the red and turn off green & blue. Same for G or B. Magenta is R+B, Cyan is G+B, white is R+G+B, and so on.
yes, I understand.
additive color building.
With the MAX7219 you can turn individual LEDs on or off. Or you can vary the brightness of all of them at the same time. You wouldn't be able to vary the brightness of individual LEDs (unless you went for the the expensive BlinkM option).
Changing from red to blue just means turning off the red LED and turning on the blue one - which is controlled by a separate 7219. So you would have to send commands to each chip.
Blinking LEDs would be done by turning them off and on in the arduino's software, using its timing functions.
If I understand correctly, I have to "build" functions in Wiring AND in Max/MSP in order to make a "protocol"
I mean "own protocol"= I send 001000 from max, The board understand led1off..... ledn On etc
You haven't said what configuration your LEDs will be in, but since there are 50 I'm assuming it's not a matrix. (the 7219 often drives an 8x8 matrix.)
Nevertheless you might find it helpful to represent the LEDs in each display as binary numbers, where a 0 in the number means off and 1 means on. This is known as a bitmap. You could have 3 x 50-bit binary numbers to represent your whole display. Since 50 bits takes up 4 bytes anyway, in practice you would have 3 x 64-bit numbers, which you can send from Max/MSP to the arduino through Max's serial object. Then read in the numbers on the arduino using Serial.read() and send the relevant commands to the 7219.
I understand these concepts.
The project can be that:
I could remove the last line. not sure.
btw, there is a matrix of 8x6 (or 8x5 as I wrote above)
the other leds should receive other kind of information.
But I guess they may be involved in the same matrix for easiest process.
the source of led information will be make in Max/MSP. (I guess... ?!)
Hope this is starting to make sense!
it definitively starts to make sense!
I have to thank you very much.
But......... as usual in this kind of question, I have other questions ....
How could I chain my 3 (or more) MAX7219 ???
I'll buy very soon all the parts (+ 3 or 4 breadboard to prototype that...)