Use of a PIC

[Edwardo]

Hi Syscoder, your project sounds pretty complex, how did you drive your 20 odd thousand led display?

[ronsimpson]

Edwardo,
Where to start?
30mA x 1500 LEDs = 45 amps!!!! That should light up a room like daylight.
What color of LEDs? We buy 2,000,000 LEDs/year in white + colored LEDs. Most people think LEDs last 10 years. Don’t bet your job on it. Some last a very short time. If you are not clear as to life expectancy then you better do a test. Set up 3 LEDs at 20, 30 and 40mA. Measure light output for the next month. My big white LEDs have serious issues in a week at rated current.

I think your real question is how do I get 1500 outputs from a PIC. You do not need 1500 outputs. Get more outputs:
>Use two ports on your PIC to make a “data bus”. Eight bits for data and 8 bits for control and address. Connect (8 to 64) 74hc373 latches to the data bus and (1 to 8) 74hc138 to the address bus. The 74hc138 looks at A0,1,2 to decide which one of 8 latches to strobe and A3,4,5 to choose which one of 8-74hc138s should respond. You could have 8x8=64 (8 bit ports) or 512 outputs.
>A second method is to use 8 bit shift registers. Your bus is simple. Clock, Data & Load. The shifting will take a while.

Go back and look at the posting on multiplexing LEDs. Made a bank of LEDs that is 200x8. That uses 208 outputs. Each LED is on 1/8th the time at 6 to 8 times the average current. You must get through all 8 banks of LEDs 70 to 100 times per second. Do not drop to 60/second!
Because your display is LARGE, I would break it up into 6 boards of 32x8 LEDs. Each board will have 5 (8 bit) latches or shift registers. (4x8=32 to drive the rows + 8bits to drive the columns) Next you will need some power drivers. The row drivers will have to handle the 150mA or more you send through each LED. The row drivers will control 5 amps.

100%=30mA, 50%=60mA, 25%=120mA 12%=240mA You said the peak current is 150mA so to get full power maybe you can only have 4 columns operating at ¼ duty cycle.

This is toooooo long. Do you need help with software? You should choose a PIC with a large amount of RAM. PIC18Fxxxx
rons