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Topic: Maximum Number of 595's ? (Read 1 time) previous topic - next topic

florinc

Sparkfun (http://www.sparkfun.com/commerce/product_info.php?products_id=760) has an RGB backpack that can be chained. Now the question is "how many can you control from one arduino?".
Their photo shows 7 RGBs linked together.

Mike Mc

#16
May 19, 2009, 06:41 pm Last Edit: May 19, 2009, 07:09 pm by zooto68 Reason: 1
At that price no thanks !! I'd be cheaper with an RGB Matrix each one with it's own Arduino chip controlling it. Could do that for less than $20 each.

So I guess it is looking like each Matrix would need it's own controller chip. With one master chip sending data out along a daisy chained serial line.

Could data be sent out fast enough?

Paul V.

#17
May 19, 2009, 07:32 pm Last Edit: May 19, 2009, 07:37 pm by pvercello Reason: 1
FWIW, the AtXMEGA chips (the next step up from AtMEGA series) support DMA channels, which means you could just ask the DMA controller to pump out your "video buffer" (the LED bit buffer) to the output without using CPU resources (might have to use SPI or a UART for that though).  So your CPU could spend the rest of its time calculating the next frame, etc., rather than having to sit there and pump out bits for the shift-out.

Of course, the XMEGA's run at 32MHz as well, so it might be a moot point, but is something to consider.

-Paul

florinc

I think that the amount of cells (one RGB + one atmega) one can connect to a master uC depends on the application. If you want control over each specific cell, pixel by pixel, that may take more bandwidth than just scrolling a string of characters. In the latter case, each cell could control itself, receiving an "input" character from the previous cell, and sending an "output" character to the next cell. Thus, for this scenario (scrolling text) you could have an unlimited number of cells, each taking care of its own slice of action.

Mike Mc

I was thinking of having each unit have it's own font array, plus an array for sprites. Then the master controller could send simple commands for what character or sprite is to be displayed and where.

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