Modular Systems Using SPI

[Humberto] is at it again with a NerdKits video detailing the use of an SPI bus to communicate between microcontrollers. He started with a previous LED marquee project which was limited to a 5×24 LED Matrix and developed a modular solution to increase the size limitation.

The writeup and video embedded after the break do a great job of detailing the important differences between a stand-alone and a modular system. The good news is that the ATmega168 chips being used have a built-in interrupt based SPI protocol. Once wired correctly, a master control chip addresses each module separately, adding data to their buffer until a full frame has been transferred, then moves onto the next module.

Some of the caveats to this system such as digital transmission over long distances are discussed. We do wonder about power limitations if all LED’s in the marquee are illuminated at once. But that concern aside, if you’re thinking of playing around with an LED display don’t forget that there’s usually a huge price break for orders of 500 or 1000 LEDs!

5 thoughts on “Modular Systems Using SPI

  1. This is really cool!

    I feel like I2C would be a better choice, though, since it’s able to have an arbitrary number of slaves on only 2 lines. It would definitely make the wiring simple. I think you’d be slightly more limited in clock speed though.

  2. The claim about a limit of 12 submodules is bogus. 4096 is more like it, with the help of a 12 to 4096 line decoder of course (probably better to stick with 3 to 8 line decoders and toss in some 2/3/4/5 input ands down the line).

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