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I'm trying to connect this 50-pin e-ink display to an Atmel ATmega328p for a hobby project.

The biggest design challenge I'm facing is connecting all the pins from the display to the MCU in an orderly way. Originally I was using six 8-bit serial to parallel decoder / shift registers (e.g., 74HC595, chaining them together) then connecting the 2 leftover pins to the MCU directly. But this approach is a mess on the breadboard.

Is there any way to get a wider shift register (e.g., 32-bit or 64-bit) to make things better? Or is there another type of (inexpensive) chip entirely that would work? I've looked at LED drivers, but thought it has too many special features for this application.

Thanks in advance!

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You can cascade shift registers to get a big shift register. The 74HC595 has the Q7S pin for that.

schematic

simulate this circuit – Schematic created using CircuitLab

Add as many Shift Registers to the chain as you like.

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  • \$\begingroup\$ Definitely, good idea. That's what I'm doing right now, but that still requires each shift register to have 5 of its own wires, which quickly scale up. I'd prefer to just have 5 wires going to a chip, which then takes care of outputting the 50 pins all in one, monolithic solution. \$\endgroup\$ – mr_schlomo Apr 20 '15 at 19:09
  • \$\begingroup\$ No, if you cascade the 595's only 3 wires are required: clock, data out and latch (cs). \$\endgroup\$ – Alexxx Apr 20 '15 at 19:14
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    \$\begingroup\$ You might like to give a little more information on how this would work to clear things up. \$\endgroup\$ – David Apr 20 '15 at 19:37
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If you want a single chip solution you could buy a CPLD with enough IO pins and program it to work as a shift register. They aren't even expensive these days and for simple tasks like this you may even get away without learning a HDL language like verilog or vhdl.

For breadboarding you would need some kind of DIY friendly breakout board, and if you do so you could just as well make a custom board, put your three 595's and a proper connector of your e-ink display onto it.

Otoh if you go the CPLD route, once you've learned how to use them you'll never have to buy and connect individual logic chips for prototyping anymore.

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The part what you need is called "port expander" or "I/O expander". Try to google it.The biggest one I've found is 60 bit.

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