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I am trying to produce keypresses on a typical keyboard matrix circuit with a microcontroller. It's easily done using CD4051BE multiplexers. However, that approach does not allow to produce simultaneous keypresses, also it's sort of bulky.

Now everybody talks of some "crossbar switches" -- a chip that has, say, 8 inputs and 8 outputs and being controlled, say by I2C, can wire any (or many) of them together.

So, I searched and have not found anything like that. Does anyone know of such a chip, please? It would also be great if it's not too rare or exotic.

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    \$\begingroup\$ electronics.stackexchange.com/help/on-topic -- Or maybe you meant you are not looking for a particular model. In either case, I would re-word the question to ensure it cannot be taken to be a shopping question. \$\endgroup\$
    – JYelton
    Commented Jan 6, 2022 at 16:55
  • \$\begingroup\$ Sorry, I meant I am looking for the actual name of the chip. E.g., AD747359H (example). \$\endgroup\$ Commented Jan 6, 2022 at 17:01
  • \$\begingroup\$ I'll edit your question to avoid the shopping vibe - take note. \$\endgroup\$
    – JYelton
    Commented Jan 6, 2022 at 17:04
  • \$\begingroup\$ Try searching for "crosspoint switch" and go through all the datasheets? Beware that some of these ICs do not allow all possible combinations. \$\endgroup\$ Commented Jan 6, 2022 at 17:24
  • \$\begingroup\$ There are. They are called analog switch arrays, have you searched for them? Many chips are rare, expensive, or obsolete these days, so for simple keyboard emulation, these are too high performance to justify the price. With the same price you could take a bunch of 4051 chips and IO expanders to have few simultaneous keys - are there many in addition to shift button? \$\endgroup\$
    – Justme
    Commented Jan 6, 2022 at 17:27

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It's easily done using CD4051BE multiplexers. However, that approach does not allow to produce simultaneous keypresses, also it's sort of bulky.

Well, if the maximum number of simultaneous keypresses is (say) 2 then have two circuit layers of CD4051 multiplexers. Yes, it becomes twice as bulky but, given the chip shortages we have these days (and especially so on rarer items like cross-point switches), it might make some sense to adopt the above approach. I mean, it's not as if this is a saleable item - it sounds like you are wanting to test something and you can probably live with a solution that isn't so streamlined.

It's an option.

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