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geekhack Community => Keyboards => Topic started by: Blaidd Drwg on Tue, 04 December 2018, 17:29:36

Title: Looking for keyboard with a high matrix scan rate
Post by: Blaidd Drwg on Tue, 04 December 2018, 17:29:36

tldr: I'm looking for a keyboard (PS/2, preferably non-mechanical) with a high matrix scan rate to use for a university project.

My team and I are trying to build a setup that allows us to determine when a key was pressed with as much precision as possible. This means reducing the latency between the key press and the registration of the event to a minimum. More specifically, constant latency (e.g. from debouncing) can be easily subtracted afterwards, so what we are really trying to avoid are variations in the latency.

We register keyboard events by connecting to an Arduino via PS/2, so the only big source of latency is the keyboard itself. The variation we've measured in our experiments is very close to what's to be expected from the matrix scan rate (~15 ms for our 75 Hz keyboards, ~10 ms for our 125 Hz keyboard); we're hoping getting a model with a higher scan rate will get us significantly lower than that.

So, do you have any suggestions for us? The keyboard should have a PS/2 connector (to avoid USB polling), not have a distinctive sound (we need it to sound "average", so I'm guessing no mechanicals?), and a low price would be a bonus (we need to justify the expense to our supervisor ;) ).

Title: Re: Looking for keyboard with a high matrix scan rate
Post by: JP on Tue, 04 December 2018, 18:26:13

This might worth looking into. The DMA Common Sense Controller although not a keyboard but a controller for keyboards that use a capacitive pcb such as those found with vintage Model F keyboards. Also this controller implements USB but could possibly be engineered to work over PS/2 instead.
https://deskthority.net/workshop-f7/commonsense-controller-better-capsense-for-the-ibm-type-f-t13988.html?hilit=commonsense
https://deskthority.net/call-for-nominees-f113/best-project-or-innovation-t20153.html

[attachimg=1]

Title: Re: Looking for keyboard with a high matrix scan rate
Post by: Blaidd Drwg on Tue, 04 December 2018, 19:21:35

Looks interesting, and 1 ms latency is less than we would have hoped for! I'll ask the team's tinkerer to take a look at it. Might be a little too time-consuming for us though, we're planning on doing our first experiment in two weeks.