4 ms·

Seeing this again makes me want to dig out the sketches I had for a FPGA-based keyboard controller. There's no poll latency when nothing is polled! (Okay, okay,

Seeing this again makes me want to dig out the sketches I had for a FPGA-based keyboard controller. There's no poll latency when nothing is polled! (Okay, okay, there's a few clocks.) The trouble with that project was always that I hate prototyping with BGAs, having to deal with carrier boards sucks, and all the QFP or similar FPGAs were limited to 144 pins, which is just not quite enough for 108 keys given the number of other demands for I/Os, and the number of I/Os you actually get on a 144-lead package. I wasn't much looking forward to dealing with the USB either (I seem to remember it would require at least a small softcore?) but at least there's plenty of open or vendor implementations there to "borrow". If anyone wants to rip this off, go right ahead as long as you let me know... this controller was only one piece of a larger idea, and I love it when people do my job for me :)

toast0 5y ago
108 keys sounds like 4 keys too many to me, but I wonder if you could use multiple FPGAs and include a USB hub (soft or real), if you split the ten-key out, that might be enough to do the rest of the keyboard with a 144 pin chip, and the tenkey with a smaller chip.
- exmadscientist 5y ago
  > 108 keys sounds like 4 keys too many to me 108 includes 104 plus 4 media keys. I think there are also a few international layouts with more keys than US-standard, but I never got that far. > I wonder if you could use multiple FPGAs and include a USB hub (soft or real) That... is a recipe for pain. Complexity of small hardware projects is basically Ackermann in the number of processors you are coordinating.... Ideally in a product you really, really want only one firmware blob to update at a time. > if you split the ten-key out, that might be enough to do the rest of the keyboard with a 144 pin chip, and the tenkey with a smaller chip. I don't know if alt-codes would work with this strategy. Regardless, none of this is worth it just to avoid prototyping with a BGA or dev board. (I'm not even trying to avoid those for production; this is my day job so I'm not that afraid of big BGAs. I just don't want to ever have to solder or probe them, and the gods alone save you if you have to rework a joint!)

toast0 5y ago

108 keys sounds like 4 keys too many to me, but I wonder if you could use multiple FPGAs and include a USB hub (soft or real), if you split the ten-key out, that might be enough to do the rest of the keyboard with a 144 pin chip, and the tenkey with a smaller chip.

exmadscientist 5y ago
> 108 keys sounds like 4 keys too many to me 108 includes 104 plus 4 media keys. I think there are also a few international layouts with more keys than US-standard, but I never got that far. > I wonder if you could use multiple FPGAs and include a USB hub (soft or real) That... is a recipe for pain. Complexity of small hardware projects is basically Ackermann in the number of processors you are coordinating.... Ideally in a product you really, really want only one firmware blob to update at a time. > if you split the ten-key out, that might be enough to do the rest of the keyboard with a 144 pin chip, and the tenkey with a smaller chip. I don't know if alt-codes would work with this strategy. Regardless, none of this is worth it just to avoid prototyping with a BGA or dev board. (I'm not even trying to avoid those for production; this is my day job so I'm not that afraid of big BGAs. I just don't want to ever have to solder or probe them, and the gods alone save you if you have to rework a joint!)