how many keys for custom HID descriptor?
Posted: 29 Jul 2015, 22:48
Hi everyone,
I've been working on a sim project recently that involves wiring a ton of switches and buttons into a PC. Initially we were using keyboard encoders but the number of buttons quickly grew beyond what (i think?) we can handle with a keyboard.
If I built my own keyboard using the HID interface, and assigned a key to every possible scan code, and wrote a program to interpret those, then what would be the absolute maximum possible number of keys? (I've been researching this question for a couple weeks now and become thoroughly confused by the scan codes, HID Report Descriptors, etc.)
If the answer is "a whole butt-load of them"... then.... how is that? Has someone done this?
If the answer is "256, or what's defined in the HID usage tables"... then... why do we still use HID?
Imagine a completely custom keyboard with a mode switch. One side of the switch is HID, so you can use the keyboard in BIOS and other good places. The other side of the switch makes the keyboard act like a serial device and connects to a custom C program (once it's booted and running). Now you can do whatever you want, like having an individual key for the thousand-or-so most used kanji ideographs (image search gives good examples of this). A mode might switch to a greek layout, unicode smiley faces, etc. These are just examples.
I don't want to argue about the usability, application, or practicality of this type of keyboard. I'm just trying to fully understand the limitations of the HID interface.
Thanks
flynx
I've been working on a sim project recently that involves wiring a ton of switches and buttons into a PC. Initially we were using keyboard encoders but the number of buttons quickly grew beyond what (i think?) we can handle with a keyboard.
If I built my own keyboard using the HID interface, and assigned a key to every possible scan code, and wrote a program to interpret those, then what would be the absolute maximum possible number of keys? (I've been researching this question for a couple weeks now and become thoroughly confused by the scan codes, HID Report Descriptors, etc.)
If the answer is "a whole butt-load of them"... then.... how is that? Has someone done this?
If the answer is "256, or what's defined in the HID usage tables"... then... why do we still use HID?
Imagine a completely custom keyboard with a mode switch. One side of the switch is HID, so you can use the keyboard in BIOS and other good places. The other side of the switch makes the keyboard act like a serial device and connects to a custom C program (once it's booted and running). Now you can do whatever you want, like having an individual key for the thousand-or-so most used kanji ideographs (image search gives good examples of this). A mode might switch to a greek layout, unicode smiley faces, etc. These are just examples.
I don't want to argue about the usability, application, or practicality of this type of keyboard. I'm just trying to fully understand the limitations of the HID interface.
Thanks
flynx