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PS/2 things (lemmy.world)

submitted 1 month ago* (last edited 1 month ago) by carrylex to c/[email protected]

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In todays edition of "stuff that I found in my storage" a PS/2 meme

Image transcription:

mov rax, rbx add rax, rcx HELLO IT'S THE KEYBOARD I HAVE AN IMPORTANT MESSAGE E

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[–] InverseParallax 6 points 1 month ago* (last edited 1 month ago) (1 children)

Actually it's both, there's polling with a timeout interrupt if an incoming urb hasn't been processed quickly.

https://crlab.ece.ucr.edu/usbgps/ohci_uhci.html

This way you can take them in batches at regular intervals.

[–] Aceticon 4 points 1 month ago

It makes sense given that even microcontrollers (which are a lot simpler than microprocessors) have dedicated hardware doing the send/receive part of the work which is independent of the processing core and will only fire interrupts if the send or receive buffers reach an empty state.

This way of doing things was already usual before USB for things like I2C, Serial and SPI and whilst the USB protocol is significantly more complex, the same kind of design was also used for it.