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14 lines
1.1 KiB
Markdown
14 lines
1.1 KiB
Markdown
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## Interface
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We have covered configurations and endpoints but what is an *interface*?
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<p align="center">
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<img src="/usb-interface.svg" alt="TODO">
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<p>
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An interface is closest to a USB device's function. For example, a USB mouse may expose a single HID (Human Interface Device) interface to report user input to the host. USB devices can expose multiple interfaces within a configuration. For example, the nRF52840 Dongle could expose both a CDC ACM interface (AKA virtual serial port) *and* a HID interface; the first interface could be used for (`log::info!`-style) logs; and the second one could provide a RPC (Remote Procedure Call) interface to the host for controlling the nRF52840's radio.
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An interface is made up of one or more *endpoints*. To give an example, a HID interface can use two (interrupt) endpoints, one IN and one OUT, for bidirectional communication with the host. A single endpoint cannot be used by more than one interface with the exception of the special "endpoint 0", which can be (and usually is) shared by all interfaces.
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For detailed information about interfaces check section 9.6.5, Interface, of the USB specification.
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