usb_hid – USB Human Interface Device
The usb_hid module allows you to output data as a HID device.
Tuple of all active HID device interfaces. The default set of devices is Device.KEYBOARD, Device.MOUSE, Device.CONSUMER_CONTROL, On boards where usb_hid is disabled by default, devices is an empty tuple.
If a boot device is enabled by usb_hid.enable(), and the host has requested a boot device, the devices tuple is replaced when code.py starts with a single-element tuple containing a Device that describes the boot device chosen (keyboard or mouse). The request for a boot device overrides any other HID devices.
Do not present any USB HID devices to the host computer. Can be called in boot.py, before USB is connected. The HID composite device is normally enabled by default, but on some boards with limited endpoints, including STM32F4, it is disabled by default. You must turn off another USB device such as usb_cdc or storage to free up endpoints for use by usb_hid.
Specify which USB HID devices that will be available. Can be called in boot.py, before USB is connected.
devices (Sequence) – Device objects. If devices is empty, HID is disabled. The order of the Devices may matter to the host. For instance, for MacOS, put the mouse device before any Gamepad or Digitizer HID device or else it will not work.
boot_device (int) – If non-zero, inform the host that support for a a boot HID device is available. If boot_device=1, a boot keyboard is available. If boot_device=2, a boot mouse is available. No other values are allowed. See below.
If you enable too many devices at once, you will run out of USB endpoints. The number of available endpoints varies by microcontroller. CircuitPython will go into safe mode after running boot.py to inform you if not enough endpoints are available.
Boot Devices
A USB HID boot device implements a fixed, predefined report descriptor, as defined in https://www.usb.org/sites/default/files/hid1_12.pdf, Appendix B. Currently the only HID boot devices defined in the USB specification are a keyboard and a mouse. A USB host can ask a USB device to use a boot device if the USB device says it is available. Usually only a limited-functionality host like a BIOS or other boot-time software needs boot device support.
For example, to make a boot keyboard available, you can use this code:
usb_hid.enable((Device.KEYBOARD,), boot_device=1) # 1 for a keyboard, 2 for a mouse
If the host requests the boot keyboard, the report descriptor provided by Device.KEYBOARD will be ignored, and the predefined report descriptor will be used. But if the host does not request the boot keyboard, the descriptor provided by Device.KEYBOARD will be used.
The HID boot device must usually be the first or only device presented by CircuitPython. The HID device will be USB interface number 0. To make sure it is the first device, disable other USB devices, including CDC and MSC (CIRCUITPY). If you specify a non-zero boot_device, and it is not the first device, CircuitPython will enter safe mode to report this error.
the boot device requested by the host, if any. Returns 0 if the host did not request a boot device, or if usb_hid.enable() was called with boot_device=0, the default, which disables boot device support. If the host did request a boot device, returns the value of boot_device set in usb_hid.enable(): 1 for a boot keyboard, or 2 for boot mouse. However, the standard devices provided by CircuitPython, Device.KEYBOARD and Device.MOUSE, describe reports that match the boot device reports, so you don’t need to check this if you are using those devices.
Override HID interface name in the USB Interface Descriptor.
interface_name must be an ASCII string (or buffer) of at most 126.
This method must be called in boot.py to have any effect.
Not available on boards without native USB support.
HID Device specification
Create a description of a USB HID device. The actual device is created when you pass a Device to usb_hid.enable().
report_descriptor (ReadableBuffer) – The USB HID Report descriptor bytes. The descriptor is not not verified for correctness; it is up to you to make sure it is not malformed.
usage_page (int) – The Usage Page value from the descriptor. Must match what is in the descriptor.
usage (int) – The Usage value from the descriptor. Must match what is in the descriptor.
report_ids (Sequence[int]) – Sequence of report ids used by the descriptor. If the report_descriptor does not specify any report IDs, use (0,).
in_report_lengths (Sequence[int]) – Sequence of sizes in bytes of the HID reports sent to the host. The sizes are in order of the report_ids. Use a size of 0 for a report that is not an IN report. “IN” is with respect to the host.
out_report_lengths (int) – Sequence of sizes in bytes of the HID reports received from the host. The sizes are in order of the report_ids. Use a size of 0 for a report that is not an OUT report. “OUT” is with respect to the host.
report_ids, in_report_lengths, and out_report_lengths must all have the same number of elements.
Here is an example of a Device with a descriptor that specifies two report IDs, 3 and 4. Report ID 3 sends an IN report of length 5, and receives an OUT report of length 6. Report ID 4 sends an IN report of length 2, and does not receive an OUT report:
device = usb_hid.Device(
descriptor=b"...", # Omitted for brevity.
report_ids=(3, 4),
in_report_lengths=(5, 2),
out_report_lengths=(6, 0),
)
The HID device is able to wake up a suspended (sleeping) host computer. See send_report() for details.
Standard keyboard device supporting keycodes 0x00-0xDD, modifiers 0xE-0xE7, and five LED indicators. Uses Report ID 1 for its IN and OUT reports.
Standard mouse device supporting five mouse buttons, X and Y relative movements from -127 to 127 in each report, and a relative mouse wheel change from -127 to 127 in each report. Uses Report ID 2 for its IN report.
Consumer Control device supporting sent values from 1-652, with no rollover. Uses Report ID 3 for its IN report.
Send an HID report. If the device descriptor specifies zero or one report id’s, you can supply None (the default) as the value of report_id. Otherwise you must specify which report id to use when sending the report.
If the USB host is suspended (sleeping), then send_report() will request that the host wake up. The report itself will be discarded, to prevent unwanted extraneous characters, mouse clicks, etc.
Note: Host operating systems allow enabling and disabling specific devices and kinds of devices to do wakeup. The defaults are different for different operating systems. For instance, on Linux, only the primary keyboard may be enabled. In addition, there may be USB wakeup settings in the host computer BIOS/UEFI.
Get the last received HID OUT or feature report for the given report ID. The report ID may be omitted if there is no report ID, or only one report ID. Return None if nothing received. After returning a report, subsequent calls will return None until next report is received.
The device usage page identifier, which designates a category of device. (read-only)
The device usage identifier, which designates a specific kind of device. (read-only)
For example, Keyboard is 0x06 within the generic desktop usage page 0x01. Mouse is 0x02 within the same usage page.
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