usb_hid – USB Human Interface Device
The usb_hid module allows you to output data as a HID device.
Available on these boards
- usb_hid.devices: Tuple[Device, Ellipsis]
Tuple of all active HID device interfaces. The default set of devices is
Device.KEYBOARD, Device.MOUSE, Device.CONSUMER_CONTROL, On boards whereusb_hidis disabled by default,devicesis an empty tuple.If a boot device is enabled by
usb_hid.enable(), and the host has requested a boot device, thedevicestuple is replaced whencode.pystarts with a single-element tuple containing aDevicethat describes the boot device chosen (keyboard or mouse). The request for a boot device overrides any other HID devices.
- usb_hid.disable() None
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 asusb_cdcorstorageto free up endpoints for use byusb_hid.
- usb_hid.enable(devices: Sequence[Device] | None, boot_device: int = 0) None
Specify which USB HID devices that will be available. Can be called in
boot.py, before USB is connected.- Parameters:
devices (Sequence) –
Deviceobjects. Ifdevicesis empty, HID is disabled. The order of theDevicesmay 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. Ifboot_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.pyto inform you if not enough endpoints are available.Boot Devices
Boot devices implement a fixed, predefined report descriptor, defined in https://www.usb.org/sites/default/files/hid1_12.pdf, Appendix B. A USB host can request to use the boot device if the USB device says it is available. Usually only a BIOS or other kind of limited-functionality host needs boot keyboard 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
If the host requests the boot keyboard, the report descriptor provided by
Device.KEYBOARDwill be ignored, and the predefined report descriptor will be used. But if the host does not request the boot keyboard, the descriptor provided byDevice.KEYBOARDwill 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.
- usb_hid.get_boot_device() int
- Returns:
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 withboot_device=0, the default, which disables boot device support. If the host did request a boot device, returns the value ofboot_deviceset inusb_hid.enable():1for a boot keyboard, or2for boot mouse. However, the standard devices provided by CircuitPython,Device.KEYBOARDandDevice.MOUSE, describe reports that match the boot device reports, so you don’t need to check this if you are using those devices.- Rtype int:
- usb_hid.set_interface_name(interface_name: str) None
Override HID interface name in the USB Interface Descriptor.
interface_namemust 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.
- class usb_hid.Device(*, report_descriptor: circuitpython_typing.ReadableBuffer, usage_page: int, usage: int, report_ids: Sequence[int], in_report_lengths: Sequence[int], out_report_lengths: Sequence[int])
HID Device specification
Create a description of a USB HID device. The actual device is created when you pass a
Devicetousb_hid.enable().- Parameters:
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_descriptordoes 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 of0for 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 of0for a report that is not an OUT report. “OUT” is with respect to the host.
report_ids,in_report_lengths, andout_report_lengthsmust all have the same number of elements.Here is an example of a
Devicewith 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.- KEYBOARD: Device
Standard keyboard device supporting keycodes 0x00-0xDD, modifiers 0xE-0xE7, and five LED indicators. Uses Report ID 1 for its IN and OUT reports.
- MOUSE: Device
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
Consumer Control device supporting sent values from 1-652, with no rollover. Uses Report ID 3 for its IN report.
- send_report(report: circuitpython_typing.ReadableBuffer, report_id: int | None = None) None
Send an HID report. If the device descriptor specifies zero or one report id’s, you can supply
None(the default) as the value ofreport_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. Thereportitself 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_last_received_report(report_id: int | None = None) bytes | None
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
Noneif nothing received. After returning a report, subsequent calls will returnNoneuntil next report is received.