usb_hid – USB Human Interface Device
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 where
usb_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, the
devicestuple is replaced when
code.pystarts with a single-element tuple containing a
Devicethat 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 as
storageto free up endpoints for use by
- 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.
devices (Sequence) –
devicesis empty, HID is disabled. The order of the
Devicesmay 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.pyto inform you if not enough endpoints are available.
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 by
Device.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
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
1for a boot keyboard, or
2for boot mouse. However, the standard devices provided by CircuitPython,
Device.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:
- 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
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
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
0for 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
0for a report that is not an OUT report. “OUT” is with respect to the host.
out_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), )
- 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.
- usage_page: int
The device usage page identifier, which designates a category of device. (read-only)
- usage: int
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.
- 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 of
report_id. Otherwise you must specify which report id to use when sending the report.
- 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 return
Noneuntil next report is received.