circuitpython raw hid demo

rawhid_code.py

# rawhid_code.py  -- copy to CIRCUITPY as "code.py"
# don't forget to install rawhid_boot.py as "boot.py" and press reset
# works with report IDs up to 63 byte report count
# test with hidapitester like:
# ./hidapitester --usagePage 0xff00 --usage 1 --open -l 64 --send-output 2,3,4,5 --timeout 1000 --read-input 1
# adapted from code presented here:
# https://github.com/libusb/hidapi/issues/478

import time
import usb_hid
import adafruit_hid

raw_hid = adafruit_hid.find_device(usb_hid.devices, usage_page=0xff00, usage=0x01)

print("raw_hid: %04x %04x" % (raw_hid.usage_page, raw_hid.usage) )

while True:
    out_report = raw_hid.get_last_received_report(2) # out from computer
    if out_report:
        print("len:",len(out_report),["%02x" % x for x in out_report])
        time.sleep(0.5)
        print("sending copy on reportid 1")
        in_report = bytearray(out_report)  # copy in case we want to modify
        raw_hid.send_report(in_report, 1);  # in to computer

~rawhid_boot.py

# rawhid_boot.py --
# any changes here only reflected after board reset

import usb_hid

REPORT_COUNT = 63  # size of report in bytes

CUSTOM_REPORT_DESCRIPTOR = bytes((
    0x06, 0x00, 0xff,  # Usage page (Vendor Defined Page1)
    0x09, 0x01,        # Usage (Vendor Page 1)
    0xA1, 0x01,        # Collection (Application)

    0x85, 0x01,        # Report ID (1)
    0x09, 0x00,        # Usage Page (Undefined)
    0x15, 0x00,        # Logical Minimum (0)
    0x26, 0xFF, 0x00,  # Logical Maximum (255)
    0x75, 0x08,        # Report Size (8 bits)
    0x95, REPORT_COUNT, # Report Count (64 fields)
    0x82, 0x02, 0x01,  # Input (Data,Var,Abs,Buf)

    0x85, 0x02,        # Report ID (2)
    0x09, 0x00,        # Usage (Undefined)
    0x09, 0x00,        # Usage Page (Undefined)
    0x15, 0x00,        # Logical Minimum (0)
    0x26, 0xFF, 0x00,  # Logical Maximum (255)
    0x75, 0x08,        # Report Size (8 bits)
    0x95, REPORT_COUNT, # Report Count (64 fields)
    0x92, 0x02, 0x01,  # Output (Data,Var,Abs,Buf)

    0xC0,        # End Collection
))

raw_hid = usb_hid.Device(
    report_descriptor=CUSTOM_REPORT_DESCRIPTOR,
    usage_page=0xff00,         # Vendor defined
    usage=0x01,                # Vendor page 1
    report_ids=(1, 2),
    in_report_lengths=(REPORT_COUNT,0),
    out_report_lengths=(0, REPORT_COUNT),
)

usb_hid.enable( (raw_hid,) )

Is this duplicated line needed?

    0x09, 0x00,        # Usage (Undefined)
    0x09, 0x00,        # Usage Page (Undefined)

Trying to understand how to write the simplest two-way custom HID device. Thanks for sharing this! Very useful.

Hi @dtcooper,
It's unclear to me. Since it's all in the same Collection, I think most items apply as soon as they're stated. So I think you may be correct. But I've never tested it.

Appears to be broken in CircuitPython 9.1.0-beta.3 for at least the Raspberry Pi Pico. Workaround is use CircuitPython 9.1.0-beta.2.

Noting this for anyone that might find this info useful! See related issue: adafruit/circuitpython#9306

Cheers