usb-device-cdc: Fix default timeout in CDCInterface.init().#1080
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Jul 11, 2026
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This fix looks correct.
The reason it works with the provided CDC example (examples/device/cdc_repl_example.py) is because that example does:
cdc = CDCInterface()
cdc.init(timeout=0) # zero timeout makes this non-blocking, suitable for os.dupterm()
CDCInterface.__init__() sets self._timeout = 1000, then calls self.init(**kwargs). The init() method had timeout=None as default, which unconditionally overwrites self._timeout with None. This causes TypeError in read(), write(), readinto(), and ioctl() which all compare int >= self._timeout. Set the default timeout=1000 in init() to match the intended default, consistent with how other parameters (baudrate, bits, etc.) have their defaults specified directly in the init() signature. Signed-off-by: Andrew Leech <andrew.leech@planetinnovation.com.au>
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Summary
CDCInterfaceis broken when constructed with default arguments — callingread(),write(),readinto(), orflush()raisesTypeError: unsupported types for __ge__: 'int', 'NoneType'becauseself._timeoutends up asNone.__init__setsself._timeout = 1000then immediately callsself.init(**kwargs). Theinit()method hastimeout=Noneas default and unconditionally assignsself._timeout = timeout, overwriting the 1000 with None. All the stream methods then fail ontime.ticks_diff(...) >= self._timeout.Fix is changing the default parameter from
timeout=Nonetotimeout=1000, consistent with how the other init parameters (baudrate, bits, parity, stop) all carry their real defaults in the signature.Testing
Tested on ESP32-S3 as USB CDC device with an MIMXRT1170-EVK as USB host. Confirmed
cdc._timeoutis now 1000 after default construction andread(),write(),readinto()all work without error. Also verified explicittimeout=parameter still takes effect.