usb_cdc
– USB CDC Serial streams¶
The usb_cdc
module allows access to USB CDC (serial) communications.
On Windows, each Serial
is visible as a separate COM port. The ports will often
be assigned consecutively, console
first, but this is not always true.
On Linux, the ports are typically /dev/ttyACM0
and /dev/ttyACM1
.
The console
port will usually be first.
On MacOS, the ports are typically /dev/cu.usbmodem<something>
. The something
varies based on the USB bus and port used. The console
port will usually be first.
Available on these boards
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- usb_cdc.console :Optional[Serial]¶
- The
console
Serial
object is used for the REPL, and forsys.stdin
andsys.stdout
. console
isNone
if disabled.
However, note that
sys.stdin
andsys.stdout
are text-based streams, and theconsole
object is a binary stream. You do not normally need to write toconsole
unless you want to write binary data.- The
- usb_cdc.data :Optional[Serial]¶
A
Serial
object that can be used to send and receive binary data to and from the host. Note thatdata
is disabled by default.data
isNone
if disabled.
- usb_cdc.disable() None ¶
Do not present any USB CDC device to the host. Can be called in
boot.py
, before USB is connected. Equivalent tousb_cdc.enable(console=False, data=False)
.
- usb_cdc.enable(*, console: bool = True, data: bool = False) None ¶
Enable or disable each CDC device. Can be called in
boot.py
, before USB is connected.- Paramètres:
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.
- class usb_cdc.Serial¶
Receives cdc commands over USB
You cannot create an instance of
usb_cdc.Serial
. The available instances are in theusb_cdc.serials
tuple.- connected :bool¶
True if this Serial is connected to a host. (read-only)
Note
The host is considered to be connected if it is asserting DTR (Data Terminal Ready). Most terminal programs and
pyserial
assert DTR when opening a serial connection. However, the C#SerialPort
API does not. You must setSerialPort.DtrEnable
.
- in_waiting :int¶
Returns the number of bytes waiting to be read on the USB serial input. (read-only)
- out_waiting :int¶
Returns the number of bytes waiting to be written on the USB serial output. (read-only)
- timeout :Optional[float]¶
The initial value of
timeout
isNone
. IfNone
, wait indefinitely to satisfy the conditions of a read operation. If 0, do not wait. If > 0, wait onlytimeout
seconds.
- write_timeout :Optional[float]¶
The initial value of
write_timeout
isNone
. IfNone
, wait indefinitely to finish writing all the bytes passed towrite()
.If 0, do not wait. If > 0, wait onlywrite_timeout
seconds.
- read(size: int = 1) bytes ¶
Read at most
size
bytes. Ifsize
exceeds the internal buffer size only the bytes in the buffer will be read. Iftimeout
is > 0 orNone
, and fewer thansize
bytes are available, keep waiting until the timeout expires orsize
bytes are available.- Renvoie:
Data read
- Type renvoyé:
- readinto(buf: _typing.WriteableBuffer) int ¶
Read bytes into the
buf
. Ifnbytes
is specified then read at most that many bytes, subject totimeout
. Otherwise, read at mostlen(buf)
bytes.- Renvoie:
number of bytes read and stored into
buf
- Type renvoyé:
- readline(size: int = -1) bytes | None ¶
Read a line ending in a newline character ( »\n »), including the newline. Return everything readable if no newline is found and
timeout
is 0. ReturnNone
in case of error.This is a binary stream: the newline character « \n » cannot be changed. If the host computer transmits « \r » it will also be included as part of the line.
- readlines() List[bytes | None] ¶
Read multiple lines as a list, using
readline()
.Avertissement
If
timeout
isNone
,readlines()
will never return, because there is no way to indicate end of stream.- Renvoie:
a list of the line read
- Type renvoyé:
- write(buf: _typing.ReadableBuffer) int ¶
Write as many bytes as possible from the buffer of bytes.
- Renvoie:
the number of bytes written
- Type renvoyé: