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Diffstat (limited to 'docs/library/pyb.CAN.rst')
| -rw-r--r-- | docs/library/pyb.CAN.rst | 21 |
1 files changed, 20 insertions, 1 deletions
diff --git a/docs/library/pyb.CAN.rst b/docs/library/pyb.CAN.rst index 5fe4c2ecf..09b97a187 100644 --- a/docs/library/pyb.CAN.rst +++ b/docs/library/pyb.CAN.rst @@ -187,11 +187,12 @@ Methods Return ``True`` if any message waiting on the FIFO, else ``False``. -.. method:: CAN.recv(fifo, \*, timeout=5000) +.. method:: CAN.recv(fifo, list=None, \*, timeout=5000) Receive data on the bus: - *fifo* is an integer, which is the FIFO to receive on + - *list* is an optional list object to be used as the return value - *timeout* is the timeout in milliseconds to wait for the receive. Return value: A tuple containing four values. @@ -201,6 +202,24 @@ Methods - The FMI (Filter Match Index) value. - An array containing the data. + If *list* is ``None`` then a new tuple will be allocated, as well as a new + bytes object to contain the data (as the fourth element in the tuple). + + If *list* is not ``None`` then it should be a list object with a least four + elements. The fourth element should be a memoryview object which is created + from either a bytearray or an array of type 'B' or 'b', and this array must + have enough room for at least 8 bytes. The list object will then be + populated with the first three return values above, and the memoryview object + will be resized inplace to the size of the data and filled in with that data. + The same list and memoryview objects can be reused in subsequent calls to + this method, providing a way of receiving data without using the heap. + For example:: + + buf = bytearray(8) + lst = [0, 0, 0, memoryview(buf)] + # No heap memory is allocated in the following call + can.recv(0, lst) + .. method:: CAN.send(data, id, \*, timeout=0, rtr=False) Send a message on the bus: |