CAN protocol

The CAN protocol support allows a Digilent Waveforms device to be used as a simple CAN bus device.

Todo

This section is currently incomplete.

A bit of background on CAN would be helpful.

This section does not yet properly explain the polarity setting.

It also does not yet explain the vID, extended, and remote parameters / return values used in the rx() and tx() methods.

Using the CAN protocol functionality

To use the CAN protocol functionality you first need to initialize a DwfLibrary instance. Next, you open a specific device. The device’s CAN protocol functionality can now be accessed via its protocol.can attribute, which is an instance of the ProtocolCAN class:

from pydwf import DwfLibrary
from pydwf.utilities import openDwfDevice

dwf = DwfLibrary()

with openDwfDevice(dwf) as device:
    can = device.protocol.can
    can.reset()

ProtocolCAN reference

class ProtocolCAN

The ProtocolCAN class provides access to the CAN bus protocol functionality of a DwfDevice.

Attention

Users of pydwf should not create instances of this class directly.

It is instantiated during initialization of a DwfDevice and subsequently accessible via its protocol.can attribute.

reset() → None

Reset the CAN bus protocol functionality.

Raises:: DwfLibraryError – An error occurred while executing the reset operation.

rateSet(data_rate: float) → None

Set the CAN bus data rate, in Hz.

Parameters:: data_rate (float) – The data-rate used by the receiver and transmitter.
Raises:: DwfLibraryError – An error occurred while executing the operation.

polaritySet(polarity: bool) → None

Set the CAN bus polarity.

Parameters:: polarity (bool) – If True, set polarity to high.
Raises:: DwfLibraryError – An error occurred while executing the operation.

txSet(channel_index: int) → None

Set the digital channel (pin) where the outgoing (TX) signal will be transmitted.

Parameters:: channel_index (int) – The digital channel (pin) on which to transmit data.
Raises:: DwfLibraryError – An error occurred while executing the operation.

rxSet(channel_index: int) → None

Set the digital channel (pin) where the incoming (RX) signal is received.

Parameters:: channel_index (int) – The digital channel (pin) on which to receive data.
Raises:: DwfLibraryError – An error occurred while executing the operation.

tx(v_id: int, extended: bool, remote: bool, data: bytes) → None

Transmit outgoing CAN bus data.

Parameters:

v_id (int) – (to be documented).
extended (bool) – (to be documented).
remote (bool) – (to be documented).
data (bytes) – The data to be transmitted. Should be at most 8 bytes.

Raises:

PyDwfError – A request to transmit more than 8 bytes was made.
DwfLibraryError – An error occurred while executing the operation.

rx(size: int = 8) → Tuple[int, bool, bool, bytes, int]

Receive incoming CAN bus data.

Returns:: A tuple (vID, extended, remote, data, status)
Return type:: Tuple[int, bool, bool, bytes, int]
Raises:: DwfLibraryError – An error occurred while executing the operation.

property device

Return the DwfDevice instance of which we are an attribute.

This is useful if we have a variable that contains a reference to a DwfDevice attribute, but we need the DwfDevice itself.

Returns:: The DwfDevice instance that this attribute belongs to.
Return type:: DwfDevice