Class CanRxHandler

Class Documentation

class CanRxHandler

A handler that stores pointers to CanRxListener and that watches CAN 1 and CAN 2 for messages. If messages are received, it checks its internal maps for a CanRxListener that matches the message identifier and CAN bus and calls the listener’s processMessage function.

Interfaces with modm receive data from CAN1 and CAN2 buses.

To use, extend CanRxListener class and create a method called processMessage. Next, call the function attachReceiveHandler, which will add the class you instantiated to a list of classes that will be handled on receive. The class you created and attached will be called by the pollCanData function every time there is a message available that has the CAN identifier matching the identifier specified in the CanRxListener constructor.

For proper closed loop motor control, it is necessary to have the pollCanData function be called at a very high frequency, so call this in a high frequency thread.

See also

CanRxListener for information about how to properly create add a listener to the handler.

See also

Can for modm CAN wrapper functions.

Note

The CAN handler can handle 64 CAN ids between [0x1E4, 0x224). In the middle of this range, CAN ids [0x201, 0x20B] are used by the DjiMotor objects to receive data from DJI branded motors. If you would like to define your own protocol, it is recommended to avoid avoid using CAN ids in this range.

Note

the DjiMotor driver reserves 0x1FF and 0x200 for commanding motors, and thus you should not attach listeners for these ids.

Public Functions

CanRxHandler(Drivers *drivers)
~CanRxHandler() = default
void attachReceiveHandler(CanRxListener *const listener)

Call this function to add a CanRxListener to the list of CanRxListener’s that are referenced when a new CAN message is received.

See also

CanRxListener

Note

do not call this function in an object that is globally (i.e. not on that stack or heap) constructed. The map that the handler uses to store listeners may or not be properly allocated if you do and undefined behavior will follow.

Note

if you attempt to add a listener with an identifier identical to something already in the CanRxHandler, an error is thrown and the handler does not add the listener.

Parameters:

listener – [in] the listener to be attached ot the handler.

Returns:

true if listener successfully added, false otherwise.

void pollCanData()

Function handles receiving messages and calling the appropriate processMessage function given the CAN bus and can identifier.

Attention

you should call this function as frequently as you receive messages if you want to receive the most up to date messages. modm’s IQR puts CAN messages in a queue, and this function clears out the queue once it is called.

void removeReceiveHandler(const CanRxListener &rxListener)

Removes the passed in CanRxListener from the CanRxHandler. If the listener isn’t in the handler, an error will be added to the ErrorController and the state of the CanRxHandler will not change.

Parameters:

rxListener – [in] The listener to remove from the handler.

Public Static Functions

static inline uint16_t lookupTableIndexForCanId(uint16_t canId)

Given a CAN identifier, returns the “normalized” id between [0, NUM_CAN_IDS), or a value >= NUM_CAN_IDS if the canId is outside the range specified.

Public Static Attributes

static uint16_t MIN_CAN_ID = 0x1E4
static uint16_t NUM_CAN_IDS = 64
static uint16_t MAX_CAN_ID = MIN_CAN_ID + NUM_CAN_IDS

Protected Functions

void attachReceiveHandler(CanRxListener *const canRxListener, CanRxListener **messageHandlerStore)
void processReceivedCanData(const modm::can::Message &rxMessage, CanRxListener *const *messageHandlerStore)
void removeReceiveHandler(const CanRxListener &canRxListener, CanRxListener **messageHandlerStore)
inline CanRxListener **getHandlerStore(CanBus bus)

Protected Attributes

Drivers *drivers
CanRxListener *messageHandlerStoreCan1[NUM_CAN_IDS]

Stores pointers to the CanRxListeners for CAN 1, referenced when a new message is received.

CanRxListener *messageHandlerStoreCan2[NUM_CAN_IDS]

Stores pointers to the CanRxListeners for CAN 2, referenced when a new message is received.