can_tx_statemachine.h File Reference

Orchestrates CAN frame transmission for all OpenLCB message types. More...

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Data Structures
struct	interface_can_tx_statemachine_t
	Dependency-injection interface for the CAN transmit state machine. More...

Functions
void	CanTxStatemachine_initialize (const interface_can_tx_statemachine_t *interface_can_tx_statemachine)
	Registers the dependency-injection interface for this module.
bool	CanTxStatemachine_send_openlcb_message (openlcb_msg_t *openlcb_msg)
	Converts and transmits an openlcb_msg_t as one or more CAN frames.
bool	CanTxStatemachine_send_can_message (can_msg_t *can_msg)
	Transmits a pre-built raw can_msg_t directly to the hardware.

Detailed Description

Orchestrates CAN frame transmission for all OpenLCB message types.

Copyright

Copyright (c) 2024, Jim Kueneman All rights reserved. Redistribution and use in source and binary forms, with or without modification, are permitted provided that the following conditions are met:

• Redistributions of source code must retain the above copyright notice, this list of conditions and the following disclaimer.
• Redistributions in binary form must reproduce the above copyright notice, this list of conditions and the following disclaimer in the documentation and/or other materials provided with the distribution. THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT HOLDER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.

Checks hardware buffer availability, selects the correct message-type handler, and manages multi-frame sequencing until the full payload is sent.

Author

Jim Kueneman

Date

4 Mar 2026

Function Documentation

CanTxStatemachine_initialize()

void CanTxStatemachine_initialize ( const interface_can_tx_statemachine_t * interface_can_tx_statemachine )

extern

Registers the dependency-injection interface for this module.

Parameters

interface_can_tx_statemachine

Pointer to a populated interface_can_tx_statemachine_t. Must remain valid for the lifetime of the application. All 6 pointers must be non-NULL.

Warning

NOT thread-safe - call during single-threaded initialization only.

See also

CanTxMessageHandler_initialize - initialize first

Registers the dependency-injection interface for this module.

CanTxStatemachine_send_openlcb_message()

bool CanTxStatemachine_send_openlcb_message ( openlcb_msg_t * openlcb_msg )

extern

Converts and transmits an openlcb_msg_t as one or more CAN frames.

Returns false immediately if the hardware TX buffer is not empty. Determines message type (addressed / unaddressed / datagram / stream), then loops until the entire payload is transmitted as an atomic multi-frame sequence.

Parameters

openlcb_msg

OpenLCB message to transmit. Must not be NULL.

Returns

true when the full message is transmitted, false if the TX buffer was busy or a hardware error occurred.

Warning

May block briefly while transmitting multi-frame messages.

NOT thread-safe - serialize with other callers.

See also

CanTxStatemachine_send_can_message - for raw CAN frames

Converts and transmits an openlcb_msg_t as one or more CAN frames.

Algorithm:

1. Discard immediately if state.invalid is set (AMR scrub marked it).
2. If dest_alias == 0 and dest_id != 0, resolve the alias via listener_find_by_node_id (DI, nullable). Drop the message if unresolvable (return true so the caller clears the outgoing slot).
3. Return false immediately if the TX hardware buffer is busy.
4. If payload_count == 0: send a single zero-payload frame and return.
5. Otherwise, send the first frame; if it fails return false.
6. Loop calling _transmit_openlcb_message until payload_index == payload_count.
7. Return true when done.

* @param openlcb_msg Message to transmit.
* 

Returns

true if the full message was sent, false if the hardware buffer was busy or failed.

Warning

Blocks until the entire multi-frame message is sent.

CanTxStatemachine_send_can_message()

bool CanTxStatemachine_send_can_message ( can_msg_t * can_msg )

extern

Transmits a pre-built raw can_msg_t directly to the hardware.

No OpenLCB processing and no buffer-availability check — caller is responsible for ensuring the hardware is ready. Used primarily for CAN control frames (CID, RID, AMD) during alias allocation.

Parameters

can_msg

Fully-constructed CAN frame. Must not be NULL.

Returns

true on success, false on hardware failure.

See also

CanTxStatemachine_send_openlcb_message - for OpenLCB messages

Transmits a pre-built raw can_msg_t directly to the hardware.