Home / foxBMS Reference / CAN Module

CAN Module

Source: docs.foxbms.org — CAN Files: src/app/driver/can/can.c, can.h, can_cfg.c, can_cfg.h, can_helper.c, can_cbs.h Callbacks: src/app/driver/can/cbs/ (tx_cyclic, tx_async, rx)

TX Configuration

can_txMessages[] table defines each TX message:

Field Description
CAN ID Message identifier (11-bit standard)
DLC Data length code (max 8 bytes)
Repetition time Period in ms (multiples of 10)
Repetition phase Initial delay before first TX
Byte order Endianness (big-endian for foxBMS)
Callback Function pointer that builds the CAN data
Multiplexer Optional pointer for mux-based messages

TX Flow

  1. CAN_PeriodicTransmit() called every 10ms (from 10ms task)
  2. Checks each message: has its period elapsed?
  3. If yes → calls callback → callback encodes signals → calls canTransmit()
  4. If TX fails → queued in ftsk_canTxUnsentMessagesQueue for retry

TX Helper Functions

CAN_TxSetMessageDataWithSignalData()  // Encode signal into 64-bit message variable
CAN_TxSetCanDataWithMessageData()     // Transfer to low-level driver

RX Configuration

can_rxMessages[] table defines each RX message:

Field Description
CAN ID Message identifier
DLC Expected data length
Byte order Endianness
Callback Function pointer that decodes the CAN data

RX Flow

  1. CAN hardware ISR fires → CAN_RxInterrupt() called
  2. Message placed in ftsk_canRxQueue
  3. CAN_ReadRxBuffer() called every 1ms (from 1ms task)
  4. Dequeues frames → dispatches to matching RX callback
  5. Callbacks decode signals → write to database

RX Helper Functions

CAN_RxGetMessageDataFromCanData()     // Copy CAN frame to 64-bit variable
CAN_RxGetSignalDataFromMessageData()  // Extract individual signal

Hardware Configuration

POSIX Port Differences

Feature Production POSIX
TX HW mailbox → CAN bus posix_can_send() → SocketCAN
RX HW ISR → queue read(can_socket) → ring buffer
Mailbox 64 HW mailboxes Tracked in can_mailbox_id[] array
TX arbitration HW bus arbitration None (GA-11)
TX failure/retry HW mailbox full → queue Always succeeds on SocketCAN
E2E protection AUTOSAR counter + CRC Bypassed (GA-27)
TX period Timer ISR enforced Fires when loop reaches it (GA-26)
← DatabaseFTASK →