Overview

This section describes the programming interface of the FlexCAN Peripheral driver.

FlexCAN Overview

The FlexCAN (flexible controller area network) module is a communication controller implementing the CAN protocol according to the CAN 2.0B protocol specification. The FlexCAN module supports both standard and extended message frames. The message buffers are stored in an embedded RAM dedicated to the FlexCAN module. The CAN Protocol Engine (PE) sub-module manages the serial communication on the CAN bus by requesting RAM access for receiving and transmitting message frames, validating received messages, and performing error handling.

FlexCAN Initialization

To initialize the FlexCAN driver, call the FLEXCAN_DRV_Init() function and pass the instance number of the FlexCAN you want to use. For example, to use FlexCAN0, pass a value of 0 to the flexcan_init function. In addition, you should also pass a user configuration structure flexcan_user_config_t, as shown here:

// FlexCAN configuration structure for user
typedef struct FLEXCANUserConfig {
    uint32_t max_num_mb;                            
    flexcan_rx_fifo_id_filter_num_t num_id_filters; 
    bool is_rx_fifo_needed;                         
} flexcan_user_config_t;

Typically, the user configures the flexcan_user_config_t instantiation as 16 message buffers, 8 RX FIFO ID filters and set to true when RX FIFO is needed. This is a code example to set up a FlexCAN configuration instantiation:

flexcan_config_t flexcan1_data;
flexcan1_data.max_num_mb = 16;
flexcan1_data.num_id_filters = kFlexCanRxFifoIDFilters_8;
flexcan1_data.is_rx_fifo_needed = true;

FlexCAN Module timing

FlexCAN bit rate is derived from the serial clock, which is generated by dividing the PE clock by the programmed PRESDIV value. Each serial clock period is also called a time quantum. The FlexCAN bit-rate is defined as the Sclock divided by the number of time quanta, where time quanta are further broken down segments within the bit time (time to transmit and sample a bit). This list shows the CAN bit-rates that are supported in the FlexCAN driver. 1 Mbytes/s 750 Kbytes/s 500 Kbytes/s 250 Kbytes/s 125 Kbytes/s

The FlexCAN module supports several different ways to set up the bit timing parameters that are required by the CAN protocol. The Control Register has various fields used to control bit timing parameters: PRESDIV, PROPSEG, PSEG1, PSEG2, and RJW.

To calculate the CAN bit timing parameters, use the method outlined in the Application Note AN1798, section 4.1. A maximum time for PROP_SEG is used, the remaining TQ is split equally between PSEG1 and PSEG2, provided PSEG2 >=2. RJW is set to the minimum of 4 or to the PSEG1.

FlexCAN Transfers

To transmit a FlexCAN frame, the CPU must prepare a message buffer for transmission by calling the FLEXCAN_DRV_Send() function. To receive the FlexCAN frames into a message buffer, the CPU must also prepare it for reception by first setting up the receive mask by calling FLEXCAN_DRV_SetMaskType(), FLEXCAN_DRV_SetRxFifoGlobalMask(), FLEXCAN_DRV_SetRxMbGlobalMask() and FLEXCAN_DRV_SetRxIndividualMask() functions. Then configure the RX buffers by calling either FLEXCAN_DRV_ConfigRxMb() or FLEXCAN_DRV_ConfigRxFifo() functions depending on the mode of reception. Finally, call FLEXCAN_DRV_RxMessageBuffer() or FLEXCAN_DRV_RxFifo functions depending on the mode of reception. The FlexCAN uses only the interrupt-driven process to transfer data.

Data Structures
struct	flexcan_state_t
	Internal driver state information. More...

struct	flexcan_data_info_t
	FlexCAN data info from user. More...

struct	flexcan_user_config_t
	FlexCAN configuration. More...

Functions
void	FLEXCAN_DRV_IRQHandler (uint8_t instance)
	Interrupt handler for a FlexCAN instance. More...

flexcan_status_t	FLEXCAN_DRV_GetTransmitStatus (uint32_t instance)
	Returns whether the previous FLEXCAN transmit has finished. More...

flexcan_status_t	FLEXCAN_DRV_GetReceiveStatus (uint32_t instance)
	Returns whether the previous FLEXCAN receive is complete. More...

Variables
CAN_Type *const	g_flexcanBase []
	Table of base addresses for FlexCAN instances. More...

const IRQn_Type	g_flexcanRxWarningIrqId []
	Table to save RX Warning IRQ numbers for FlexCAN instances. More...

const IRQn_Type	g_flexcanTxWarningIrqId []
	Table to save TX Warning IRQ numbers for FlexCAN instances. More...

const IRQn_Type	g_flexcanWakeUpIrqId []
	Table to save wakeup IRQ numbers for FlexCAN instances. More...

const IRQn_Type	g_flexcanErrorIrqId []
	Table to save error IRQ numbers for FlexCAN instances. More...

const IRQn_Type	g_flexcanBusOffIrqId []
	Table to save Bus off IRQ numbers for FlexCAN instances. More...

const IRQn_Type	g_flexcanOredMessageBufferIrqId []
	Table to save message buffer IRQ numbers for FlexCAN instances. More...

Bit rate
flexcan_status_t	FLEXCAN_DRV_SetBitrate (uint8_t instance, flexcan_time_segment_t *bitrate)
	Sets the FlexCAN bit rate. More...

flexcan_status_t	FLEXCAN_DRV_GetBitrate (uint8_t instance, flexcan_time_segment_t *bitrate)
	Gets the FlexCAN bit rate. More...

Global mask
void	FLEXCAN_DRV_SetRxMaskType (uint8_t instance, flexcan_rx_mask_type_t type)
	Sets the RX masking type. More...

flexcan_status_t	FLEXCAN_DRV_SetRxFifoGlobalMask (uint8_t instance, flexcan_msgbuff_id_type_t id_type, uint32_t mask)
	Sets the FlexCAN RX FIFO global standard or extended mask. More...

flexcan_status_t	FLEXCAN_DRV_SetRxMbGlobalMask (uint8_t instance, flexcan_msgbuff_id_type_t id_type, uint32_t mask)
	Sets the FlexCAN RX MB global standard or extended mask. More...

flexcan_status_t	FLEXCAN_DRV_SetRxIndividualMask (uint8_t instance, flexcan_msgbuff_id_type_t id_type, uint32_t mb_idx, uint32_t mask)
	Sets the FlexCAN RX individual standard or extended mask. More...

Initialization and Shutdown
flexcan_status_t	FLEXCAN_DRV_Init (uint32_t instance, flexcan_state_t state, const flexcan_user_config_t data)
	Initializes the FlexCAN peripheral. More...

uint32_t	FLEXCAN_DRV_Deinit (uint8_t instance)
	Shuts down a FlexCAN instance. More...

Send configuration
flexcan_status_t	FLEXCAN_DRV_ConfigTxMb (uint8_t instance, uint32_t mb_idx, flexcan_data_info_t *tx_info, uint32_t msg_id)
	FlexCAN transmit message buffer field configuration. More...

flexcan_status_t	FLEXCAN_DRV_SendBlocking (uint8_t instance, uint32_t mb_idx, flexcan_data_info_t tx_info, uint32_t msg_id, uint8_t mb_data, uint32_t timeout_ms)
	Sends FlexCAN messages. More...

flexcan_status_t	FLEXCAN_DRV_Send (uint8_t instance, uint32_t mb_idx, flexcan_data_info_t tx_info, uint32_t msg_id, uint8_t mb_data)
	Sends FlexCAN messages. More...

Receive configuration
flexcan_status_t	FLEXCAN_DRV_ConfigRxMb (uint8_t instance, uint32_t mb_idx, flexcan_data_info_t *rx_info, uint32_t msg_id)
	FlexCAN receive message buffer field configuration. More...

flexcan_status_t	FLEXCAN_DRV_ConfigRxFifo (uint8_t instance, flexcan_rx_fifo_id_element_format_t id_format, flexcan_id_table_t *id_filter_table)
	FlexCAN RX FIFO field configuration. More...

flexcan_status_t	FLEXCAN_DRV_RxMessageBufferBlocking (uint8_t instance, uint32_t mb_idx, flexcan_msgbuff_t *data, uint32_t timeout_ms)
	FlexCAN is waiting to receive data from the message buffer. More...

flexcan_status_t	FLEXCAN_DRV_RxMessageBuffer (uint8_t instance, uint32_t mb_idx, flexcan_msgbuff_t *data)
	FlexCAN is waiting to receive data from the message buffer. More...

flexcan_status_t	FLEXCAN_DRV_RxFifoBlocking (uint8_t instance, flexcan_msgbuff_t *data, uint32_t timeout_ms)
	FlexCAN is waiting to receive data from the message FIFO. More...

flexcan_status_t	FLEXCAN_DRV_RxFifo (uint8_t instance, flexcan_msgbuff_t *data)
	FlexCAN is waiting to receive data from the message FIFO. More...

Data Structure Documentation

struct flexcan_state_t

Note: The contents of this structure are internal to the driver and should not be modified by users. Also, contents of the structure are subject to change in future releases.

Data Fields
flexcan_msgbuff_t *	fifo_message
	The FlexCAN receive FIFO data.

flexcan_msgbuff_t *	mb_message
	The FlexCAN receive MB data.

volatile uint32_t	rx_mb_idx
	Index of the message buffer for receiving.

volatile uint32_t	tx_mb_idx
	Index of the message buffer for transmitting.

semaphore_t	txIrqSync
	Used to wait for ISR to complete its TX business. More...

semaphore_t	rxIrqSync
	Used to wait for ISR to complete its RX business. More...

volatile bool	isTxBusy
	True if there is an active transmit. More...

volatile bool	isRxBusy
	True if there is an active receive. More...

volatile bool	isTxBlocking
	True if transmit is blocking transaction. More...

volatile bool	isRxBlocking
	True if receive is blocking transaction. More...

Field Documentation

semaphore_t flexcan_state_t::txIrqSync

semaphore_t flexcan_state_t::rxIrqSync

volatile bool flexcan_state_t::isTxBusy

volatile bool flexcan_state_t::isRxBusy

volatile bool flexcan_state_t::isTxBlocking

volatile bool flexcan_state_t::isRxBlocking

struct flexcan_data_info_t

Data Fields
flexcan_msgbuff_id_type_t	msg_id_type
	Type of message ID (standard or extended)

uint32_t	data_length
	Length of Data in Bytes.

struct flexcan_user_config_t

Data Fields
uint32_t	max_num_mb
	The maximum number of Message Buffers.

flexcan_rx_fifo_id_filter_num_t	num_id_filters
	The number of RX FIFO ID filters needed.

bool	is_rx_fifo_needed
	1 if needed; 0 if not. More...

flexcan_operation_modes_t	flexcanMode
	User configurable FlexCAN operation modes.

Field Documentation

bool flexcan_user_config_t::is_rx_fifo_needed

This controls whether the Rx FIFO feature is enabled or not.

Function Documentation

flexcan_status_t FLEXCAN_DRV_SetBitrate	(	uint8_t	instance,
		flexcan_time_segment_t *	bitrate
	)

Parameters

instance	A FlexCAN instance number
bitrate	A pointer to the FlexCAN bit rate settings.

Returns: 0 if successful; non-zero failed

flexcan_status_t FLEXCAN_DRV_GetBitrate	(	uint8_t	instance,
		flexcan_time_segment_t *	bitrate
	)

Parameters

instance	A FlexCAN instance number
bitrate	A pointer to a variable for returning the FlexCAN bit rate settings

Returns: 0 if successful; non-zero failed

void FLEXCAN_DRV_SetRxMaskType	(	uint8_t	instance,
		flexcan_rx_mask_type_t	type
	)

Parameters

instance	A FlexCAN instance number
type	The FlexCAN RX mask type

flexcan_status_t FLEXCAN_DRV_SetRxFifoGlobalMask	(	uint8_t	instance,
		flexcan_msgbuff_id_type_t	id_type,
		uint32_t	mask
	)

Parameters

instance	A FlexCAN instance number
id_type	Standard ID or extended ID
mask	Mask value

Returns: 0 if successful; non-zero failed

flexcan_status_t FLEXCAN_DRV_SetRxMbGlobalMask	(	uint8_t	instance,
		flexcan_msgbuff_id_type_t	id_type,
		uint32_t	mask
	)

Parameters

instance	A FlexCAN instance number
id_type	Standard ID or extended ID
mask	Mask value

Returns: 0 if successful; non-zero failed

flexcan_status_t FLEXCAN_DRV_SetRxIndividualMask	(	uint8_t	instance,
		flexcan_msgbuff_id_type_t	id_type,
		uint32_t	mb_idx,
		uint32_t	mask
	)

Parameters

instance	A FlexCAN instance number
id_type	A standard ID or an extended ID
mb_idx	Index of the message buffer
mask	Mask value

Returns: 0 if successful; non-zero failed.

flexcan_status_t FLEXCAN_DRV_Init	(	uint32_t	instance,
		flexcan_state_t *	state,
		const flexcan_user_config_t *	data
	)

This function initializes

Parameters

instance	A FlexCAN instance number
state	Pointer to the FlexCAN driver state structure.
data	The FlexCAN platform data

Returns: 0 if successful; non-zero failed

uint32_t FLEXCAN_DRV_Deinit ( uint8_t instance )

Parameters

instance A FlexCAN instance number

Returns: 0 if successful; non-zero failed

flexcan_status_t FLEXCAN_DRV_ConfigTxMb	(	uint8_t	instance,
		uint32_t	mb_idx,
		flexcan_data_info_t *	tx_info,
		uint32_t	msg_id
	)

Parameters

instance	A FlexCAN instance number
mb_idx	Index of the message buffer
tx_info	Data info
msg_id	ID of the message to transmit

Returns: 0 if successful; non-zero failed

flexcan_status_t FLEXCAN_DRV_SendBlocking	(	uint8_t	instance,
		uint32_t	mb_idx,
		flexcan_data_info_t *	tx_info,
		uint32_t	msg_id,
		uint8_t *	mb_data,
		uint32_t	timeout_ms
	)

Parameters

instance	A FlexCAN instance number
mb_idx	Index of the message buffer
tx_info	Data info
msg_id	ID of the message to transmit
mb_data	Bytes of the FlexCAN message
timeout_ms	A timeout for the transfer in milliseconds.

Returns: 0 if successful; non-zero failed

flexcan_status_t FLEXCAN_DRV_Send	(	uint8_t	instance,
		uint32_t	mb_idx,
		flexcan_data_info_t *	tx_info,
		uint32_t	msg_id,
		uint8_t *	mb_data
	)

Parameters

instance	A FlexCAN instance number
mb_idx	Index of the message buffer
tx_info	Data info
msg_id	ID of the message to transmit
mb_data	Bytes of the FlexCAN message.

Returns: 0 if successful; non-zero failed

flexcan_status_t FLEXCAN_DRV_ConfigRxMb	(	uint8_t	instance,
		uint32_t	mb_idx,
		flexcan_data_info_t *	rx_info,
		uint32_t	msg_id
	)

Parameters

instance	A FlexCAN instance number
mb_idx	Index of the message buffer
rx_info	Data info
msg_id	ID of the message to transmit

Returns: 0 if successful; non-zero failed

flexcan_status_t FLEXCAN_DRV_ConfigRxFifo	(	uint8_t	instance,
		flexcan_rx_fifo_id_element_format_t	id_format,
		flexcan_id_table_t *	id_filter_table
	)

Parameters

instance	A FlexCAN instance number
id_format	The format of the RX FIFO ID Filter Table Elements
id_filter_table	The ID filter table elements which contain RTR bit, IDE bit, and RX message ID

Returns: 0 if successful; non-zero failed.

flexcan_status_t FLEXCAN_DRV_RxMessageBufferBlocking	(	uint8_t	instance,
		uint32_t	mb_idx,
		flexcan_msgbuff_t *	data,
		uint32_t	timeout_ms
	)

Parameters

instance	A FlexCAN instance number
mb_idx	Index of the message buffer
data	The FlexCAN receive message buffer data.
timeout_ms	A timeout for the transfer in milliseconds.

Returns: 0 if successful; non-zero failed

flexcan_status_t FLEXCAN_DRV_RxMessageBuffer	(	uint8_t	instance,
		uint32_t	mb_idx,
		flexcan_msgbuff_t *	data
	)

Parameters

instance	A FlexCAN instance number
mb_idx	Index of the message buffer
data	The FlexCAN receive message buffer data.

Returns: 0 if successful; non-zero failed

flexcan_status_t FLEXCAN_DRV_RxFifoBlocking	(	uint8_t	instance,
		flexcan_msgbuff_t *	data,
		uint32_t	timeout_ms
	)

Parameters

instance	A FlexCAN instance number
data	The FlexCAN receive message buffer data.
timeout_ms	A timeout for the transfer in milliseconds.

Returns: 0 if successful; non-zero failed

flexcan_status_t FLEXCAN_DRV_RxFifo	(	uint8_t	instance,
		flexcan_msgbuff_t *	data
	)

Parameters

instance	A FlexCAN instance number
data	The FlexCAN receive message buffer data.

Returns: 0 if successful; non-zero failed

void FLEXCAN_DRV_IRQHandler ( uint8_t instance )

Parameters

instance The FlexCAN instance number.

flexcan_status_t FLEXCAN_DRV_GetTransmitStatus ( uint32_t instance )

When performing an async transmit, call this function to ascertain the state of the current transmission: in progress (or busy) or complete (success).

Parameters

instance The FLEXCAN module base address.

Returns: The transmit status.

Return values

kStatus_FLEXCAN_Success	The transmit has completed successfully.
kStatus_FLEXCAN_TxBusy	The transmit is still in progress.

flexcan_status_t FLEXCAN_DRV_GetReceiveStatus ( uint32_t instance )

When performing an async receive, call this function to find out the state of the current receive progress: in progress (or busy) or complete (success).

Parameters

instance	The FLEXCAN module base address.
bytesRemaining	A pointer to a value that is filled in with the number of bytes which still need to be received in the active transfer.

Returns: The receive status.

Return values

kStatus_FLEXCAN_Success	The receive has completed successfully.
kStatus_FLEXCAN_RxBusy	The receive is still in progress.

Variable Documentation

CAN_Type* const g_flexcanBase[]

const IRQn_Type g_flexcanRxWarningIrqId[]

const IRQn_Type g_flexcanTxWarningIrqId[]

const IRQn_Type g_flexcanWakeUpIrqId[]

const IRQn_Type g_flexcanErrorIrqId[]

const IRQn_Type g_flexcanBusOffIrqId[]

const IRQn_Type g_flexcanOredMessageBufferIrqId[]

Overview

FlexCAN Overview

FlexCAN Initialization

FlexCAN Module timing

FlexCAN Transfers

Data Structures

Functions

Variables

Bit rate

Global mask

Initialization and Shutdown

Send configuration

Receive configuration

Data Structure Documentation

Data Fields

Field Documentation

Data Fields

Data Fields

Field Documentation

Function Documentation

Variable Documentation