Controller area network (CAN) routines

UM0459

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2.2.10

CAN_SetTxMsgObj function

Note:

When defining which message object number to use for TX or RX, you must take into

account the priority levels when processing the objects. The lowest number (0) has the

highest priority and the highest number (31) has the lowest priority, whatever the type of the

object. Also, for optimum performance, it is recommended not to have “holes” in the object

list.

Example:

This example illustrates how to define transmit message object 0 of CAN1 with standard

identifiers and, how to disable the answer to remote frames with matching ID.

{

CAN_SetTxMsgObj(CAN1, 0, CAN_STD_ID, DISABLE);

}

Table 14.

CAN_SetTxMsgObj function description

Function name

CAN_SetTxMsgObj

Prototype

ErrorStatus CAN_SetTxMsgObj(CAN_TypeDef* CAN, u16 msgobj,

u16 idType, FunctionalSate RemotEn)

Behavior description

Configures the message object to transmit a message object with

idType passed as a parameter.

This function performs the following operations:

– searches for a free message interface from IF0 and IF1.

– Sets the WR/RD, Mask, Arb, Control, DataA and DataB bits in the

Command Mask register.

– Sets the masks to 7FF for standard ID and 0x1FFFFFFF for extended

ID.

– Sets the Mdir and MXtd

– If remote functionality is enabled, then the US_MASK is not set in the

message control register in order not to handle the remote frames

received

– Enables the message object interrupt.

– Clears the data registers

– Writes 1+msgobj into the command request register to start the

transfer to the message RAM.

Input parameter 1

CAN: pointer to a CAN1 or CAN2 CAN_TypeDef structure.

Input parameter 2

msgobj: message object number, from 0 to 31.

Input parameter 3

idType: the identifier type of the frames that will be transmitted using this

message object. The value is one of the following:

CAN_STD_ID (standard ID, 11-bit)

CAN_EXT_ID (extended ID, 29-bit)

Input parameter 4

RemoteEN: if enabled, the message object answers remote frames with

matching ID. The value is one of the following:

ENABLE: To enable the remote functionality

DISBALE: To disable the remote functionality

Output parameter

None

Return value

An ErrorStatus enumeration value:

– SUCCESS: Interface to handle the message

– ERROR: No interface to handle the message

Required preconditions

None

Called functions

CAN_GetFreeIF()