AN1105 datasheet(19/100 Pages) STMICROELECTRONICS

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ST7 pCAN PERIPHERAL DRIVER

– Error ITs are only processed if the DEBUG option was chosen in can_custom.h. Then, the

application is notified of any other events through function calls. (Functions entered in

can_custom.c).

2.1.5 User Interface Description

This section describes the user interface in a “black-box” way. The parameters and the return

values of the function declared in can.h and can_custom.h are described in this section. For a

complete description of the algorithms and internal data type variables, please see Section 3

"Detailed Description".

2.1.5.1 Data-type Variables

CAN_Buffer -type variables

typedef struct CAN_Buffer{

u16msg_identifier;

CAN_Data_Size data_size;

u8 CAN_msg_data[CAN_MAX_DATA_SIZE];

CAN_Bool buffer_rw;

CAN_Bool buffer_free;

}CAN_Buffer;

Software representation of CAN data. The translation into hardware buffers is performed by

the driver.

A variable of this data-type must be passed to the driver each time it is requested by the

CAN_Request_Buffer notification function (See “Functions called unconditionally” on

page 26). Otherwise, data in the hardware buffer will be lost.

A pointer to this structure is also used as parameter of the CAN_Transmit_Request function

(See “Functions” on page 21).

–

msg_identifier: 2 bytes field containing the identifier of the CAN message. The identifier is

stored in the 12 most significant bits. The 4 least significant bits MUST be zero. The u16

type means 2 bytes unsigned variable and is defined in lib.h.

–

data_size: 1 byte field containing the length of the data in the message (in bytes). The

CAN_Data_Size type is an enum type (See below for its description).

–

CAN_msg_data: array of 8 bytes containing the data to be sent. The u8u16 type means 1

byte unsigned variable and is defined in lib.h.

–

buffer_rw: this boolean variable is to be used as a flag to prevent simultaneous writing/

reading on the structure. It is checked and modified by the driver each time an operation

is being performed on the buffer. If CTRUE, the structure will not be read or written. If

CFALSE, it can be used. Always check/modify this variable in your application for this pur-

pose.

–

buffer_free: boolean variable used to mark if the data in the buffer can be overwritten or

not. It has to be used as the security by the user’s application. If CFALSE, the driver will

refuse to perform any write operation on the data in the structure and return an error code.

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