AN1105 datasheet(30/100 Pages) STMICROELECTRONICS

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ST7 pCAN PERIPHERAL DRIVER

Now look at the can_custom.h file:

There are several #define statements, including:

#define INIT_FHRi 0x00

#define INIT_FLRi 0x00

where i is either 0 or 1.

These are the two registers containing hardware filters. In the FHRi register, the 8 MSBs for

the filters are given, and in the second register the 4 LSBs are given followed by 4 zeros.

We have to do the same thing for the mask. First, let’s write 0 for the filter.

Finally we have:

#define INIT_FHR0 0x80

#define INIT_FLR0 0x00

#define INIT_MHR0 0x9F

#define INIT_MLR0 0xE0

Doing the same thing with the other group of identifiers leads to:

#define INIT_FHR1 0x20

#define INIT_FLR1 0x20

#define INIT_MHR1 0xA9

#define INIT_MLR1 0x30

Software Filter Configuration

You need to use software filtering feature if the hardware cannot stop all the undesired identi-

fiers. Look at the following code in can_custom.h:

//SOFTWARE ACCEPTANCE MASKS

//#define FILTERS_ENABLED

//#define INIT_FILTERS {}

To allow software filtering, remove the “//” comment signs, and enter the identifiers between

the parentheses. Please note that the filters must be given in hexadecimal format with four

digits, always terminated by zero, and in increasing order.

That is to say in our case:

SOFTWARE ACCEPTANCE MASKS: optional choice

#define FILTERS_ENABLED

#define INIT_FILTERS {0x1270,0x3110,0x3a50,0x5000,0x6000}

Note: There can not be more than 127 identifiers in the array.

2.2.3 Implementing the Notification Functions

The cell is now configured, we no longer need to worry about hardware.

AN1105 датащи(PDF) 30 Page - STMicroelectronics