Flexcan Acceptance filter mechanism

steffenrose — Tue, 23 Sep 2014 08:01:19 GMT

I use the K60 Flexcan to receive CAN messages. I use the RX Fifo. RFFN is set to 3, MB0..13 are part of the RX Fifo.

I can set the Filters to receive all messages. This works.

Now I want to use the filter mecahnism. I want to use the ID Filter table Format B. Individual filter are activated.

My problem:

All messages are receiving. Filterhit is 1.

I do not find detail information in case I use the Format B ID Table.

Which ID Filter works with which Indiviual mask?

Which entrie (combination) receive my messages and set the filterhit to 1.

My test setting (later I want to receive only specific IDs):

/* compare all mask bits */

pCan->CTRL2 |= FLEXCAN_CTRL2_EACEN;

/* store RTR frames */

pCan->CTRL2 |= FLEXCAN_CTRL2_RRS;

/* Set Scan priority (RX Fifo first) */

pCan->CTRL2 &= ~FLEXCAN_CTRL2_MRP;

/* RX Fifo */

pCan->MCR |= FLEXCAN_MCR_FEN;

// RFFN is 3

pCan->CTRL2 = (pCan->CTRL2 & ~FLEXCAN_CTRL2_RFFN )

| (FLEXCAN_RFFN_VAL << FLEXCAN_CTRL2_RFFN_BIT_NO);

/* Set ID filter table format (RX Fifo mask - Format B / 01 ) */

pCan->MCR = (pCan->MCR & ~FLEXCAN_MCR_IDAM_MASK) | FLEXCAN_MCR_IDAM(1);

/* Initialize mask registers - not relevant, I think */

pCan->RXMGMASK = 0x1FFFFFFFul;

pCan->RX14MASK = 0x1FFFFFFFul;

pCan->RX15MASK = 0x1FFFFFFFul;

//Test setting

// first should only receive, if bit 0 is set

// second only, if Bit1 is set

// next Bit 2 is set

// and so on

// the higher ID (RXIDB_0) should only receive 0x7FF - ignored for this test

for(i = 0; i <= 13 ; i++)

{

pCan->RXIMR[i] = 0xFFFF0000ul | (1ul<<i);// individual masks

}

for(i = 0; i < (14-6)*4 ; i++)

{

FLEXCAN1_IDFLT_TAB(i) = 0x07FF07FFul;

}

pCan->RXFGMASK = 0xFFFFFFFFul; //mask for all other IDs

Re: Flexcan Acceptance filter mechanism

Kan_Li — Tue, 23 Sep 2014 09:00:20 GMT

Hi Steffen Rose,

The attachment is the flexcan validation code, please kindly refer to it for details.

Hope that helps,

Have a great day,
Kan

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Re: Flexcan Acceptance filter mechanism

steffenrose — Wed, 24 Sep 2014 13:11:29 GMT

Thank you. I could use it to experiment with different settings.

Special thank, that your package was for my environment!

bye

Steffen

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