FlexCAN Bus off when trying to send a message M5282 CW7.1.1

francois_boucha — Fri, 14 May 2010 00:37:50 GMT

Hi all,

I got a simple setup of 2 M5282 eval board connected together with a CAN bus. The passive side is waiting for an incomming CAN message. The other side is supposed to send 5 CAN messages but when attempting to send a message the bus becomes off.

Just after the initialization sequence the registers have these value:

MCF_FlexCAN_CANMCR==0
MCF_FlexCAN_ESTAT==80 // bus is idle
MCF_FlexCAN_IFLAG==0

 //  Init sequence
        // F sys = 64 MHz
        // CAN baud rate = 1 Mbps /* Set PASPA2,3 bits to one to assign port to CAN bus function */ MCF_PAD_PASPAR |= (MCF_PAD_PASPAR_PASPA2_CANTX |        MCF_PAD_PASPAR_PASPA3_CANRX); MCF_FlexCAN_CANCTRL2 = 0; MCF_FlexCAN_PRESDIV = (uint8) MCF_FlexCAN_PRESDIV_PRES_DIV(
                                ((SYSTEM_CLOCK_MHZ / 8) - 1) );  // Init message buffers //------------------------------------------------ /* Initialize 16 Message Buffers */ /* Descr.  used for     ID    Mask*/ //------------------------------------------------ // BUF0  Rx      slot_id   111111xxxxx     // BUF1   Rx      slot_id   111111xxxxx     // BUF2  Rx      slot_id   111111xxxxx     // BUF3   Rx      slot_id   111111xxxxx   // BUF4  Rx      slot_id   111111xxxxx    // BUF5   Rx      slot_id   111111xxxxx  // BUF6  Rx      slot_id   111111xxxxx    // BUF7   Rx      slot_id   111111xxxxx  // BUF8  Rx      slot_id   111111xxxxx  // BUF9  Rx      slot_id   111111xxxxx   // BUF10 Rx      slot_id   111111xxxxx   //------------------------------------------------ // BUF11  Rx      0    111111xxxxx   // BUF12  Rx      0    111111xxxxx   //------------------------------------------------ // BUF13 Tx    xxxxxxx     - // BUF14 Tx       xxxxxxx     - //------------------------------------------------ // BUF15  not used     -      - //------------------------------------------------   // check ID: 6 bits if(CAN_ID > 63) {  return FALSE;  }  // Rx mailboxes    for(i = 0;  BSP_RX_mailbox[i] != -1; ++i)    {     // Make buffer inactive      MCF_FlexCAN_MBUF_CTRL( BSP_RX_mailbox[i]) = MB_NOT_ACTIVE;           // for RX_BROADCAST_MAILBOX1 AND RX_BROADCAST_MAILBOX2, CAN_ID == 0     MCF_FlexCAN_MBUF_IDH( BSP_RX_mailbox[i])  = 0; // default          // All Rx mailboxes except RX_BROADCAST_MAILBOX1 AND RX_BROADCAST_MAILBOX2     if(BSP_RX_mailbox[i] != RX_BROADCAST_MAILBOX1 && BSP_RX_mailbox[i]!= RX_BROADCAST_MAILBOX2)      MCF_FlexCAN_MBUF_IDH( BSP_RX_mailbox[i])  = (uint16)(CAN_ID << 10);   // Initialise control/status word     MCF_FlexCAN_MBUF_CTRL( BSP_RX_mailbox[i]) = MB_RX_EMPTY;     }    // Tx mailboxes    for(i = 0;  BSP_TX_mailbox[i] != -1; ++i)    {     MCF_FlexCAN_MBUF_CTRL( BSP_TX_mailbox[i]) = MB_TX_NOT_READY; /* Initialise control/status word */         }       /* Message buffer(s) 15 not in use */    MCF_FlexCAN_MBUF_CTRL(15) = MB_NOT_ACTIVE; /* Make buffer inactive */            MCF_FlexCAN_RXGMASK = (uint32)(0x7e0 << 21) | (0x3ffff << 1); // Init Interrupts init_CAN_interrupts(); MCF_FlexCAN_CANMCR = 0;

Init sequence

but when attempting to transmit, the IFLAG is never set, and no message is transmitted.

       /* Hold Message Buffer ie. not ready for transmit */
    MCF_FlexCAN_MBUF_CTRL(mailbox) = MB_TX_NOT_READY;

    // Fill mailbox
    MCF_FlexCAN_MBUF_WORD(mailbox, 0) = (uint32)(word0 | (word1 << 16));
    MCF_FlexCAN_MBUF_WORD(mailbox, 1) = (uint32)(word2 | (word3 << 16));
   
           
    /* Activate transmission of Message Buffer */
    MCF_FlexCAN_MBUF_CTRL(mailbox) = MB_TX_ONCE;

    // wait
    count=0;
    while(!(MCF_FlexCAN_IFLAG & MCF_FlexCAN_IFLAG_BUF(mailbox)))
    {
        count++;
       
       
        //if(count > MAXcount)    MAXcount=count;
        // stop if too long
        if(count >= 32000)
            break;
       
    }

Any hints? Bus is terminated on both sides.

Re: FlexCAN Bus off when trying to send a message M5282 CW7.1.1

JulienP — Fri, 17 Dec 2010 06:29:20 GMT

Hello sir,

Have you fixed your problem? Because I got something similar, but in my case data are transmitted continuously, instead of one time. So BUS OFF is set. Do you have any idea? (Loopback mode is working great).

Re: FlexCAN Bus off when trying to send a message M5282 CW7.1.1

dragi_pandeliev — Tue, 15 Mar 2011 18:34:18 GMT

Have you configured correctly your bit timings? Tseg1 and Tseg2?

I had the same problem and I needed to reconfigure everything with the correct settings and then it worked.

Re: FlexCAN Bus off when trying to send a message M5282 CW7.1.1

David_UCT — Thu, 24 Mar 2011 06:29:13 GMT

if your bit timing is wrong the nodes will continuously transmit until they go Bus_OFF. In that case I would recommend you have a look at freescales application note for Bit timing, AN1798 I think just keyword search for it.

If you disconnect the nodes from each other and transmit messages you should be able to see a continuous repeat of messages on a scope to verify that the individual nodes are working.

topic Re: FlexCAN Bus off when trying to send a message M5282 CW7.1.1 in ColdFire/68K Microcontrollers and Processors

FlexCAN Bus off when trying to send a message M5282 CW7.1.1

Re: FlexCAN Bus off when trying to send a message M5282 CW7.1.1

Re: FlexCAN Bus off when trying to send a message M5282 CW7.1.1

Re: FlexCAN Bus off when trying to send a message M5282 CW7.1.1