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LCP2292: CAN Receive Buffer Status
von emp (Guest)

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Hi,
I am working with a LPC2292/01 Rev. C and use the CAN interface 1 of 
this chip.

The RBS and the DOS bit in the CAN1GSR are never set.

I checked the address of the Register definition of CAN1GSR twice.

Transmitting works. Receiving works, when I ignore the RBS-Bit.

I looked at the code from the AN10438 and RBS and DOS were never 
checked. Are these Bits broken? There is nothing in the errata. How can 
you determine when there is a new message without the RBS-bit.

Has anyone an idea?

Here is my Code (initialisation and receive-function)

1
void can_init()

2
{

3
  //Reset bus

4
  C1MOD = (1 << 0);

5
6
  //Bus-Timing 25kBit (60MHz PCLK)

7
  //Prescaler: 300, SJW: 1, TESG1: 5, TESG2: 2

8
  C1BTR = 299 | (4 << 16) | (1 << 20);

9
10
  //IO

11
  PINSEL1 |= (0x01 << 18);

12
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  //activate

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  C1MOD &= ~(1 << 0);

15
}

16
17
int8_t can_read_msg(CAN_MSG * msg)

18
{

19
  //Receive

20
  if(C1GSR & 0x01)

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  {

22
    msg->len = (C1RFS >> 16) & 0x0F;  //read length

23
    msg->id = C1RID & 0x3FF;    //read ID

24
25
    if(C1RFS & (1 << 30))      //RTR?

26
    {

27
      msg->status = CAN_STATUS_RTR;  //RTR Flag

28
    }

29
    else

30
    {

31
      //no RTR, read databytes, ignore length

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      msg->data[0] = C1RDA & 0xFF;

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      msg->data[1] = (C1RDA >> 8) & 0xFF;

34
      msg->data[2] = (C1RDA >> 16) & 0xFF;

35
      msg->data[3] = (C1RDA >> 24) & 0xFF;

36
      msg->data[4] = C1RDB & 0xFF;

37
      msg->data[5] = (C1RDB >> 8) & 0xFF;

38
      msg->data[6] = (C1RDB >> 16) & 0xFF;

39
      msg->data[7] = (C1RDB >> 24) & 0xFF;

40
    }

41
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    //next time, next message

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    C1CMR = (1 << 2);

44
45
    return 0;

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  }

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  else

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  {

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    return -1;

50
  }

51
}


  


  




  

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    Re: LCP2292: CAN Receive Buffer Status
  


  

    

      von
      
        emp (Guest)
      
      


      
    


    

      
    

    

    

  
  


  

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I found it myself.

If you don't use CAN-filters, you'll have to by-pass the CAN-filters.

Setting the AccBP bit in the AFMR register does the trick.

1
AFMR |= ( 1 << 1);


  


  




  

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