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CCS CAN Bus dev board - auto RTR problem

 
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TL



Joined: 15 Sep 2003
Posts: 75

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CCS CAN Bus dev board - auto RTR problem
PostPosted: Mon Jan 22, 2007 4:33 am     Reply with quote
In section 18 of the exercise book, I cannot get the auto RTR to work. All I got from Node B was the following (via RS232):

Data received!
0 0 0 0 0 0 0 0
00000500

and repeats...

The 'receive' buffer is all 0's, and rx_len is also 0. The can_kbhit() function returned a 1. The ID received is correct at 0x500.

Ideally, it should be the following (according to the exercise book):
Data received!
15 14 13 12 11 10 9 8
00000500

and repeats...

I have included the code for Nodes A and B (see below). I would appreciate any comments.


Node A:
Code:

#include <18F4580.h>
//#device ICD=TRUE
#fuses HS,NOPROTECT,NOLVP,NOWDT
#use delay(clock=20000000)
#use rs232(baud=9600, xmit=PIN_C6, rcv=PIN_C7)
#include <can-18F4580.c>

void main()
{
   int32 rx_id;
   int rx_len, i;
   struct rx_stat stat;
   int data[8]={15,14,13,12,11,10,9,8};
   int receive[8];

   can_init();

   can_set_functional_mode(1);

   can_enable_b_transfer(B1);

   can_disable_filter(0xFFFF);
   can_enable_filter(0x01);

   can_set_id(RX0MASK,0xFF00,TRUE);
   can_set_id(RXFILTER0,0x500,TRUE);
   can_set_id(B1ID,0x500,TRUE);

   can_associate_filter_to_mask(ACCEPTANCE_MASK_0,F0BP);
   can_associate_filter_to_buffer(AB1,F0BP);

   can_load_rtr(B1,data,8);
   can_enable_rtr(B1);

   while(TRUE);
}


Node B:
Code:

#include <16F876A.h>
//#device ICD=TRUE
#fuses HS,NOPROTECT,NOLVP,NOWDT
#use delay(clock=2500000)
#use rs232(baud=9600, xmit=PIN_C6, rcv=PIN_C7)
#include <can-mcp2510.c>

void main()
{
   int32 rx_id=0;
   int rx_len=0, i;
   struct rx_stat stat;
   int data[8]={7,6,5,4,3,2,1,0};
   int receive[8]={0,0,0,0,0,0,0,0};

   can_init();

   while(TRUE)
   {
      can_putd(0x500,data,8,3,TRUE,TRUE);
      delay_ms(1000);

      if ( can_kbhit() )
      {
          can_getd(rx_id, receive, rx_len, stat);
          printf("Data received!\n\r");
          for(i=0; i<8; i++)
             printf("%i ",receive[i]);

          printf("\n\r%Lx\n\r",rx_id);
      }
      else
      {
          printf("Data not received.\n\r");
      }
   }
}
sjbaxter



Joined: 26 Jan 2006
Posts: 141
Location: Cheshire, UK

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PostPosted: Mon Jan 22, 2007 10:49 am     Reply with quote
I haven't used the CAN dev board, but from your code I suspect the nodes are running at different CAN bit rates.

My assumption is based on NodeA has a #using delay(20000000) and NodeB is set up to be #using delay(2500000).

At no point do you then set the baud rate of the CAN controller other than a standard call to can_init() which will set the baud rate registers to the same values (and based on different clocks ... will give different bit rates !!!).

BTW: RTR is a CAN feature that is not generally used in 'real world' applications. If you haven't already got the nodes talking using simple tx and rx can messages, then I would get that working before moving onto RTR.
_________________
Regards,
Simon.
TL



Joined: 15 Sep 2003
Posts: 75

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PostPosted: Mon Jan 22, 2007 4:20 pm     Reply with quote
Thanks for replying.

According to the exercise book, all nodes on the bus have the same target bit time and the baud rate is set in can-18F4580.h and .c for Node A, and can-mcp2515.h and .c for Node B. Apart from EX7 and EX18, all the examples work satisfactorily. All other examples use 20MHz for Node A and 2.5MHz for Node B. Note: The MCP2515 in Node B has a prescaler of 8 which divides the 20MHz to 2.5MHz for the PIC16F876A. Therefore, I assume the bit timings and baud rates for both nodes are the same. However, I need to use some tables on the web to check the figures.

CCS have confirmed that in EX7, there is a configuration problem for GP7 pin of MCP25050, and therefore the decimal point of the 7-segment display does not work. However, they did not warn me (and I assume other users as well!) about this problem when I bought the dev kit. I have spent time in debugging it. They should warn users in order to save users time. I will tell them to either tell new users about it or change the wording in EX7.

I have also written to CCS regarding EX18, but I have yet to receive a reply from them for a few weeks.
rwskinner



Joined: 08 Dec 2006
Posts: 125
Location: Texas

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PostPosted: Wed Jan 24, 2007 6:49 am     Reply with quote
TL wrote:
Thanks for replying.
.


The Can Dev board and examples are set for 125K. Unless you went in and changed the header files.

I haven't tried Auto RTR yet but everything else seemed to work after making it past all the typos and incorrect header file includes that don't exist.
TL



Joined: 15 Sep 2003
Posts: 75

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PostPosted: Thu Jan 25, 2007 2:23 am     Reply with quote
Thanks for your information.
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