[Tinyos-help] Crc Interface in BlinkToRadio application

[Dinesh Koya]

Hi all

I tried to use the Crc interface in the BlinkToRadio application
to calculate the crc for the packets. 
For this I modified the BlinkToRadio.h as below

#ifndef BLINKTORADIO_H
#define BLINKTORADIO_H

enum
{
 TIMER_PERIOD_MILLI = 250,
 
 AM_BLINKTORADIOMSG = 6
};

typedef nx_struct BlinkToRadioMsg
{
 nx_uint16_t nodeid;
 nx_uint16_t counter;
 nx_uint16_t crc;    // this was included 
}
 BlinkToRadioMsg;

#endif

Then I modified the event void Timer0.fired(); block of 
BlinkToRadioC file as below

#include <crc.h>   // this was included
uses interface Crc;   // this was included
event void Timer0.fired()
 {
  counter++;
  //call Leds.set(counter);

  if (!busy)
  {
   BlinkToRadioMsg* btrpkt = 
   (BlinkToRadioMsg*)(call Packet.getPayload(&pkt, NULL));
   btrpkt -> nodeid = TOS_NODE_ID;
   btrpkt -> counter = counter;
   btrpkt -> crc = crc;    // this was included 
 /* command uint16_t crc16(void* buf, uint8_t len); */
   crc = call Crc.crc16(&pkt,4);   // this was included
   
   if (call AMSend.send(AM_BROADCAST_ADDR, &pkt,         sizeof(BlinkToRadioMsg)) == SUCCESS)
   {
    busy = TRUE;
   }
  }
 }

Here I did not get rightly what to pass as the 2nd parameter 
which is uint8_t len for crc16 command, so I just tried out with 4
and then I got the following result when two tmotes were running 
BlinkToRadio with node id's 1 and 2 and one tmote with 
BaseStation running with node id as 0. 
                                         (nodeid)(counter)(crc16)
00 FF FF FF FF 06 00 06 00 01    00 01    00 00 
00 FF FF FF FF 06 00 06 00 02    00 01    00 00 
00 FF FF FF FF 06 00 06 00 01    00 02    00 00 
00 FF FF FF FF 06 00 06 00 02    00 02    00 00 
00 FF FF FF FF 06 00 06 00 01    00 03    4E 63 
00 FF FF FF FF 06 00 06 00 02    00 03    4E 63 
00 FF FF FF FF 06 00 06 00 01    00 04    5E 42 
00 FF FF FF FF 06 00 06 00 02    00 04    5E 42 
00 FF FF FF FF 06 00 06 00 01    00 05    6E 21 
00 FF FF FF FF 06 00 06 00 02    00 05    6E 21 
00 FF FF FF FF 06 00 06 00 01    00 06    7E 00 
00 FF FF FF FF 06 00 06 00 02    00 06    7E 00 
00 FF FF FF FF 06 00 06 00 01    00 07    0E E7 
00 FF FF FF FF 06 00 06 00 02    00 07    0E E7 
00 FF FF FF FF 06 00 06 00 01    00 08    1E C6 
00 FF FF FF FF 06 00 06 00 02    00 08    1E C6 
00 FF FF FF FF 06 00 06 00 01    00 09    2E A5 
00 FF FF FF FF 06 00 06 00 02    00 09    2E A5 
00 FF FF FF FF 06 00 06 00 01    00 0A    3E 84 
00 FF FF FF FF 06 00 06 00 02    00 0A    3E 84 

I would like to know what exactly is to be passed to 2nd 
parameter of crc16 command and also based on the parameter
how is the crc calculated, i.e for what lenght of the packet?

I also included the wiring in BlinkToRadioAppC as

components CrcC;   //this was included
App.Crc -> CrcC;    //this was included

Could some one help me with this

Thanks for any help

Regads
Dinesh







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