In CC2420ReceiveP you will find the following comment and code:
// pass packet up if crc is good
if ( ( buf[ length ] >> 7 ) && rx_buf ) {
uint8_t type = ( header->fcf >> IEEE154_FCF_FRAME_TYPE ) & 7;
signal CC2420Receive.receive( type, m_p_rx_buf );
if ( type == IEEE154_TYPE_DATA ) {
post receiveDone_task();
return;
}
}
waitForNextPacket();
(buf[length] >> 7) is the 1 or 0 from the CRC test.
If the value is 0 then it just waits for the next packet overwriting the
original once it arrives. If it is a 1 and the data type is of the format
IEEE154_TYPE_DATA then it posts a receiveDone_task which signals upper
layers:
m_p_rx_buf = signal Receive.receive( m_p_rx_buf, m_p_rx_buf->data,
length );
The code "signal CC2420Receive.receive( type, m_p_rx_buf );" is for
acknowledgements and the event for this is defined in CC2420TransmitP.
Regards,
Damien.
-----Original Message-----
From: [EMAIL PROTECTED]
[mailto:[EMAIL PROTECTED] On Behalf Of Paolo
Sent: 07 May 2008 11:37
To: tinyos-help@millennium.berkeley.edu
Subject: [Tinyos-help] CC2420 behaviour regarding CRC error
when the cc2420 radio receives a packet, it checks whether the CRC bytes
in the packet are correct or not (via HW). and then it replaces the two
CRC bytes at the
end of the packet with RSSI information and some correlation values, and
only
one bit to tell whether the recieved packet had valid CRC or not.
At this point my question is: if the bit of CRC is 0 (CRC-Error) which
is the behaviour of the radio stack ?
is launched an event ? which module launch/catch the event ? the message
is deleted from RX queue immediatly ?
thanks
Paolo.
_______________________________________________
Tinyos-help mailing list
Tinyos-help@millennium.berkeley.edu
https://www.millennium.berkeley.edu/cgi-bin/mailman/listinfo/tinyos-help
_______________________________________________
Tinyos-help mailing list
Tinyos-help@millennium.berkeley.edu
https://www.millennium.berkeley.edu/cgi-bin/mailman/listinfo/tinyos-help
