The mystery 5D is actually an "escaped" 7D (hmm or 7E -- I don't remember
which off-hand). The trailing 7E's are the "framing" bytes at the end and
beginning of each message (thus leading to the need for escaping them
elsewhere) and the last 42 is radio message type, so your framing is
off a bit. I think the remaining ??? values are the CRC and other
internal message structure. See this page for excruciating detail:
http://www.octavetech.com/pubs/TB5-01%20Deciphering%20TinyOS%20Serial%20Packets.pdf
MS
Edgar Charry wrote:
Hello everyone,
I am experimenting problems with the packet structure. I'm using the
TinyOS1.x operating system.
The TOS_Msg struc is intact, but i've changed the xsensor header a bit.
However i cannot recognized some bytes that my programm is listening
(and shouldn't be received). They are marked with a "???" below. Can
anyone PLEASE give me any sort of explanation? As strenght and ack bytes
are not sent, don't really know what they are (or where the CRC is).
My packet struc should be 5 bytes of TinyOS Header :
a. Dest Add - 2, AM Group - 1, AM Type - 1, Length - 1
another 6 bytes of xsensor header (which i changed to count the packets
supposed to be transmitted and the transmitted in fact):
b. packet_id - 2, tx_id - 2, node_id = 1, rsvd -1
and the payload that should contain 8 bytes:
c. thermistor - 2, adc2 - 2, adc3 - 2, adc4 - 2.
and:
d. 2 bytes of crc.
Leading to a total of: 21 bytes.
However listening to the UART Port using Labview i read 27 bytes everytime.
Below:
FFFF 007D 5D0E A200 A200 0700 DB01 A701 5B02 1702 CD00 C5B3 7E7E 42:
FFFF: Dest Add |
00: AMGroup |
7D: AMType|
5D = ????
0E: length (which is 14bytes and is correct)|
A200: packet id|
A200: tx id|
07: node id|
00: reserved|
DB01:Thermistor|
A701:ADC2|
5B02:ADC3|
1702:ADC4|
CD00:???
C5B3:???
7E7E:???
42:???
Thanks many times for any kind of guidance!
Edgar Charry
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--
Platform: WinXP/Cygwin
TinyOS version: 1.x, Boomerang
Programmer: MIB510
Device(s): Mica2, MicaZ, Tmote
Sensor board: homebrew
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