Thanks for your time again, you pointed me to locations that would
take lots of time for me to find by myelf. Yeah you are right I
really don't know a lot about networking. I will try to learn
more!
On Tue, Oct 16, 2012 at 3:25 PM, Saeid
Yazdani <[email protected]>
wrote:
Thanks for your comments Eric
These bytes, I directly write them to serial port of
PC, I mean they are inside a byte array, so I guess it
should be counted as serial line.
No . If you have them inside the byte array and you
write them to the port you use to talk to the serial port,
they may or maynot be the bytes that show up on the serial
line. Depends on what is running below the interface you
are using.
The mote (on the other end of the serial line) is running
HDLC at the lowest layer. This means you need to have a
protocol engine running that knows how to talk HDLC on the
serial line.
I am really confused with these layer stuff.
These are WSNs we are dealing with. Wireless Sensor Networks. Which means
you should understand basic networking. When you connect
two devices up, one needs to define how they communicate.
This is called a protocol. As data moves up the
different layers, the layers implement different
functionality, different protocols are used to provide
that functionality. The whole thing is called a protocol
stack.
It seems
that you dont understand what I am talking about. And
this list isn't the place to fix that. I'd recommend you
take a basic networking class and fill in the blanks.
What do you mean if it is coming from upper layer (I
mean what is upper layer?) it is bad? I think since this
is directly being written into serial port so I guess
it is the serial line you mentioned.
See above.
It at least toggles the Led0 of telosb motes
unclear exactly what that means. It probably means that
it received a packet.
, I reviewed the code for BaseStation app and I think
if a packet being transmitted in , maybe!, correct
format the BaseStation app toggles that LED.
If you are sending those bytes exactly as written, then
you are effectively faking a properly formatted HDLC packet
so the mote will receive it and the app on the mote (top
layer) will blink the led because it is happy.
But the PC side of what you are doing is not running the
HDLC protocol and it won't get you very far as far a general
communications with the mote.
In TEP113 there are two bytes '7d5d',
I assume this is a case of delimiter usage (so when
converting to integer or ascii to it should be treaded
as a single byte '7d' I guess).
Got look at the HDLC reference I sent above. To answer
your question what is going on is the original data in the
payload is indeed 0x7d, this is getting escaped to 0x 7d
5d. If the data were 0x7e that also would be escaped to
0x7d 0x5e.
Would you mind giving some comments about my new
discoveries!! if you mind?!
It is really important when dealing with this technology
that you have a good foundation. Seriously, go take a good
networking course.
Learn about simple serial point to point protocols.
Regards,
Sean.
On 17-10-2012 0:04, Eric Decker wrote:
On Tue, Oct 16, 2012 at 3:22
AM, Sean Dekker <[email protected]>
wrote:
Hello,
If anyone remember I was asking for serial
packet format quite a while ago. I managed
to make a packet and send it to BaseStation
app, by sending this packet, the Led0 (Red
LED) of the telosb mote toggles. I assume
this means the packet has been transfred
from PC to mote in correct format. Is this
right?
Here is the packet I managed to make:
Where are you observing these bytes?
7e is an hdlc start/end delimiter, 7d is the
hdlc escape that is used to escape both 7e and 7d
which can't occur in the body of the packet.
If you are sending this bytes from an upper layer
then it is wrong. If this is what you are
observing on the serial line then that is much
better.
I'm not sure where you are getting your data
from. Take a look at the bottom of TEP 113. The format you have
listed below is wrong. Its close though.
The sequence number is 1 byte. It is followed by
what they call the dispatch byte but really is
packet format identifier. 00 says the packet
payload is in the AM format (Active Messaging).
7E 44 00 00 FF FF 00
00 02 06 00 00 64 7B 7E
byte[0] = 0x7E //start bit
byte[1] = 0x44 //Message Type
byte[2,3] = 0x0000 //Sequence number
byte[4,5] = 0xFFFF //Destination Address
(AM_BROADCAST = 65535)
byte[6,7] = 0x0000 //Source Address
byte[8] = 0x02 //Payload size, in this case
payload is 2 bytes both zero
byte[9,10] = 0x0000 //My messege (payload)
to be sent
byte[11,12] = 0x647B //Calculated CRC from
byte[1] to byte [10]
byte[13] = 0x7E //end bit
Can somone please confirm that I am making a
correct packet and if it is accodring to the
format? also is the byte[2,3] really the
Sequence Number!? What are they being used
for? How can I take care of escape sequence?
Does somone have a C/C# code for this case?!
