Sandhya,
I've done some similar work with embedded systems interfacing with GSM
modems using RS-232(serial) connections. Basically what I had to do was
create my own interface to the GSM modem using AT commands. The micaz
platform has an RS-232 connection (the connection is usually obtained by
using a mib510/mib520 gateway) which you can use to send AT commands to
the GSM modem.
One of the first things you will need to do is create your own component
for TX/RX plain text (ASCII) over the serial port. The issue is that by
default, tinyos sends/receives ActiveMessage Packets over the serial
port, just as if it had sent/received that message over the wireless
link. You will need to change this so that you use ASCII over the serial.
Once you do this, it's simply a matter of creating the required
interface that will properly initialize the GSM modem, open TCP/UDP
sockets, and sending information over the serial port using at
commands(ie: ATD, AT+REBOOT, etc.)
Whatever GSM modem you decide to use, it should have a user manual
defining all of the AT commands it supports. Several important commands
to look for that will make your life easier: Echo -- when this is
disabled, the serial port will no longer echo AT commands sent by the
mote(enabling this when using hyperterminal/gtxterm makes your life
easier, but when programatically sending commands, you don't need this
as it makes parsing the mote's RX serial information that much harder),
verbose -- This command may/may not be available, it will simplify the
result of the AT command. Normally when you execute an AT command you
might get a response back like "OK" or "OK\r\nip address:
xxx.xxx.xxx.xx" with verbose set to the lowest setting, most results are
shortened to an integer value, which makes parsing command/responses easier.
Certain commands have timing constraints. For example if you have
opened a TCP socket, any serial output is redirected over the TCP
socket. If you need to temporarily pause the connection and run another
AT command. For my GSM modem, the key command was "+++". A good GSM
modem user guide should have this information documented, however.
Good luck with your endeavor,
-Paul
On 12/29/2009 4:21 AM, Sandhya Sourirajan wrote:
Dear Sir/ Madam,
I am Sandhya Sourirajan doing my final year, B.E- EEE in Coimbatore
Institute of Technology. I am currently doing a project involving
Wireless Sensor Networks using the Crossbow's micaz motes for
building an intrusion detection system.
I checked out the Wireless Sensor Networks REsearch group website and
learnt about the developments in this field by sending messages
through GSM modules. However no infomation on furnished on interfacing
the GSm modules with motes and the conversion of the AT command set to
nesC.
We would be using GSM modules in our project and the gateway is
connected to the GSM module using a suitable connector. The AT
commands for the GSM modules have to be written in nesC.As we are
naïve to TinyOS and nesC, we have very little idea about the
conversion of the AT commands to nesC. Could you please tell us about
the feasibility of converting the AT command set to nesC, to send the
sensor data from one remote location through GSM modules.
Looking forward for your reply.
Thanks in advance.
--
Regards,
Sandhya
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