[drats_users] Arduino and D-RATS

[Dan Smith]

>      I was talking with Dan a few weeks ago about sending the GPS
> coordinates from an Arduino microprocessor and getting the results to
> display on the map. He also recommended that I post on this mailing
> list to discuss the solution. I now also need the capability to send
> text to the IM interface of D-RATS. I've been able to output a
> message sent from D-RATS into HyperTerminal and what I concluded from
> that is that there is some type of message ID and checksum value that
> needs to be calculated upon transmission of the message and a check
> on the receiving end of the message. I'm working on a homing system
> for firefighters that sends the GPS results to the map screen and
> sensor data to the IM screen. Could someone fill me in on how this
> checksum works? Thanks for your help.

There's more than just a checksum, there is some framing on either end
of the packet, as well as multiplex information (similar to what a
normal network stack provides.

Most of what you need is found here:

http://d-rats.com/hg/hgwebdir.cgi/d-rats.hg/file/021203b75329/d_rats/ddt2.py

In the get_packed() method, you can see the structure of the frame. It
starts with a magic number, a sequence number, a session number, frame
type, checksum, length, address information, and finally the data.
Either end is capped in an [SOB] and [EOB].

The information you need for the type to use for the various chat
traffic is here:

http://d-rats.com/hg/hgwebdir.cgi/d-rats.hg/file/021203b75329/d_rats/sessions/chat.py

Since D-STAR radios are not 8-bit clean, there is also escaping that
needs to be done, the algorithm for which you can find here:

http://d-rats.com/hg/hgwebdir.cgi/d-rats.hg/file/021203b75329/d_rats/yencode.py

Hope that helps!

-- 
Dan Smith
www.danplanet.com
KK7DS
-------------- next part --------------
A non-text attachment was scrubbed...
Name: signature.asc
Type: application/pgp-signature
Size: 490 bytes
Desc: not available
Url : http://intrepid.danplanet.com/pipermail/drats_users/attachments/20130112/b38959f0/attachment.bin