Proposal for a dataformat for communication between groundstations and their connected computers

Basically what I was thinking about was mostly the tracking of things, but I wanted to build a protocol in a way that the groundstations stay compatible for a deployment stage that enables them to send. This will surely not be the case for a while but still i'd like to think ahead. The main idea was that this kind of frame can be received and sent to the groundstation. For communication among groundstations over a satellite at least some kind of from adress field needs to be added.

Dataformat

Position	Length	Name	Meaning
0	32	magic	magic id = 4 bytes, 'HGG!'
4	16	protocol	protocol to be used in the payload
6	16	size	size of payload
8	32	chksum	checksum of payload (??)
12	16	modno	the receiving module that has generated this request
16	n	payload	payload goes here, variable size

No idea if a magic would be really needed. Basically it's a simple frame format that can be used to implement sending and receiving with the groundstations and should thus be capable of handling different stages in the project. The frames can bei either sent over a serial cable or other device types (like ethernet, firewire or anything else) but still allows to control hardware inside the groundstation directly.

Protocols

Here are a few possibilities

0 = Tracking (from = 0, rcpnt = own hw id)
1 = hardware ping (for finding out about other groundstations)
2 = groundstation diagnostics and control options
128 = Networking (Ethernet Frames go here)
…

RS-232 comunication

Hardware ideas

For instances where communication would need to be done via serial, there are several options available:

* WIZnet Serial-to-Ethernet Gateway - WIZ110SR uses an arduino processor to convert TCP/IP to serial and vice versa.
* Netmedia SitePlayer comes in two flavors, the SitePlayer Web Server and the SitePlayer Telnet. There are OEM version which can be added onto other projects/boards as well as stand alone modules that can be plugged into existing hardware. The telnet version can use TCP/IP to serial redirector software for communication or just a plain old telnet terminal. Built using the BasicX/Basic Stamp family of microcontrollers.

Software ideas

A good many options are available for as a software interface to the hardware presented above:

* HW VSP (Windows)
* ser2net (*nix)
* serialoverip (*nix)
* tcpser (*nix)

Using these hackable hardware devices and open or freely available software, a very slick TCP/IP to RS-232 interface could be created that allows remote acces, programming, etc. of satellite hardware or groundstation components to be made.