Background:
The system is for judging model airplane pylon races.
The judges in a race basically watch if the planes have crossed a point to determine how many laps have been completed and whether or not the airplane has gone beyond a pylon (marker on the race course) and therefore is not “cutting corners” of the race course.
For each judge station there will a Moteino based device for each judge at near ground level (lets refer to these as “judge ground stations”) that the judge will interact with (i.e. push a button or throw switch).
For each judge station there will be a Moteino mounted on a 10’ pole near the judge station (within 10’). Lets call that a “judge station repeater”
Three places need to know the action of the judges. Each of these are up to 600 feet from the judges station. At each of these there will be moteino on a 10’ pole (lets call this a “control unit repeater”) and a unit near the ground communicating to a light system (lets call this a “ground control unit”).
Two judge stations will have 4 judges, so 4 of the ground moteino units.
Two judge stations have 1 judge with one of the ground judge units.
So in total there will be:
10 judge ground stations (4 judges, 4 judges, 1 judge and 1 judge)
4 judge station repeaters
3 control unit repeaters
3 ground control units
For a total of 20 moteinos.
The area is generally flat open space but there can be some chain link fencing, shrubbery , chairs, tables and people at ground level.
In general, in response to a judge action a judge ground station will communicate to the judge station repeater (which will be listening to up to 4 judge ground stations) which will communicate to all 3 control unit repeaters that will each communicate to their corresponding ground control unit.
The information passed will be small, 4 bytes should be enough.
Actions will occur approximately every 6 seconds at every judge unit and could be near simultaneous (e.g. if two or more planes in the race cross the start finish/line at same or nearly the same time then the 2 or more judges at that judge station could initiate a communication at nearly the same time)
A race is up to 11 laps and approximately 1 minute long, so depending on the number of cuts there is approximately 100 total messages generated from the ground stations. Its less than 10 stations times 11 laps because some judge station do not have an action every lap.
Acceptable latency performance would be a delay between judge action and corresponding ground unit receiving the data correctly being less than 200 ms. Good to great would be less than 100 ms.
Acceptable reliability is that in 99.9% of races all messages get through successfully. Which means looking for 99.999% reliability of each individual message.
Seems like its doable using Moteino from reading threads and documentation and I would rather use it than Xbee because if nothing else than keeping track of all the Xbee product numbers, differences in API, firmware naming etc. gives me a headache plus this would be about $36/unit cheaper than Arduino FIO + Xbee option I am considering and I just think the Moteino is cool and like the transparency.
So my primary question is: Are my performance and reliability targets reasonable given the setup using 900 mhz RFM69HW?
Thanks,
Joe.