Hobby sites like sparkfun.com and lipoly.de sells a wireless fob for the 2.4 GHz band that fits the bill nicely with 5 buttons and a programmable Atmel ATtiny 24 on board. On the receiver end, another Avr talks to the receiver radio and the Seatalk bus.
The 5 available buttons may be laid out like:
- Left: Port 1 degree
- Mid + Left or Up: Port 10 degrees.
- Right: Starboard 1 degree
- Mid + Right or Down: Stb. 10 degrees.
- 2 Mid presses followed by left/right within 3 secs: Tack 100 degrees.
This will be given as 10x10 degree commands on the bus to suit all pilot types.
- The receiver Avr will listen on a uart for GPS XTE (Cross track error) NMEA commands.
- A switch will determine whether these should be used for driving the autopilot from the active route in the GPS.
In addition the remotes can be used as MOB FOB's:
- The att24's watchdog is used to wakeup the uC and send a keepalive message every 30 secs.
- If the signal does not arrive (because the FOB drowned by going overboard) the receiver will issue an alarm as for the AIS SART.
- Some kind of procedure for signing the FOB's in and out needs to be devised. ??
Maybe provide a USB socket (In AVR Firmware) (com port) and and a windows app?
- When reproprogramming the att24 in the FOB, a serial number must be flashed in.