The Ground controller (Ground) and KAP rig controller (Air) communcate via radio modems (APC220). This results in a 9600Bd half duplex serial link.

Ground and Air comminicate by transmitting short human readable messages which are comma separated records of items. The messages have the following layout:

message: $ + item  + [,item] + \n
item:    ID + value
ID:      2 characters, 
         upper case for commands and settings,
         lower case for status an mesurments
value:   integer value
example:  $PM2,VM0,gv123\n

White space in messages is ignored. The following IDs ar used

gv  gv1134  Ground battery Voltage in [v/100] here 11.34 volt
av  av732   Air battery Voltage in [v/100]
MP  MP120   Manual Pan setpoint [deg], right is positive
MT  MT10    Manual Tilt setpoint [deg], down is positive
MC  MC17    Manual Click counter (change -> take picture)
cp  cp120   Current Pan value [deg], right is positive
ct  ct10    Current Tilt value [deg], down is positive
cc  cc17    Current Click value (change -> take picture)
VM  VM0     Video Mode (0:off, 1:on)
PM  PM2     Pan Mode 
                0:Manual, 
                1:Auto KAP, 
                2:Panorama,
                3:Smart (Manual, Autokap after 60 sec of inactivity)
TM  TM1     Time Mode 0:Manual, 1:quick, 2:2s, 3:3s, 4:5s, 5:10s
vm, pm, tm:  current status in Air