VBOX HD Lite Serial (RS232) Protocol

VBOX HD Lite Serial String Format

115200 Baud, no parity, 8 data bits, 1 stop bit

Message format:

$VBOXV$,nnnnffff,stttaaaaoooovvhheeezzxxyymmmcc

The $VBOXV$ and commas are in ASCII, the rest are in binary

	Format	Bytes	Description	nnnn, bit mask.
nnnn		4	Reserved to indicate channel presence (always 0x080003FF on VBOX HD Lite)
ffff		4	Status Flags Bit Description 4 Logging active 6 Media full 7 Media available
s	Integer	1	Satellites Number of satellites	0x00000001
ttt	Integer	3	Time Number of 10 ms ticks since midnight UTC	0x00000002
aaaa	Signed	4	Latitude (MMMM.MMMMM * 100,000) Signed Integer of Decimal minutes *100,000. Positive = North, Negative = South	0x00000004
oooo	Signed	4	Longitude (MMMMM.MMMMM * 100,000) Signed Integer of Decimal minutes *100,000. Positive = West, Negative = East	0x00000008
vv	Integer	2	Velocity Velocity in knots * 100	0x00000010
hh	Integer	2	Heading Degrees from true north * 100	0x00000020
eee	Integer	3	Height Altitude in metres WGS84 * 100 True signed 24 bit number	0x00000040
zz	Signed	2	Vertical Velocity Vertical velocity in m/s * 100	0x00000080
xx	Signed	2	Long acc (GPS) Longitudinal acceleration in g * 100	0x00000100
yy	Signed	2	Lat acc (GPS) Lateral acceleration in g * 100	0x00000200
mmm	Integer	3	RAM Address Free space on SD *980991 = Full, 0 = Empty	0x08000000
cc		2	Checksum CRC of message, See Note 1*

*Note 1

CRC Calculation example:

s[n] is a string containing the message

Polynomial:= 4129

CRC:=0;

for Loop:=1 to Length(s) do

begin

Temp:=s[Loop];

CRC:= CRC xor (integer(Temp) * 256);

CRC:= CRC mod 65536;

for i:=7 downto 0 do

begin

if ( (CRC and 32768)=32768) then

begin

CRC:= CRC *2 ;

CRC:= CRC xor Polynomial;

end

else

begin

CRC:= CRC *2 ;

end;

CRC:=CRC mod 65536;

end;

result:=CRC;