07 - VBOX Speed Sensor RS232/NMEA Output

The RS232 output is there to provide a connection to a computer so that you can configure the settings of the VBOX Speed Sensor in the VBOX Setup Software. The R232 output can also output NMEA format messages and the Racelogic Braketest format.

Protocol:

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

Message format:

$VB2100stttaaaaaaaaoooooooovvhhAAggGGcc
 

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;

end;

result:=CRC;

Protocol:

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

Message format:

$VBBTSTstttvvvvhhVVVVddddddddeeeescc
 

The header $VBBTST is in ASCII, the rest of the message is in hexadecimal.
 

Notes:

• The 32-bit floats are in Little endian format (low byte first or Intel format)
• The Brake distance number is in Big endian format (high byte first or motorola format)

CRC Calculation example:

s[n] is a string containing the message

Polynomial:= 4129 (0x1021)

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;

end;

result:=CRC; 

IMPORTANT - This is not available on the 5 Hz unit.

The VBOX Speed Sensor can output 6 types of NMEA messages, the most commonly used are GPGGA and GPVTG, the contents of which are shown below.
 

$GPGGA_hhmmss.ss_Latitude_N_Longitude_E_FS_NoSV_HDOP_msl_m_Altref_m_DiffAge_DiffStation*cs<CR><LF>
 

$GPVTG_cogt_T_cogm_M_sog_N_kph_K*cs<CR><LF>