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RACELOGIC Support Centre

07 - VBOX Speed Sensor RS232/NMEA Output

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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.

RS232 Racelogic Data Format

Protocol:

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

Message format:

$VB2100stttaaaaaaaaoooooooovvhhAAggGGcc
 

Parameter Number of bytes Description
$VB2100 7 Header
S 1

Sats

Number of satellites used

ttt (MSB first)

Time

Ticks since midnight UTC, incrementing every 100 ms

aaaaaaaa 8 (MSB first)

Latitude

Double precision float 64 bit (radians)

oooooooo 8 (MSB first)

Longitude

Double precision float 64 bit (radians)

vv 2 (MSB first)

Velocity

0.01 knots per bit

hh 2 (MSB first)

Heading

0.01° per bit

AA 2 (MSB first)

Vertical Velocity

0.01 m/s per bit

gg 2 (MSB first)

Lateral Acceleration

0.01 g per bit

GG 2 (MSB first)

Longitudinal Acceleration

0.01 g per bit

cc 2 (MSB first) See CRC Calculation example below

 

 

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;

Brake Test Serial Data Stream  

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.
 

Parameter Number of bytes Description
$VBBTST 7 Header
S 1

Sats

Number of satellites used

ttt 3 (MSB first)

Time

Number of 10 ms ticks since midnight UTC, 24 bit unsigned integer

vvvv 4 (MSB first)

Velocity

(m/s), 32 bit IEEE float

hh 2 (MSB first)

Heading

Heading in degrees (0.01°), 16 bit unsigned integer

VVVV 4 (MSB first)

Event Velocity

Speed at last event (m/s), 32 bit IEEE float

dddddddd 8 (MSB first)

Brake Distance

Distance since brake event (m), 64 bit IEEE double precision floating point number

eeee 4 (MSB first)

Event Time

Time of event from midnight (seconds)

s 1 (MSB first)

Status Flag

0x01 for brake trigger, 0x02 for brake trigger active

cc 2 (MSB first) See CRC Calculation example below

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; 

NMEA Output

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>
 

Name ASCII String Units Description
Format Example
$GPGGA string $GPGGA   Message ID GGA protocol header
hhmmss.ss hhmmss.ss 092725.00161229.487   UTC Time Current time
Latitude dddmm.mmmm 4717.113993723.2475   Latitude Degrees + minutes
N character N   N/S Indicator N=north or S=south
Longitude dddmm.mmmm 00833.9159012158.3416   Longitude Degrees + Minutes
E character WE   E/W indicator E= east or W= west
FS 1 digit 1   Position Fix Indicator See Table 41
NoSV numeric 078   Satellites Used Range 0 to 12
HDOP numeric 1.001   HDOP Horizontal Dillution of Precision
Ms1 numeric 499.69.0 m MSL Altitude  
M character M   Units m
Altref blank 48.0 m Geoid Separation  
M blank M   Units m
DiffAge numeric   second Age of Differential Corrections Blank (Null) fields when DGPS is not used
DiffStation numeric 0   Diff. Reference Station ID  
Cs hexadecimal *5B*18   Checksum  
<CR> <LF>         End of message

$GPVTG,cogt,T,cogm,M,sog,N,kph,K*cs<CR><LF>
 

Name ASCII String Units Description
Format Example
$GPVTG string $GPTVTG   Message ID VTG protocol header
cogt numeric 77.52 Degrees   Course over ground (true)
T character T   fixed field True
cogm Blank     Course over ground (magnetic) Not output (empty)
M character M   fixed field Magnetic
sog numeric 0.004 Knots   Speed over ground
N character N      
kph numeric 0.008 km/h Speed  
K character K   K Kilometers per hour - fixed field
cs hexadecimal * 0B   Checksum  
<CR> <LF>         End of message
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