Home > VBOX Automotive > Speed Sensors > Single and Dual Antenna Speed Sensors > Speed Sensor User Manual > 08 - Speed Sensor RS232 / NMEA Output

08 - Speed Sensor RS232 / NMEA Output

The RS232 output is present to provide a connection to a computer for configuring the settings of the VBSS through Racelogic Config software. It also can output NMEA format messages or 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
ttt (MSB first) Time (ticks since midnight GMT, incrementing every 100mS)
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 0.01m/s per bit
gg 2 (MSB first) Lateral Acceleration, 0.01G per bit
GG 2 (MSB first) Longitudinal Acceleration, 0.01G per bit
cc 2 (MSB first) See Note 1 below

*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;

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
ttt 3 (MSB first) Time (ticks since midnight GMT, incrementing every 100mS)
vvvv 4 (MSB first) Velocity (ms -1)
hh 2 (MSB first) Heading*100
VVVV 4 (MSB first) Event velocity (ms-1) 
dddddddd 8 (MSB first) Brake Distance meters 
eeee 4 (MSB first) Event time seconds
s 1 (MSB first) Status 8 bits, bit 0 = brake trigger, bit 1 = brake trigger active
cc 2 (MSB first) See Note 1 below

*Note 1

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

 

The VBSS can output 8 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 Meters
Altref blank 48.0 m Geoid Separation  
M blank M   Units Meters
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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Last modified
10:49, 15 May 2015

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