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 Number of satellites used |
| ttt | 3 (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:
- 32 bit floats are in Little endian format (low byte first or Intel format)
- 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
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 | 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 | ||||