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General / SerialDataFormat

Serial Data Format

Introduction

Data is in the same format in both the live serial stream and as stored on the compact flash card. However, not all messages are sent in both formats depending on the configuration of the system.

All messages are in the same format:

Header bytedata1data2data3...dataNchecksum

The header is a single byte, the data length is between 1 and 255 bytes depending on the type of message and the checksum is a single byte which is calculated from the sum off all bytes including the header. In the typical case where the checksum is greater than 255, then only the least significant byte is stored.

Note that since the data stream is binary, there is not possible to have a "unique" header available before each message - as such the data has to be decoded continuously to ensure that correct messages are extracted. For example if we start decoding a stream and we get a value of "9" for the first byte, we can see from the table below "message type 9" is 5 bytes long, so we wait until we get another 4 bytes; and then check the checksum. If the checksum is correct then it is likely (1 in 256) that this was a "type 9 message" and we move onto the next message to decode. If the checksum was incorrect then we use the 2nd byte as the message header and check its checksum and so on. It is unlikely, but possible to get incorrect messages decoded when we first start decoding the data stream however the chances rapidly decrease with just a few messages.

  • After decoding 1 message in a row without error there is a 1 in 256 chance of an incorrect message
  • After decoding 2 message in a row without error there is a 1 in 65536 chance of an incorrect message
  • After decoding 3 messages in a row without error there is a 1 in 16million chance of an incorrect message

The following table gives summary information on the range, resolution and units used for some common serial data channels. For more information refer to specific channel pages.

Channel type Range Resolution Unit
External temperature channel -3276.8 3276.7 0.1C C
External pressure channel 0 - 65535 1mB mB
External frequency channel 0 - 6553.5 0.1 Hz Hz
External time channel 0 - 65535 1ms ms
External auxiliary (percentage) channel -3276.8 - 3276.7 0.1% %
External angle channel -3276.8 - 3276.7 0.1o Degrees
External Miscellaneous channel 0 - 655.35 various -
Yaw / Pitch / Roll rates -327.675 327.68 0. 01o/sec Degrees/s
Accelerations X/Y/Z -127.996 127.996 1/256g g
Voltage 0-65.535 1mv v


Serial Physical Layer: For most products the default data rate is 115200 baud, RS232 levels. 1 start bit, 1 stop bit, no parity bit(s), no handshaking.

Message IndexLengthDescription
19Run Informtion
211Run start/stop info
3VRaw GPS Data Input
47New Sector Time
521New Lap Marker
66Logger Storage Channel
76GPS Time Storage Channel
86Accelerations
95Time Stamp
1014GPS Positional Data
1110GPS Raw Speed Data
123Beacon Pulse Present
145Frequency 1
155Frequency 2
165Frequency 3
175Frequency 4
185Frequency 5
19VSerial Data Input
204Analogue 1
214Analogue 2
224Analogue 3
234Analogue 4
244Analogue 5
254Analogue 6
264Analogue 7
274Analogue 8
284Analogue 9
294Analogue 10
304Analogue 11
314Analogue 12
324Analogue 13
334Analogue 14
344Analogue 15
354Analogue 16
364Analogue 17
374Analogue 18
384Analogue 19
394Analogue 20
404Analogue 21
414Analogue 22
424Analogue 23
434Analogue 24
444Analogue 25
454Analogue 26
464Analogue 27
474Analogue 28
484Analogue 29
494Analogue 30
504Analogue 31
514Analogue 32
5267Channel Data Channel
5311Display Data Channel
546Reflash Channel
5510Date Storage Channel
5610GPS Course Data
5710GPS Altitude and Speed Accuracy
5811Extended Frequency 1
5911Extended Frequency 2
6011Extended Frequency 3
6111Extended Frequency 4
6211Extended RPM
633Start of Run Channel
645Processed Speed Data
6530Gear Set Up Data
66|11Bargraph Set Up Data
674Dashboard Set Up Data
684Dashboard Set Up Data Two
6942New Target Sector Time
7042New Target Marker Time
713Auxillery Input Module Number
725External Temperature Channel
735External Frequency Channel
745External auxillary channels
756External Time Channel
7624New LCD Data Channel
773New LED Data Channel
786Pre Calculated Distance Data Channel
794Yaw Rates Channel
804Calculated Yaw Channel
815Pitch Rate Channel
825Pitch Angle Channel
835Roll Rate Channel
845Roll Angle Channel
8510Gradient Channel
865Pulse Count 1
875Pulse Count 2
885Pulse Count 3
895Pulse Count 4
906Baseline Channel
915Unit Control Channel
924Z Acceleration
935External Angle Channel
946External Pressure Channel
955External Miscellaneous Channel
9610Time in to current lap and sector
978High resolution event timer
98 Not Used
99 Not Used
100 Not Used
10119Sector Definition Channel
102VBRAKEBOX to PC Communication Channel
10317DVR Communication Channel
1049Video frame index
10511Local NED velocities
106 Not Used
107VGeneral Configuration Message
108 -255 Not Used
Page last modified on August 21, 2015, at 07:37 AM