Ascension laserBIRD, Installation And Operation Manual

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laserBIRD™ Installation and Operation Guide
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Position/Orientation Data Format
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The Position/Orientation information generated by The Bird is sent in a form called a data record.
The number of bytes in each record is dependent on the output format selected by the user. Each
2-byte word is in a binary format dependent on the word type (i.e. Position, Angles, etc.). The
binary formats consist of the 14 most significant bits (bits B15 - B2) of the sixteen bits (bits B15 -
B0) which define each word. The two least significant bits (bits B1 and B0) are not used by The
Bird. The first bit of the first byte transmitted is always a one (1) while the first bit of all other
transmitted bytes in the record is always a zero (0). These "phasing" bits are required for the host
computer to identify the start of a record when the data is streaming from The Bird without
individual record requests. In general, the output data will appear as follows:
MS BIT LS BIT
7 6 5 4 3 2 1 0 WORD #
1 B8 B7 B6 B5 B4 B3 B2 #1 LSbyte
0 B15 B14 B13 B12 B11 B10 B9 #1 MSbyte
0 C8 C7 C6 C5 C4 C3 C2 #2 LSbyte
0 C15 C14 C13 C12 C11 C10 C9 #2 MSbyte
0 . . . . . . . .
0 . . . . . . . .
0 . . . . . . . .
0 N8 N7 N6 N5 N4 N5 N2 #N LSbyte
0 N15 N14 N13 N12 N11 N10 N9 #N MSbyte
The MS (most significant) bits are the phasing bits, and are not part of the data.
For example, The Bird is about to send a data record consisting of these three data words:
Word# Decimal Hex Binary (2 bytes)
MSbyte LSbyte
#1 4386 1122
00010001 00100010
#2 13124 3344 00110011 01000100
#3 21862 5566 01010101 01100110
The conversion to the binary data format by the Bird is as follows:
BIRD
1) Shifts each data word right
2) Breaks each word into MSByte
one bit LSByte pairs
MS LS 10010001 LS
00001000 10010001 00001000 MS
00011001 10100010 10100010 LS
00101010 10110011 00011001 MS
10110011 LS
00101010 MS
3) Shifts each LSByte right one more 4) Transmits all bytes in stream