Odom ECHOSCAN, Руководство пользователя

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04/26/02 34
Revision 1.11
COMPUTER INTERFACE
Serial Output Strings
Serial output data rate from the ECHOSCAN SPU is 19.2 KBaud, updating
as fast as 13 times / second (depending upon the Range selected).
Output strings are ASCII binary and described as follows:
Data Description
Sync Header Four, 8-bit bytes (FFh, FFh, 00h, 00h) identifying the beginning
of the output string
Packet Type (10 or 01) Two 8-bit bytes (00h, 01h) identify the ECHOSCAN binary
output *1
Year (0-99), Month (1-12),
Day (1-31), Hour (0-23),
Minute (0-59), Second (0-
59) Six, 8-bit bytes - Year (00h-63h), Month (01h-0Ch), Day (01h-
1Fh), Hour (00h-17h), Minute (00h-3Bh), Second (00h-3Bh)
Sound Velocity (1200-
1700 m/s) One 16-bit word (Example: 04h B0h - 06h A4h) as set by the
operator on the LCDU
Latency (0-1000 ms) One 16-bit word (Example: 00h 00h - 03h E8h) indicating the
time lapsed between the sonar ping to the start of the fourth byte
in the output string
Sampling Rate (HZ) One 16-bit word representing the digitizing frequency
Range Samples / Beam
Quality Individual range readings (in No. of samples)*1
Range = Range Samples (Sound Velocity) / Sample Rate
2
Checksum One 16-bit word, unsigned sum of all 8-bit bytes excluding the
sync byte.
Table 7
ECHOSCAN Output String Format
*1 The ECHOSCAN string contains 30, 16-bit ranges for a total of 80 bytes and a transmission
time of 42 ms. Beam directions are in 3° increments, across Port (Beam 1) to Starboard (Beam
30). Beams 15 and 16 are each 1.5° off nadir. The most significant 14 bits of each range
represent the round trip travel time in samples. The 15th and 16th bits (least significant)
indicate beam quality, i.e., 00b = bad, 01b = low signal strength, 10b = out of sequence, and
11b = good.