Echo Sounder Data Format Description

April 17, 2020 06:13

This is a post based on a support request sent in to support@nortekgroup.com

I’m working with a Signature 100 with echo sounder, and are getting a coding error when I try to read the header file; expecting 0xa5 as described in the "System Integrator's Guide" but found 0xbf.

Comments

1 comment

Martin Alvsåker

April 17, 2020 07:24
The Signature 100 with Echo Sounder introduces a new usage of the Data Headers. The Echo Sounder RAW data packets can be big. Hence the 16-bit Data Size of the standard (10-byte) Headers is not enough. A variant of the Header (12-bytes) is used:

Packet Header Definition
```
typedef struct
{
   unsigned char  sync;         ///< = 0xA5
   unsigned char  hdrSize;      ///< = sizeof(CommandHeader_t) = 12
   unsigned char  ID;           ///< Record ID (data type)
   unsigned char  family;       ///< bits 4-7 = instrument type/family, bits 0-3 unused
                                ///< (instrument dependent)
   unsigned long  dataSize;     ///< Size of data block to follow
   unsigned short dataChecksum; ///< Word-wise checksum of data block
   unsigned short hdrChecksum;  ///< Word wise checksum of this structure
} CommandHeader2_t;
```
The Echo Sounder RAW format uses the following Record IDs to store data:

0x23 RECORD_ID_ECHO_RAW Echo Sounder raw sample data format
0x24 RECORD_ID_ECHO_RAW_XMIT Echo Sounder raw synthetic transmit pulse data format

Echo Sounder RAW Data Record Definition

The Echo Sounder RAW Data Record consists of a Data header part followed by a Data part.

Data Header Definition

Data Definition

The Data consists of an array of nComplexSamples Samples. Each Sample is of type Complex Fract32:
```
typedef struct {
   fract32 re;
   fract32 im;
} complex_fract32;
```
The fract32 type represents a single 32-bit signed fractional value. The Range of the value is [-1.0,+1.0).
0

Comment actions Permalink