Nortek Signature Series Manual

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Nortek Signature Series Manual Manual pdf 8 page image

Integrator's Guide8© 2017 Nortek AS3 InterfacesIn addition to the traditional serial port interface for real time data output there are severaloptions for communication over Ethernet. The Ethernet communication is handled by a dedicatedprocessor in the instrument. This network processor runs a Linux operating system, which makesit possible to connect to the instrument via telnet, raw connections and FTP. The networkprocessor mainly provides Ethernet connectivity. The other processor in the instrument, calledthe Doppler processor, is where the commands end up and where they are used to perform themeasurements as specified.The concept of a telemetry file has also been introduced which can be utilized in several waysdepending on the chosen interface. Below are some details:3.1 Command interfaceThe command interface makes it possible to communicate with a Signature instrument usingterminal software, the serial port and a set of commands. The interface is also available overTelnet. Some highlights:ASCII based and line oriented. Commands are terminated with CR/LFOptional capsulation of commands using NMEA style prefix and checksum to ensure dataintegrityNMEA style commands will return argument names in their responseArgument limits can be retrieved through commandsComprehensive validation and error handling is implemented.Invalid configurations return the erroneous argument with limits directly, so that eachsubsequent error can be handled until a valid configuration is achievedA single command can be used to retrieve the complete configuration of the instrument withoptional output to fileCommands to set default parametersExternal controllers can use commands to store data in the raw data file (e.g. GPS position)3.2 TelemetryOur use of the telemetry term implies a "subset transfer system", that is, storing a subset of datafor transfer over low-bandwidth links (for example over iridium links, acoustic modems, etc). Thetelemetry file is typically used in cases where the integrator either does not have the processingpower or bandwidth (if only a low data rate serial port is available) to do the processingthemselves.For online data transmission a versatile scheme for telemetry options is available. The telemetryfile can be read out over the serial interface either in chunks or as a complete file while checksumor CRC on the downloaded data can be applied in a configurable manner. This enables externalcontrollers to configure separate handling of all, or a subset, of the measured data. That meansthe file can be output directly as they are ready, or the data can be stored to a telemetry file forlater retrieval. The data format can be selected from a number of formats, including both binary