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Talk-25: The iWhoiMicroModem MOOS Instrument

Dave Billin, University of Idaho

The University of Idaho Center for Intelligent Systems Research (CISR) employs a small fleet of autonomous underwater vehicles (AUVs) outfitted with Woods Hole Oceanographic Institute (WHOI) Acoustic Micro-modems. Efforts are currently underway to modify the navigation and control systems in these AUVs to use MOOS-based software. During the course of this work, it was found that existing MOOS software applications for interfacing with the WHOI Micro-modem are primarily concerned with acoustic networking, and thus expose only a small subset of the modem's functionality. This subset lacks two key features required by the CISR AUVs: 13-bit user mini-packets and LBL navigation pings.

To address the need for these features, a new MOOS application for interfacing with the Micro-modem was developed as part of a senior capstone design project. The result of this endeavor is the iWhoiMicroModem MOOS application: a MOOS instrument to provide comprehensive access to all of the Micro-modem's features. To minimize processing requirements while accommodating modem operations that can result in busy-wait times of several seconds, a multi-threaded software architecture was employed. Thread synchronization and signaling required the creation of cross-platform semaphore classes and an enhanced lock class derived from CMOOSLock to provide thread blocking with timeouts. Software was initially written and debugged under Microsoft Windows XP using Microsoft Visual Studio 2008, and was later built and tested under Ubuntu Linux by means of the CMake build system. Exchange of Binary data messages and user mini-packets was tested between a CISR AUV and a desktop computer connected to the Micro-modem.

In addition to exchanging binary and ASCII data messages, iWhoiMicroModem allows MOOS applications to access Micro-modem features such as mini-packet pings used for connectivity interrogation, interaction with LBL navigation transponders, local and remote control of hardware I/O lines on the Micro-modem, and support for a low-power sleep mode. A simple mechanism is provided to facilitate configuration of the Micro-modem's settings using parameters in a MOOS mission file. To assist in system evaluation and debugging, all diagnostic and informational messages optionally produced by the Micro-modem are published to relevant variables in the MOOS database. Two special accommodations for the CISR AUV implementation were provided. First, NMEA 0183 sentences forwarded from a GPS connected to the Micro-modem's auxiliary serial port are published to the MOOS database for consumption by a separate MOOS application. Second, an optional 'promiscuous mode' was added, enabling the modem to publish acoustic traffic addressed to other entities in the acoustic network.

The iWhoiMicroModem application has successfully demonstrated the ability to provide all functionality currently utilized by the CISR AUV. In-vehicle testing in the CISR AUV is currently underway as part of a larger integration effort, and is expected to be completed by September of 2010. Testing and debugging of modem features not currently used by the CISR AUV and those requiring a Micro-modem daughter board is the subject of ongoing work and is expected to be completed by August of 2010.

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Categories:

  • Acoustic Communications
  • UUVs
  • Academia