- General Microservers, Vexcel Microservers, Quick Reference, Data Acquisition, Middleware
- Components GPS, SBC
- Configuration Microserver, SBC, SD Card, Power
- Operation Communication Protocol (SBC <--> uc), SBC Operations, Agent
- Operation (background) Task Manager "milo", config files, MACRO
- Microcontroller Microcontroller, Firmware, Skeleton firmware
- Evaluation 2008 Cairn relay failure evaluation, Lab evaluation, Eval-Firmware, BPMS, Source notes
- PCS Board PCS Board Design, Voltage Monitoring Circuit
- Gen 3.1 Kernel Upgrade and Field Notes (Spring 2007)
- Gen 3.1 Microserver, README, Schematics
- Gen 3.1 Task Manager "milo", GPS, Firmware
Vexcel Microservers (VuS) are simple rugged computers with radio modems that can survive and operate outdoors in harsh environments like Antarctica. They are called Microservers because of their networking capabilities, particularly as they can act as anchor points for localized lightweight sensor networks built on motes. They also function as network nodes in a typically ad hoc configuration.
Below we give a short use-scenario followed by an overview-list of Microserver specs and capabilities. We next describe the current status of these devices and then give a some more detailed concepts for operation. These "con-ops" are intended to give a sense of the types of problems the Microserver design addresses across several areas: primarily power, data, communication, and support for both external sensors and local sub-networks.
This scenario is an extrapolation from our research in SEAMONSTER and some related projects in the polar regions.
Suppose we have five Vexcel Microservers (abbreviated VuS) and sufficient resources (batteries, photovoltaic panels, mounting hardware, undergraduates, helicopter time, steam drill) to do a field deployment on Taku Glacier in Southeast Alaska. Four units are drilled into the glacier center-line by means of steam drilling holes, sinking conduit tripods, and anchoring the VuS and power supplies to this. The fifth VuS is anchored on a glacier-margin rock and connected to a 900MHz Freewave radio which also receives power from the VuS. The Freewave radio is used to communicate data in both directions across a 20 km hop to the Natural Sciences Research Laboratory in Juneau.
One glacier VuS is coupled to a PTZ webcam by means of an internal Ethernet switch. All four of them, in addition, carry internal sampling boards for digitizing 3-axis geophone signals. These are used to record ice-bound acoustic signals, for example from calving events. Each unit also creates a time-series record of its position by means of an on-board GPS. Hence visual records, seismic signals, and glacier dynamics are all being recorded. In the case of the seismics, the VuS single board computer performs continuous thresholding and preserves only interesting seismic signals, not the quiet intervals in between.
All five VuS units also receive data over serial-port connection from a cluster of weather-station instruments recording precip, temperature, wind speed and direction, humidity, barometric pressure, solar illumination and ground-reflected illumination. This creates five parallel storylines about the local meteorological conditions.
While the system operates continuously in summer, in autumn as sunlight fails it reverts to a limited duty-cycle schedule, first with three, then two and then only one operational interval per day. In between these intervals the entire system is turned off except for a timer chip running on only microwatts of power. When it is time to wake up, the battery voltage is checked prior to re-start to ensure there is enough energy available. If during an operational interval the supply voltage drops below a threshold, the main computer is signalled to halt operation. It shuts down and then the system goes into a hibernate/check-voltage cycle until sufficient energy is charged back into the main battery supply to continue operation.
During operation the system is continuously building Return Datasets that are transmitted by WiFi to the stationary VuS. It in turn transmits these data bundles back to the NSRL where they are unpacked into a relational database. This database may be queried over the Internet providing near-real-time access to the data stream as it is acquired.
- Size: 14 x 11 x 7 inches or 36 x 28 x 18 centimeters
- Weight 4kg
- Enclosure: Thick durable plastic case (not "pelican" plastic) with O-ring seal.
- Rated NEMA-4X (all-weather-resistant, non-immersible)
- Two extruded rails available along opposite edges of the base for mounting holes
- Lid is screw-down for durability in installation and to discourage easy tampering
Through-enclosure-wall connectors: Mil-spec with caps
- One N-type antenna connector: WiFi
- One N-type antenna connector: To internal GPS board
- One N-type antenna connector: Local wireless network (e.g. 802.15.4) or other applications
- One power input for External 12 V (e.g. gel cell)
- One power input for Photovoltaic supply
- One power output for driving externa devices (4-pin: 12V/5V/3.3V/Gd)
- One Ethernet pass-through
- One USB pass-through
- Two general-purpose 9-pin pass-through connectors suitable for analog (geophones), serial.
- Grounding lug
- Single Board Computer
- ARM-9-based Technologic Systems TS-7260
- Boots TS-Linux by default from 512+MB SD card
- Will also boot Windows XP-embedded (in development)
- Can be configured to run at 1/4 watt power consumption
- Supports 2 USB ports, 3 serial, Ethernet, PC/104 bus
- Default is 802.11G
- Standard device is a Wireless Ethernet Bridge (LinkSys WET 54G)
- Room in case to substitute a wireless router, e.g. LinkSys WRT 54G
- RF output runs through a 1 watt 2.4GHz signal amplifier to external antenna connector
- Best range to date: 15 kilometers line-of-sight between two 46 cm omnidirectional antennas, 200kbps.
- Novatel "Superstar II"
- Records L1-Carrier Phase; can achieve (advertised) decimeter-scale precision location fixes.
- Greenland field testing: Differential processing with some time averaging gave precision of ~10 centimeters in the vertical component.
- Novatel "Superstar II"
- Power Conditioning
- Custom power control board driven by low-power PIC microcontroller
- Powered independently for 2 years of operation from internal LiSO2 batteries
- Senses external supply voltage, if low: Hibernates for a recovery interval, checks again.
- Carries a byte-wide communication channel to/from the Single Board Computer
- Independent control of each (internal and external) power supply (see Standard Operation below).
- The device is designed with additional internal space. There is room for...
- One or two additional circuit boards
- As noted a WRT 54 router board can be installed
- A high-frequency sampling board can be installed
- A mote base station
- The extra antenna feed can be used to increase range to a mote sub-network
- One or two additional circuit boards
- External supply provides 12 Volts plus (optionally) Photovoltaic for recharging
- Internal to enclosure: SunSaver charge controller will recharge the main battery automatically
- Hibernation power consumption: negligible
- Running full-bore: 7.2 watts total consumption (600 mA) with no external loading
- 3.5 watts is a good "normal operation" power consumption estimate (by means of WiFi duty cycling).
- By-component breakdown follows
- 2.5 watts: Single Board Computer
- ARM-9-based SBC runs at 133MHz
- Current: 210 milliamps
- Power draw can be reduced to 0.25 watts (See How to get by on under 1 watt)
- 0.5 watts: GPS board
- 1/2 watt is nominal power consumption at 3.3V. 60mA most recent measurement (0.7W).
- 3.1 watts: Wireless Ethernet Bridge
- 260 mA most recent measurement
- 0.5W 1/4-watt 2.4GHz Amplifier
- 40 mA most recent measurement
- Measurement needed for 1W amplifier
- 0.4watts: Support electronics
- 30 mA most recent measurement
- Updated measurements are needed for the current VuS rev
- Base mote support power draw estimate needed
- USB Thumb Drive access power draw estimate needed
Current Status and Cost
- Generation 3.2 has gone through prototype evaluation and an initial build of 16 units distributed among Vexcel, University of Alaska, Vanderbilt, and Copenhagen.
- The configuration and operation of the Gen 3.2 Microserver is documented on these wiki pages, particularly per the directory listing at the top of this page.
- During the current development phase these devices are purchased directly from the manufacturer (KimCo).
- The Gen 3.2 device runs about $3800 per unit with price breaks for larger quantities.
- If you have an interest in these devices please contact (Rob Fatland: rob at robfatland dot net).
Generation 3.1 has been built out to approximately 20 devices and these have been variously deployed in Greenland and the Canadian Arctic.
Standard Operation Concept
- Configure the Vexcel Microserver Single Board Computer based on an operational plan.
- This includes a Task Manager or Agent program that runs on boot.
- Place a Vexcel Microserver in a remote location
- Adjacent: Place an energy source such as a lead-acid battery adjacent, join by power cable.
- Adjacent: Place a recharge supply such as photovoltaic panels, join by power cable.
- Install other external instrumentation. Instruments may be powered from the microserver Power-Out port.
- Install communication and GPS antennas.
- Turn the device on, verify operation, and depart.
The device can -- in principle -- operate for up to two years as a data acquisition / processing / relay station. Power conservation through component management and duty cycling is handled by the SBC Agent. Data recovery can be by means of 802.11G WiFi, site re-visit, or alternative communication methods such as satellite modem. The device can support a "Mote" sensor sub-network and can support one or two USB "thumb drives" for 8GB of data storage.
In short the microserver is intended to adapt to a wide array of operational scenarios, solving the energy-cost-data problem by providing a flexible platform.
Vexcel Microservers were developed with NASA STTR support beginning in 2002 in collaboration with Penn State University. They were conceived as high-frequency seismic recording devices with extensibility to many other types of sensors.