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Embedded Devices

Off-the-shelf products that can be used for Mesh-Seismology have a couple of requirements. Some of them are obligatory, some of them depend on the mode of operation and the seismological equipment that is to be used in combination with the devices.

We have followed a simple approach that guaranteed little development time (close to plug and play) and therefore allowed stable operability for field work in the early phase of one of our research projects (HADU, Hamburg a dynamic underground, BMBF), where a considerable amount of measurements had to be conducted.

This simple approach consists in the usage of a digitizer equipment that is supported by a ready-to-use plugin for the real time data acquisition software seedlink. Depending on the available plugin, either a serial communication (more common) or a ethernet connection needs to be established between the embedded device and the digitizer. Thus, one of the crucial requirements is the availability of at least one RS232 serial interface or an additional USB-port. Specific settings and eventual problems or pitfalls with the serial communication are documented for each device.

As the equipment is used in the field, power consumption plays an important role - the less power a device consumes the better it is (given the same functionalities). Usually, power is supplied by batteries in the field - most common is the use of 12 V Batteries. Therefore it is convenient to have a device which has an input voltage range around 10-14 V, else an additional (power-consuming) DC-DC module has to be used.

Certainly there should be a (at least one) mini-pci slot for hosting a WLAN card (802.11b/g). Here one should be aware that at some time in future one would like to use more powerful cards- then the power supply on the board must be able to fulfill the required consumption.

As some software should be installed on the device, flash memory should be not too tight. If you don't want to spend much time on optimization and thinking about what functionality you want to compile into your embedded OS image (probably OpenWrt), then you should think at least about 32 MB flash memory.

A USB interface is very convenient as it allows to attach low-cost USB keys as storage media. On one hand, this enables a redundancy backup of the data acquired and secondly you don't have to think too much about writing cycles of your compact flash card. All writing operations should then be done on the USB stick. Further, USB interfaces can also serve to replace or add additional serial interfaces using a usb2serial device drivers. In this way, one may use additional equipment (e.g. GPS for positioning) or digitizers that use USB for data connection instead of a RS-232 interface.

The following devices fulfill the minimum requirements specified above for mesh seismology and were available to us for use and testing. We try to maintain this list of embedded devices which can be used/operated as 'WAU'

Up to now, we have run the following device -- digitizer/datalogger combination:

check the above pages for detailed setup information and on-going developments