Section: New Results
Interfacing artificial and natural parts through neuroprosthetic devices
Activating the neural system
This work has been developed in the context of the technological transfer we have began in 2005, with MXM.
A first prototype of external stimulator has been built: it corresponds to a DSU (Distributed Stimulation Unit) of our distributed stimulation architecture. This prototype is based on two ASIC (analog part of the DSU) and one FPGA (numerical part of the DSU). The numerical part contains the micro-machine (which executes the micro-program corresponding to the stimulus waveform to be generated) and the interface with the stimulus generator designed by the DEMAR team using HILECOP software  . As it embeds two ASIC, it allows to simultaneously control two quadrapolar electrodes.
A DSU programming environment (MedStim) has also been developed; it allows to graphically describe and to directly download stimulation sequences (pattern of stimulation) into the DSU component (FPGA part). Then the stimulation, executed on the prototype, can be programmed/started/stopped from the environment.
This prototype will be used for the experimentations to be performed in the "GENESYS" project. Security aspects, based on reference models, are currently studied in this project and will then be embedded in the DSU. We also work on the extension of the instruction set (micro-machine evolution) in order to generate more complex stimulus waveforms. Furthermore, based on the experimental results obtained on rabbits with the first ASIC, we have designed a modified enhanced version of the analogue part in 0.35 High Voltage CMOS technology. The circuit is currently under fabrication and will be tested in 2006.
Communicating between units
The protocol stack embedded in a DSU, including MAC (patented in 2004) and application levels, has been implemented on FPGA devices. A test platform is under development, based on a set of FPGA devices (DSUs) connected by means of an ethernet bus (that will later be replaced by a wireless medium). As the prototype of external stimulator (external DSU) we developed (cf. section § 6.2.1 ) can communicate on an ethernet bus, it will be integrated in the test platform which aims to study the global implanted architecture before developing specific hardware.