A High Speed USB Digital Pattern Generator and User Interface to Operate a Wireless Implantable Neural Microstimulating System Jim Simpson, Frankie Myers, and Chris Thomas Electrical and Computer Engineering, North Carolina State University, Raleigh, NC 1. MOTIVATION 2. USB INTERFACE 4. EXPERIMENTAL RESULTS 3. INTERFACE IMPLEMENTATION Illinois Institute of Technology Interstim-2B is an existing 64-site highly versatile microstimulator system powered and controlled through an inductive serial wireless link. In this project we have developed: A high-speed interface hardware between any USB-compatible device such as a PC or PDA and Interstim-2B with data rates up to 24 Mbits/s Firmware to operate Cypress EZ-USB FX2 family of USB microcontrollers Custom USB 2.0 device drivers for interfacing with Windows operating system High data throughput algorithms in C++ to support a visual prosthesis system User-friendly software environment in C++ for physiologists and neuroscientists Elimination of any costly commercial software or hardware  Hardware: We chose the Cypress CY7C68013 EZ-USB FX2 microcontroller because: Supports USB 2.0 high-speed at 480 Mbits/s Low cost ($15/chip) and popular hardware Bus powered (no need for additional supply) Extensive Documentation and C++ API’s General Purpose Interface (GPIF) A 2” × 2.5” 4-layer PCB was designed which contains: USB microcontroller USB port EEPROM to store the firmware for plug & play operation 3.3V Power regulator 24 MHz clock oscillator I/O connectors Decoupling capacitors Prototype Interface Setup with Interstim-2B Custom Designed PCB The General Programmable Interface (GPIF) is a micro-coded state machine, which automatically transfers incoming data to the output pins without involving the Cypress on-chip microcontroller. 6. CONCLUSION We successfully demonstrated: Continuous data transmission at 6 Mbits/s Burst Data transmission at 24 MBits/s Sent Interestim-2B 19-bit command frames at 1,000,000 Frame/s FSK modulation in software with user selectable patterns Each biphasic pulse takes a minimum of 4 command frames to generate Generated approximately 79,000 continuous pulses per second. Burst data transfers at 24 Mbps Continuous transfer at 6 Mbps High-Speed data transfers in the range required for a visual prosthesis application is indeed possible with the developed USB interface.  Firmware: 5. FUTURE WORK Operate Interestim-2B through its inductive wireless link Develop a prototype for visual prosthesis demonstration using this USB interface along with a camera and PDA. Extend the USB interface to other implantable devices. Extend the USB interface to support the cure for a variety of pathological diseases. Changes in light transmittance evoked by electrical stimulation in slices prepared from mouse somatosensory cortex was recorded using Intrinsic optical signal (IOS). Firmware structure FX2 Microcontroller Block Diagram showing GPIF path Final interface prototype 10 nF Capacitive, 10 ms discharge, pulses at 60 Hz, Q  40 nC Extracellular ion conc. changes Tissue sample at 400x Advancements in neuroprosthetics are leading the way forwards in the restoration of lost sensory modalities such as hearing and vision. These implantable microelectronic devices call for: Wireless, Wideband, Portable, Reliable, Highly Flexible, and Universal communication medium to interface external artificial sensors such as microphones and cameras to devices implanted inside the human body. Interstim-2B with microelectrodes University of Southern California Faculty Advisor: Dr. Maysam Ghovanloo Acknowledgements We would like to thank the NCSU Undergraduate Research directorate for supporting this project. We also like to thank the Electrical and Computer Engineering department for providing us with the lab space and equipments.  Software: Implanted Microstimulator USBInterface ExternalDevices The size of the device can be further shrunk to make it even more flexible. The interface is versatile enough to be used for interfacing with almost every implantable device. Parses serial data from a script file which stores the interstim-2B commands and stores it as a data structure UML Diagram of User Interface Software Custom User Interface: Developed in Visual C++.NET Utilizing Cypress device drivers