Retinal Prosthesis Dissertation - Student Home Pages

Membrane potential (mv)
+30
0
-70
0 1 2 3 4 5
Time(ms)
Peak to peak 100
x 50 pulses equal 5v
Figure 56 AP propagating through optic nerve
6.6 Pre processing
Presently the incoming image for this prototype system is held in ROM, prior to full
implementation a camera would be interfaced to the FPGA, either a RGB camera or
a YUV camera utilizing an intellectual property (IP) core to convert to RGB signal
format. Future work could encompass the possibility of converting a camera with
universal signal bus (USB) protocol to RGB format. When using an RGB or YUV
camera the frame rate to be set will be determined by the partial_spike_clock
frequency derived from the FPGA clock frequency. The ratio is largely determined
by the image size to be transmitted e.g. for a circa 1000 pixel image a
partial_spike_clock frequency of 25Mhz would expect a frame rate of 25fps and
similarly a partial_spike_clock frequency of 50Mhz would expect a frame rate of
50fps for the same size of image.
6.7 Future work
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