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5.4 Clocking calculations (receiver)
The following table (Table 12) indicates the relationships between frequencies where
the assumption is made that the camera frame rate is 1fps. The frequency at which
the system would then be set to run is denoted by f part which will be each component
part of the biphasic pulse forming the representation of the biological spike. In real
time each spike lasts 4ms and therefore each component of the biphasic spike will
last 1ms. That is the 1ms of the biphasic pulse represents an `on’ pulse of negative
polarity, 2ms of zero polarity and 1ms representing an `on’ pulse of positive polarity.
Derived from f part is f spike i.e. spiking time and finally f packet which is the frequency of
the AER packet i.e. pixel frequency. For completeness the periodic time for these
frequencies is also shown in the table.
fps T frame pix_count T packet T part
T spike
(T biphasic )(ns)
f spike
(f biphasic )
(Hz)
f part {Hz)
f packet
(Hz)
1 1 1024 0.00097656 9.76563E-07 3.90625E-06 256000 1024000 1024
1 1 256 0.00390625 3.90625E-06 0.000015625 64000 256000 256
1 1 64 0.015625 0.000015625 0.0000625 16000 64000 64
1 1 16 0.0625 0.0000625 0.00025 4000 16000 16
1 1 4 0.25 0.00025 0.001 1000 4000 4
Table 13 receiver calculations
5.5 Programming components descriptions
These subsections describe the following component parts: `Incoming(short) AER
stream’, `Production of colour data streams’, `Convert to `long’ format’, `Production
of output streams’ and finally `Formation of biphasic pulses prior to delivery to the
retinal implant’.
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