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A Prototype Optical Tracking System Investigation and Development - page 69 / 170

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5.2 Device selection

55

to produce complex high level modules and could be used to build very fast algorithmic blocks for the camera module. soft core processor is a processor that is embedded into the logic elements of the FPG . Standard C code can be executed on the soft core and custom blocks can be executed from the C code [74]. This allows very specific optimisations to be made by implementing some algorithms using the FPG ’s programmable hardware and developing other parts in software. This approach is powerful as it fuses the speed of a hardware based approach with the flexibility of a software approach. lthough this method has great potential it was discarded as it was felt that the learning curve for using

an FPG

could be greater than other methods considering the author’s experience with

these devices.

5.1.2

Image sensor with low power general purpose microprocessor

nother option was to connect a low power general purpose processor (such as a micro-

controller based around an

RM core) to an image sensor, however, this approach was

discarded as it was thought that many low power processors do not have the processing

power required.

lso, many microprocessers do not have suitable peripherals to allow

connection to image sensors.

5.1.3

Image sensor with DSP

final option was to use a DSP and connect this directly to an image sensor. This allows the performance of DSPs to be leveraged. Careful choice of DSP is required, however, to

find a DSP that can be connected directly to an image sensor.

Blackfin DSP from

nalog

Devices Inc. was chosen. The choice of model is described in Section 5.2.1.

5.2

Device selection

The option chosen was to use a DSP connected to a CMOS image sensor using either ex- ternal SDR M or only internal SR M. DSPs are well suited to processing large quantities of data quickly and often have special instructions to make processing more efficient that standard microprocessors do not have. Using a DSP is a good compromise over using custom hardware blocks programmed into a FPG .

5.2.1

DSP selection

The Blackfin family of DSPs from sit somewhere between traditional

nalog Devices Inc. were considered. Blackfin DSPs DSPs and general purpose standard microprocessors.

They have many of the instructions found in traditional DSPs such as a one clock cycle mul-

tiply

and

accumulate

operation

but,

unlike

more

traditional

DSPs,

contain

an

abundance

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