Advanced Rowing Instruments – Business Plan & Final ... - Saket Vora

an 8-bit or higher analog-to-digital converter. Microcontrollers by their nature have digital I/O
pins. These are the only two features that the Mercury model requires.
Feature Mercury Titan
Digital I/O • •
A/D • •
MAC •
SPI •
USART •
Table 4.1: Required processor features.
Because of its increased feature set, the Titan model has a more stringent set of requirements.
Most notably are its off-chip peripheral communication interfaces. This microprocessor must have
a number of standards built in for ease and efficiency of use. Both Serial Peripheral Interface
and Universal Synchronous Asynchronous Reciever Transmitter (USART) must be implemented
for Secure Digital and Bluetooth, respectively. In addition for the more advanced analysis, such
as real-time velocity calculation, a Multiply Accumulate Unit must be included in the processor.
This will allow for the integration and filtering processes to be completed.
4.8.3 Processors Considered
A number of processors were considered for the ARI devices. These included product offerings
from TI and Microchip. Ultimately, Microchip was selected. Datasheet samples for considered
processors can be found in the appendices.
Texas Instruments Two processor lines from Texas Instruments were considered. The C54xx
and C55xx processor types were both examined for possible use. A development kit for the C54xx
had been previously ordered. Unfortunately, the C54xx did not have an A/D module built it.
Because of power concerns, this model was discarded. In addition a large amount of supporting
circuitry was necessary and as such these processors were overlooked. In future development, the
C55 should be closely examined, however, because it has native SD support.
Microchip Microchip was selected for the Mercury model because its development kit was relatively
inexpensive and readily available. The PIC18F4520 was selected as the primary processor
for the Mercury. It had the necessary features for both Mercury and Titan with the exception of a
MAC . In addition, Microchip offers DSP products that are mostly compatible with code written
for the PIC18. Therefore, when the Titan comes under development, existing Mercury code can be
easily ported to the new processor for new functionality on a shorter software development cycle.
Products offered by other compaines were not as easy to integrate in a short time, nor were they
able to meet the develoment cost profile necessary. Most other processor offerings also required
external crystal oscillation, increasing layout complexity. Becuase of the short development cycle,
this was undesirable.
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