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4.3 Observations

During many tests conducted in the process of projecting and creating Control

System I have noticed series of pros and cons. Some of them are to be revised and some

are not. In this testing report I will focus on issues significant in my opinion.

Lag

As expected in every wireless system visible lag occurs. In our case the time from

sending command from WCC software to receiving back confirmation of done task is

about 0.8 second. When we take into consideration that this data flows over WPA2-PSK

encrypted network it is not awfully long. To decrease this delay time we need to properly

optimize Arduino code.

Max servos

For the demonstration of the Control System I have implemented control over two

servomotors. In practice the only matters that limits number of servos are available pins

and power supply. In this case pins 10-13 are used by the WiFly shield to communicate

with Arduino over SPI. Second pin is used by the button and seventh by the LED. This

leaves us with total maximum amount of 6 servomechanisms. To extend this number

additional shield is required.

Status Indicators

Very useful solutions adopted in WiFly shield are the status indicators. To control

status just by taking a look over Control System three onboard LEDs are used.

Condition

PIO6 = RED

PIO5 = Yellow

PIO4 = Green

ON Solid

Connected over TCP

Fast blink

Not Associated

Rx/Tx data transfer

No IP address

Slow blink

IP address OK

OFF

Associated

PIO4, 5 and 6 are active high and can be connected to external LEDs to provide

network, connection and data status.

Range

In the tested prototype system wireless 802.11g network is used. As a specification

of the Wireless Router says indoor up to 100m and outdoor up to 400m range should be

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D-Link DSL-G684T Manual do Utilizador Página 54