User manual

ECE 477 Final Report Spring 2004
in its memory map. Low power consumption is the key feature to interrupt driven programs, and
important for the battery driven wireless device.
Coding the base station will also be interrupt driven, simply because most of the time it
will be inactive. After initialization, the base unit will wait for one of two events. The first is an
interrupt from the RF module, which will cause the processor to buffer the whole string and then
pass that string through to the computer along the serial port. The second event is a signal from
the serial port, which the unit will pass directly through to the RF module along its serial data
line after switching to “transmit” mode.
Software Design Narrative – Base Module
RF Interrupt
The RF interrupt routine is crucial to the task of receiving an order to display it on the
computer. The function will be relatively simple. The first step after running the routine will be
to store the character received in a string, which will act as a buffer. At each clock pulse from
the RF unit, a new character will be stored on the buffer. When the terminating character is
received (in our case, ‘+’), the program will then open the line to the serial port and send the
string through. The unit will then go back to sleep until the next interrupt.
Serial Interrupt
A serial interrupt will mean that the base computer is trying to send a new page of
memory map to the wireless units. When this happens, instead of allocating a string, the unit
will send the character straight through to the RF device and toggle the clock signal. The unit
will then go back to sleep.
Software Design Narrative – Mobile Module
RF Interrupt
An RF interrupt on the mobile module means that the base computer is trying to send a
new page of memory map to the wireless units. The first thing that is to be received is the
location to be stored. Once this is set, each character received will be written directly to the LCD
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