= DevelGPS v0.1 =

== Overview ==

The purpose of this project is to implement a portable GPS locator / geocaching
finder tool using the Cortex-M3 based Luminary Micro LM3S1968 evaluation board.

The device proposes a user interface to configure the GPS coordinates of a
target location and shows on the OLED display the direction and distance to
reach the target.

== Hardware requirements ==

 - Luminary Micro LM3S1968 Evaluation Kit
 - a GPS module
 - a mobile phone battery

== Software requirements ==

 - BeRTOS kernel

BeRTOS components used for this project:
 - Kernel with preemptive scheduler and task priorities
 - Device drivers: UART, OLED display, navigation/select pushbuttons
 - NMEA parser
 - GFX library (+ menu management module)

== Implementation ==

The GPS module is connected to UART1 RX pin (UART0 is kept for debugging
purposes). The mobile phone batter is used as a power source both for the GPS
module and the LM3S1968 board.

From the software's point of view, BeRTOS already provides the drivers to
manage all the required devices and a NMEA parser to retrieve the right
informations from the raw GPS strings: position, date & time, link quality.

The multi-process environment and preemptive scheduler provided by BeRTOS is
exploited to create independent threads operating in producer/consumer way:
 - a thread takes care of retrieving and processing NMEA string from the UART,
 - a thread manages the GUI, updating the OLED display on new GPS informations
   or user's input,
 - a thread reports the status of the GPS receiver blinking a LED when GPS data
   are correctly received.

The GUI is organized using a main menu that allows to select:
 - a form to insert the target GPS coordinates,
 - a form showing a compass with target direction, distance and GPS positions
   to reach the target,
 - a form to show the status of the GPS receiver.

NOTE: the distance is evaluated using the Haversine formula between the current
and target GPS position. The Haversine formula remains particularly
well-conditioned for numerical computation even at small distances, making the
device particularly useful when walking, hiking or moving at a close distance
to the target.