Palm Programming: GPS receiver

This paper looks at the process of developing an application for a device running a Palm operating system; specifically, any device running OS 3.x or newer. The main focus is broken into two separate ideas: understanding the process flow and minimum requirements of any Palm application and the development of a program to receive and display data gathered from a Garmin GPS 25 LVC receiver unit. All of the programs, processes, and ideas contained herein are based on the use of CodeWarrior, a developer’s environment for the PC available as freeware from Metrowerks Corporation.

As with any programming environment, the programmer must first learn the basics of how the computer functions. Most programmers are familiar with the PC environment and standard flow of an application. When programming in any language on a PC, the developer must create and include any functions or additional files that are necessary for use with the application being created. However, the Palm OS is slightly different, and rightfully so considering the limited storage capacity available on most handhelds. When a Palm application is being developed, many of the functions that are going to be needed for performing the most comm

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The fourth file is another header file which is not automatically generated but must contain the function prototypes for any function in the main source file. By providing these functions to the developer, it helps to not only ensure compatibility with all of Palm’s devices, but also speeds the development process. Application handle events are events set up by the programmer to happen when the user performs a specific action such as a button press or writing specific characters.

The next major portion of PilotMain is the EventLoop or sometimes called the AppEventLoop. The program does gather data and display it properly but the device must be run through a soft reset when exiting the application by pressing the on screen reset button.

The first step in developing the program was to decide how the user interface would appear and what special objects were necessary. In the folder, two files are created called starter; one is a resource file for constructor and the other is the source file with the standard stationary code. Under the assumption that there was likely a programming error the code was modified and rearranged into several different configurations to attempt to remedy the problem.

The third object is a resource header file. The GPS program requires that the serial port be continually searched for new data on some specific increment of time. This main form acts as the backdrop for all of the actions that will occur in the program. The function is designed to read the data, separate it into usable strings, display the appropriate information, and do any necessary error checking. The entire source code is contained in Appendix C. There is a particular flag in the data that lets us know whether there were enough satellites in view to triangulate the position of our receiver. For most programs, the compiler looks at this function when the program is executed.

Approximate Word count = 2997
Approximate Pages = 12 (250 words per page double spaced)

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