Ali Asgher Mansoor Habiby and Abdus Sami Abdul Qayyum, Sir Syed University, Karachi, Pakistan
EDN
When you go hiking or mountain biking, or simply take a long walk around the neighborhood, you might wonder about the distance you covered or specific details, such as speed. A specialized device for such a task is an expensive idea. Now, however, the increasing penetration of smartphones in the market with built-in GPS devices makes it possible to configure a mobile phone to log or send the current readings from its sensors to a server for viewing and processing.
This Design Idea describes a simple approach to log readings from a GPS using the Python scripting language. An advantage of Python is that an electronics engineer need not delve into the complex realm of C/C++ calls for Symbian/Android architectures to accomplish this simple task. All that is required is the installation on a phone of the Python interpreter, along with a text file containing the script.
The Python script initializes the mobile phone’s GPS and records location and speed data periodically in a file. It can upload the information via GPRS (general packet radio service) or send it using SMS (short messaging service) to another mobile phone. A .NET application that runs on any PC with a mobile phone connected receives the SMS to track a user in real time on maps provided by Google Maps. In cases where the expense of a PC and receiving mobile would be extra, it’s possible to import the tab-separated log file from the smartphone for manual data calculations.
The novelty of this idea, however, is in the use of a built-in accelerometer to calculate the number of steps taken when a user is walking or jogging and, based on this data, to calculate the amount of calories burned using one of many sample equations available (references 1 and 2). Hence, a total working pedometer and tracking system can be made using simple software in your smartphone without any additional hardware.
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| Figure 1. | The trackee’s location is displayed just after he or she turns on the mobile application. |
Figures 1 and 2 show two snapshots of the .NET application on the receiving PC. The app simply receives an SMS (with predefined format), parses it, displays the location/data on the map, and logs the information into a CSV file.
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| Figure 2. | The user sets the COM port connection to the mobile device. |
A few lines of code, available for download here, enable the device to use its GPS for receiving its current location. A single line then sends the location data via SMS to the destination number. The destination can be connected to a PC for logging and is playing real-time data. The code writes all information to a file on the mobile phone itself, in case the SMS option is not required and all data needs to be on the device for later analysis. A flow chart shows the functions of the code listings (Figure 3).
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| Figure 3. | The code listings write and send the data and initialize the GPS. |
Several components of the final design can be considered optional, as some users may want only the tracking app, and others might be content with a local file, without sending an SMS.
References
- Scarlett, Jim, «Application NoteAN-900: Enhancing the performance of pedometers using a single accelerometer,» Analog Devices, 2007.
- «Pedometer Steps to Walking Calories and Distance Calculator,» About.com.
Downloads
