How to Interface a GPS Modem with PIC Microcontroller

For the policemen, nabbing criminals has always remained a big challenge. However, the ever increasing technological advances like the usage of electronic devices with GPS system, to a certain extent, have eased their challenge. Thus, GPS system plays very crucial role for all types of security and communication systems used in railways and location based systems.

This article is intended for those enthusiasts who are really looking forward to use GPS system as a practical interface with microcontroller. After going through this article, one will be able to interface GPS with a GSM or PC

A Step-By-Step Procedure to Interface GPS Modem with a Microcontroller

Before starting this procedure, ensure that all accessories necessary to interface are at hand. Such accessories include GSM Modem, microcontroller and other such circuit accessories.

Step1: Match the Power Supply

In this step, the interface is with a PIC microcontroller rated at 5V or a low rating which may not match exactly with the GPS modem. Therefore, there is a need to design additional power supply unit – other than the microcontroller power supply unit. Such a designing process includes rectification, filtration and regulation of units to obtain a regulated DC supply from the mains AC supply.

Step2: Connect the Communication Terminals

In this step, connect the Rx and Tx pins of the GSM modem to the Tx and Rx pins of the microcontroller through a level shifter IC. A DB9 connector is used to connect this modem to the level shifter IC. While using GSM modem or PC interface to see the results (longitude and latitude), there arises a need to use multiplexer IC to interface with the microcontroller. Since the microcontroller has only one set of Rx and Tx pins, both GSM and GPS modem cannot be interfaced at a time.

In this set up, a MAX232 is used as a level shifter IC to convert the RS232 signals of GPS or GSM modem or PC to the TTL signals of the microcontroller. This level shifter IC is then connected between the multiplexer IC and the GSM/GPS modem.

Step3: Code for Acquiring Desired Data

This step in other words is known as valid data capturing. The microcontroller is so programmed that it takes only the data that corresponds to the longitude and latitude while leaving unrelated data like time, degrees, etc. And also considers the baud rate of the GPS modem to match with the communication.

If the project involves a GSM modem to send the location information to a remote mobile, then there is a need to program this microcontroller. And for the LCD display and the PC interface via the HyperTerminal software the microcontroller needs to be programmed.

These are some of the very essential steps to interface the GPS modem with the microcontroller. In addition to this, the following system is a practical project based on GPS system using a microcontroller.

Vehicle Theft Location Intimation to the Owner by a GPS/GSM

The main aim of this project is to find a vehicle theft location, and to send that information to the owner, or the concerned authorities through SMS. The system here uses a GPS modem to track the exact position or place in terms of longitude and latitude values, and a GSM modem to send SMS, in addition to a microcontroller and other circuit accessories, as shown in the figure.

On receiving the location information, the GPS modem transfers these signals to the microcontroller via a level shifter IC, i.e., MAX 232. This IC also interfaces GSM modem to the microcontroller. As we discussed above, a multiplexer is also connected between this IC and the microcontroller to select GPS or GM modems based on the operation.

The Microcontroller is programmed in such a way that depending on the signals from the GPS, it filters the information from the overall data to a required data and sends that information to a LCD. The LCD display, depicts the longitude and latitude direction on its display. A user can identify the exact location by placing these values in the maps application.

This longitude and latitude information is then transferred to the GSM modem that in turn sends this data to the mobile number that has been stored previously in the microcontroller such that the owner of the vehicle can find the information about the vehicle.

This is all about interfacing a GPS system to a microcontroller circuit with an example. We hope that you will find the information about interfacing procedure immensely helpful, and therefore, anticipate your comments, suggestions, feedback and doubts regarding this article in the comments section given below.