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Step3: GSM Modem Interfacing with 8051 Microcontroller GSM modem works with 12V DC and the microcontroller works with 5V. So, interfacing of this modem with microcontroller directly is not possible due to mismatch of voltage levels. GSM modem is interfaced with 8051 microcontroller through MAX232 with the help of RS232 cable for serial communication

Step2: GSM Modem Testing The GSM modem comprises of two light emitting diodes like green and red LEDs, which are used for the network connection indication. If there is no network is available, then the red LED glows, and if a network is available, then the green LED glows so that one can observe the working of GSM modem. Connect a power supply to a GSM modem which contains a SIM card and wait till it registers in the GSM network. For the testing of the modem, you can send an SMS to the modem. If it receives the message from the mobile, it is working properly, or else it is damaged.

Steps to Interfacing a GSM Modem to the Microcontroller Step1: Arranging the GSM Modem The GSM modem is a one type of modem, which uses the SIM card for communication. First, insert a SIM card into the modem which uses the same number/ account as the caller phone. It supports AT commands for handling the messages. These commands are programmed into the microcontroller ensures ending or receiving of the SMS from the modem.

A GSM Module is basically a GSM Modem  (like SIM 900) connected to a PCB with different types of output taken from the board – say TTL Output (for Arduino, 8051 and other microcontrollers) and RS232 Output to interface directly with a PC (personal computer). The board will also have pins or provisions to attach mic and speaker, to take out +5V or other values of power and ground connections.

GSM Modem A GSM modem is a device which can be either a mobile phone or a modem device which can be used to make a computer or any other processor communicate over a network. A GSM modem requires a SIM card to be operated and operates over a network range subscribed by the network operator.  It can be connected to a computer through serial, USB or Bluetooth connection. The GSM modem has wide range of applications in transaction terminals, supply chain management, security applications, weather stations and GPRS mode remote data logging.

20) What is Top half & bottom half of a kernel? Sometimes to handle an interrupt, a substantial amount of work has to be done. But it conflicts with the speed need for an interrupt handler. To handle this situation, Linux splits the handler into two parts – Top half and Bottom half. The top half is the routine that actually responds to the interrupt. The bottom half on the other hand is a routine that is scheduled by the upper half to be executed later at a safer time. All interrupts are enabled during execution of the bottom half. The top half saves the device data into the specific buffer, schedules bottom half and exits. The bottom half does the rest. This way the top half can service a new interrupt while the bottom half is working on the previous.

de and P-code. This modulated wave is called radio wave. Now the distance is equal to the time taken for the radio wave to travel from the satellite to the GPS receiver multiplied by the speed of the radio wave. Distance = Speed of Radio wave X Travelling time of the radio wave

How does GPS work? The crystal oscillator used in a satellite is the most important element in determining the almanac data. The accuracy of a crystal oscillator is measured in terms of PPM (Parts per Million). Generally, the ppm used in the satellite is in the order of 1ppm. This ppm varies with the temperature and responsible for shifting of frequency. Hence it is necessary to design and use accurate crystal. The GPS satellite generates two carrier frequencies (L1 and L2) located in L-band. L1 carrier is transmitted at a frequency of 1575.42 MHz and L2 carrier wave at 1227.60 MHz’. These carrier waves are modulated with C/A co

Space Segment consists of Satellites rotating around the earth and passing information (latitude, longitude, and altitude) to the GPS receivers. Moreover, it determines the UTC (Universal Coordinated Time). Control Segment This unit supervises the status of satellite and sends back the error and rectification data. The data is corrected and send back to the satellite. User Segment comprises the GPS receivers that collect the satellite information.

The GPS satellites in the space are designed in such a way that receivers capture the information 4 satellites at any time. It gets the calculated distance from the satellite. In order to receive the GPS signals, the sky has to be unclouded. Satellites transmit at two frequencies, 1.57542 GHz, and 1.2276 GHz. GPS also known as Global Navigation Satellite System (GNSS) is not a single subsystem and it is divided into 3 main components. They are Space Segment, Control Segment, and User Segment.

What is GPS? GPS is a tiny device used as a navigation receiver in ships, and aviator, smartphones and many more. It offers the position, navigation, and timing details in the space. GPS is the abbreviated form of Global Positioning System introduced by the Department of Defense (United States) for the military crew. This satellite navigation system is named NAVSTAR (Navigational Satellite Timing and Ranging).

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