GSM localizer without GPS Schematic

  
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The circuit our localizer is based on consists only of a quad-band GSM/GPRS module interfaced with a a microchip microcontroller which, after initializing the I/Os and UARTs it has at its disposal, puts the main program in a loop waiting for some event, which could be the arrival of an SMS or someone pressing the button P1 (that is, the logical 1/
GSM localizer without GPS Schematic - schematic

0 transition of the RB1 line, internally equipped with a pull-up resistor). In the event that an SMS is received, the localizer distinguishes between a message that is setting up a configuration and one that is requesting information regarding the position. Let us look more closely at the procedure that allows to find out the position, which is essentially the same in the case of manual requests as well as when pressing P1 (alarm or SOS): as soon as a request is received, the PIC orders the cellular module to connect to the Google Maps server in data mode (via GPRS, hence on the Internet) and to send a position request along with the cell ID to which Enfora is connected; now the localizer is ready to receive Internet-transmitted data on the RX channel of its own UART. Once the localizer receives the data with conjectured position (latitude and longitude, approximate street or square location) and accuracy, it prepares an SMS and sends it to the number that requested it or to the one that is stored and associated with this particular alarm function. That is all: simple and functional. The cell phone is handled by the microcontroller by means of the RF1 line (through which it reads the RI, that is, the Ring Indicator used by the module to signal the arrival of a call), as well as RB4 line, which allows it to detect receipt of SMS messages. RC7/RX1 and RC6/TX1 are, respectively, the reception and transmission lines of the...



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