Clocks that are synchronized with the Global Positioning System (GPS) show the correct time. These clocks are used everywhere, like at airports, bus stops, and train stations. These are also used a lot in the military.

Here, we talk about a GPS clock made with an Arduino Uno R3, which is a microcontroller board based on the AVR ATmega328 chip and has six analog input pins and 14 digital input/output (I/O) pins. It has 32kB of ISP flash memory, 2kB of RAM, and 1kB of EEPROM. The board lets you talk in a serial way using UART, SPI, and I2C.

Circuit and how it works Fig. 1: Block diagram of GPS clock using Arduino Figures 1 and 2 show, respectively, the block diagram and circuit of the GPS clock made with Arduino. In addition to the Arduino Uno board (BOARD1), the circuit uses a SIM28M GPS receiver module (GPS1), a GPS antenna (ANT.1), a 9V DC power supply adaptor, and a few jumpers for header connections. Here, we tried to get GPS time and date from a string ($GPRMC) that comes from GPS. About 70 characters make up this string. Figure 2 shows

that Arduino is in charge of everything and receives GPS output signals. When Arduino gets the GPS output, it reads all of the strings and puts the ones it needs in a string or an array in the Arduino program. After storing the required string, Arduino pulls the time and date from the stored string and sends it to LCD1 so that the time and date can be shown. The data pins D4 through D7 of LCD1 are connected directly to Arduino pins 5, 4, 3, and 2. The EN and RS control pins of LCD1 are connected to Arduino pins 11 and 12, respectively. The Tx pin of the GPS receiver is directly hooked up to the Rx pin of the Arduino board. Keep in mind that the ground pins on both Arduino and GPS should be connected. Here, a 9600bps baud rate is used to run the GPS module. In the Arduino sketch, the class Serial.begin(9600) function is used to set the baud rate to 9600bps.

Fig. 2: Circuit diagram of GPS clock using Arduino How GPS works As shown in Fig. 3, the GPS receiver's output can be seen on the Arduino's serial monitor. Use the same connections as above to get this GPS data, but take the microcontroller ATmega328 off the Arduino board. Then, open the Arduino IDE and choose the Serial Monitor option to see the format of the GPS output. This window has a lot of strings, but you only need to use $GPRMC. Here, you can see the date after the ninth comma and the time in 24-hour format after the first comma. Date and time are taken from this $GPRMC string by an Arduino program, which then processes them and shows them on LCD1. Software The software program that is loaded into the memory of Arduino Uno controls how the circuit works. Arduino is the language used to write the program (gpsindia.ino). The program is put together and sent to the board using Arduino IDE 1.6.4. Connect Arduino board to PC and use Arduino IDE to choose the right COM port. Make the program or sketch work. In Arduino IDE, choose the right board from the ToolsBoard menu and then upload the sketch. Programming doesn't need any outside header files for this project.