GPS

1. GPS ­- When people talk about "a GPS," they usually mean a GPS receiver. The Global Positioning System (GPS) is actually a constellation of 27 Earth-orbiting satellites (24 in operation and three extras in case one fails). -- The U.S. military developed and implemented this satellite network as a military navigation system, but soon opened it up to everybody else. -- Each of these 3,000- to 4,000-pound solar-powered satellites circles the globe at about 12,000 miles (19,300 km), making two complete rotations every day. The orbits are arranged so that at any time, anywhere on Earth, there are at least four satellites "visible" in the sky.

2. GPS Working -- A GPS receiver's job is to locate four or more of these satellites, figure out the distance to each, and use this information to deduce its own location. -- This operation is based on a simple mathematical principle called trilateration. -- Trilateration in three-dimensional space can be a little tricky, so we'll start with an explanation of simple two-dimensional trilateration.

3. 2-D Trilateration Imagine you are somewhere in the United States and you are TOTALLY lost -- for whatever reason, you have absolutely no clue where you are. You find a friendly local and ask, "Where am I?" He says, "You are 625 miles from Boise, Idaho." This is a nice, hard fact, but it is not particularly useful by itself. You could be anywhere on a circle around Boise that has a radius of 625 miles, like this: You ask somebody else where you are, and she says, "You are 690 miles from Minneapolis, Minnesota." Now you're getting somewhere. If you combine this information with the Boise information, you have two circles that intersect. You now know that you must be at one of these two intersection points, if you are 625 miles from Boise and 690 miles from Minneapolis. If a third person tells you that you are 615 miles from Tucson, Arizona, you can eliminate one of the possibilities, because the third circle will only intersect with one of these points. You now know exactly where you are -- Denver, Colorado.

4. 3-D Trilateration Fundamentally, three-dimensional trilateration isn't much different from two-dimensional trilateration, but it's a little trickier to visualize. Imagine the radii from the previous examples going off in all directions. So instead of a series of circles, you get a series of spheres. In order to make this simple calculation, then, the GPS receiver has to know two things: • The location of at least three satellites above you • The distance between you and each of those satellites

5. GPS Solutions

6. TC6000GN • GPS module NMEA output • GPS all-in-one module • GPS tracking sensitivity -162dBm • Very small package • One single power supply • Low power consumption • Integrated LNA and TCXO

7. TC6000GN • TC6000GN-P1 is a high performance fully autonomous GPS module that outputs NMEA on a serial port and minimizes the load on the host processor. Protocol communication is NMEA (provides time, position, speed, satellite status, and course) • Adding an antenna, a 32,768Hz clock and a single 1.8V power supply will form a complete antenna–to- NMEA high performance GPS solution. • TC6000GN-P1 is a fully autonomous GPS module that outputs NMEA on a serial port with minimal requirement from a host processor. • Depending on the application, different configurations and additional components must be added.

9. Reference circuit • The circuit shows an implementation with a level shifter that allows to connect TC6000GN-P1 to 3.3V system. The 3.3V to 1.8V regulator (LDO or switch mode) is not shown. • A LED driver is shown to indicate the current fix mode by a LED • The PUSH_TO_FIX pin is available on the input of the level shifter to allow an external controller to put the TC6000GN-P1 to deep sleep. • For the antenna, two different options are shown. A passive antenna with matching and a connector for an active antenna alternatively. The active antenna configuration includes the decoupled antenna supply voltage. The coil blocks the RF path to the supply, the capacitor blocks the DC path towards the GPS_RF input • The GPS reset is shown with three options: reset through R/C circuit, through microcontroller or through a special reset chip, that generates the reset pulse. • The 32,768Hz clock can be provided by a dedicated oscillator circuit or by feeding an external clock  

11. UART -- UART module in the MSP430 to enable communications with a computer. -- The Universal Asynchronous Receiver/Transmitter (UART) module is part of both the Universal Serial Communication Interface (USCI) Module and the universal synchronous/asynchronous receive/transmit(USART) Module. -- Depending on which derivative of the MSP430 you are using, you will use either USCI or USART and enable one of the modes of operation such as UART, SPI, I2C, etc.

12. Hardware Connection -- UART is simple to connect and it uses 2 lines: TX (Transmit) and RX (Receive). No clock is required because it’s asynchronous. -- When interfaced to another module that uses UART, you will need to cross connect the lines. The TX of one device will connect to the RX of another device, while the RX will be connected to the TX of the second device. -- RS232 is a common connection between PC and devices, and it can be easily converted to RS232 using a level converter. -- Another popular solution is to connect the UART of the MSP430 to a USB to UART converter such as the FT232RL and FT2232 from FTDICHIP. These Ics creates a virtual COM port on the host machine that allows you to seamlessly transfer bytes between the host machine and the MSP430.

13. UART connectivity on the MSP430F5435