Transcript sangeethadharini_gps_05282013x

- When people talk about "a GPS," they usually mean a GPS receiver. The
Global Positioning System (GPS) is actually a constellation of 27 Earthorbiting 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.
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.
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.
3-D Trilateration
Fundamentally, three-dimensional trilateration isn't much different from twodimensional 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
GPS Solutions
TC6000GN
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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
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.
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
-- 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.
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.
UART connectivity on the MSP430F5435