Complete Specifications
Title of the Invention: GPS Based LED Destination Display Board Powered By
Single Microcontroller
Field of Invention: Embedded Electronics
Object of the invention:
The object of the invention is to provide a GPS based LED destination display board powered by a single microcontroller, in which the same microcontroller acts as GPS NMEA Decoder, Audio Processor, SD card reader/writer, EPROM I2C driver, LED scrolling Matrix Array driver, and external lights controller. This makes the device cost effective, smaller, and reduces power consumption which is very critical in vehicles such as buses.
Background of the invention:
In normal destination display boards used for buses, a separate GPS control board is required, and a separate LED display board is used to display the information sent in by the so said control box. Also a different control box is used for audio play. All these separate units raise the price of the whole device; moreover the power consumption is more.
In this invention, only one microcontroller is used which acts as a GPS NMEA Decoder, Audio Processor. SD card reader/writer, EPROM I2C driver, LED scrolling Matrix Array driver, and external lights controller. This reduces the power consumption, size, and cost of the whole unit. No separate control unit is needed, and a single microcontroller provides all functionalities.
Summary of the Invention:
The invention provides for a standalone GPS based LED destination board powered by a single microcontroller. The invention uses only a single microcontroller which acts as GPS NMEA Decoder, Audio Processor. SD card reader/writer, EPROM I2C driver, LED scrolling Matrix Array driver, and external lights controller. The same microcontroller drives the LED display, and also controls, drives and displays the data pertaining to destinations, both in visual and audio formats.
Brief description of accompanying drawings:
1. Sheet 1 of I shows different embedded program modules in a single microcontroller.
Detailed description:
A construction of a GPS based LED destination display board, powered by a single microcontroller is being presented here. The whole system is devised with only a single microcontroller. All the operations including NMEA decoder, SD card reader. Audio Processor, EEPROM controller and driver for driving 8 rows and 90 columns of LED matrix, are contained in this single microcontroller.
The use of only one microcontroller simplifies the design to make a destination board for indicating visually as well as audibly the next approaching station and other information such as time, date, advertisements, etc.
The whole microcontroller can be divided into following functional blocks:
GPS NMEA decoder Audio Processor SD Card Reader/Writer EEPROM I2C driver LED Matrix Array Driver External Lights Controller
GPS NMEA Decoder:
This functional block is the decoder for NMEA signals. The NMEA signals are detected, and only if valid fix is present in the NMEA signals, the NMEA codes are processed to make the calculations based upon the NMEA codes, i.e. finding the next approaching station, speed of vehicle, approximate time to reach all the upcoming stations/stops, real time and date, etc. The GPS is connected to the microcontroller via a software serial port operating at 4800 baud. The NMEA codes are received at 1200/4800 baud rate by NMEA decoder of microcontroller which is selectable to operate at 1200 or 4800 baud.
SD Card Reader/Writer:
This functional block of the microcontroller contains the routines to read and write the binary data to SD card. SD card of 128mb/512MB/ 1GB is supported by this microcontroller block. A software based SPi interface has been made for accessing the SD card. The SD card is used here because of its easy operation. The SD card can be removed from the socket attached to the microcontroller and can be taken away to upload the required data form computer. This makes the device more flexible. We don't have to connect the device to the computer to transfer the data. The SD card stores the latitude/longitude and names of all the stations/stops, advertisement, audio file for audio announcements, etc. Moreover, the SD card writer section is used to store the real time
information from the vehicle like time, speed, latitude and longitude that vehicle covered in a span of time. This information is then transferred to the computer for further assessment.
Audio Processor:
The audio processor is comprised of audio decoding routines that play the audio from the raw audio files read from the SD card via SD card reader block. The digital to analog converter is made by using 8bit port of microcontroller. The prior art of generating analog signals from digital values using PWM method has been dispensed away because of need of more processor power. So a simple and power full 8bit digital to analog converter has been made. The audio files pertaining to station/stop and advertisement announcements are stored in the RAW format in SD card. These files are loaded from the SD card and are played into the amplified speakers via this audio processor.
EEPROM I2C Driver:
This block contains the I2C routines to access the external EEPROM. The external EEPROM is used to store the font pattern information for LED Matrix display block. Other information like device ID is also stored in this EEPROM. Routines to access the (read/write) the EEPROM is contained in this block. SDA and SLC signals are generated in this microcontroller. External pull-ups on these lines are required and are made up of 1 OK resistors.
LED Matrix Display Driver:
A scrolling LED matrix board of about 8 x 90 pixels is made in this microcontroller which is very good and large enough to display the information like: next station/stop name, temperature, time, date, advertisement, distance to all following stations/stops, speed, etc. This block comprises of Row and Column drivers that can be connected to LED matrix to make a scrolling message board.
Row Driver for LED Matrix Array:
A software block has been made to facilitate the driving of 8 rows of a LED Matrix array. This drive is used to make a scanned LED matrix that is used to show different messages visually. This driver can drive any type of LED's via appropriate power drivers. Only few transistors are needed for more power output to drive high power LED's.
Column Driver for LED Matrix Array:
A complete Scanned LED display driver is made in this controller. The column section is made up of column driver that drives about 90 columns of LED matrix. The columns are scanned at about 70hz for greater brightness of LED's and less flicker rate. The column drive is serial signals that are adequate to drive the low cost serial to parallel converters that in turn drive the columns of LED matrix.
External Lights controller:
An output from the microcontroller is made available that outputs high level when the vehicle is approaching the station/stop. The level goes low when the vehicle leaves the station/stop. This helps in automation of the interior lighting of vehicle. This signal can also be used to illuminate the front and rear static destination boards installed outside the bus/vehicle.
One Second Pulse Output:
Precise GPS based one second pulse output is also made available from this microcontroller for use in specific situations/circuits.
Crystal Oscillator:
20Mhz crystal is used to clock the microcontroller.
Basic Functions of the GPS based led destination display board powered by a single microcontroller:
1. Display of next station/stop.
2. Display of advertisements, and general announcements.
3. Display of approximate time of reach of all coming stations.
4. Display of date and time.
5. Audio announcements of next stations and stops.
6. Automatic indoor lights on/off during/after destinations.
7. Automatic illuminations of static front-rear destination boards

I claim:
1. A method, the associated apparatus of GPS based LED destination display board powered by single microcontroller, where the said single microcontroller acts as a GPS NMEA Decoder, Audio Processor, SD card reader/writer, EPROM 12C reader/writer, LED scrolling Matrix Array driver, and external lights controller, in such a way that it is able to pick NMEA codes from the GPS and covert them to display destinations over a LED screen, such that the destinations will include current bus stop, next bus stop, the expected time of arrival, and other social and commercial advertisements, in both audio and visual formats.
2. The apparatus of claim 1 wherein a microcontroller is used.
3. The apparatus of claim 2 wherein the firmware inside the microcontroller makes the microcontroller act as a GPS NMEA Decoder. Audio Processor, SD card reader/writer, EPROPM 12C reader/writer, LED Scrolling Matrix Driver, and External lights controller.