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Step 3: GEO-TAGGING DATA: THE LS20031 GPS RECEIVER

LS20031 GPS RECEIVER SPECIFICATIONS

I am using the LS20031 GPS receiver in this prototype to tag logged data with both geographic location and date/time stamp. The LS20031 is a bread and butter GPS receiver. It's very simple to operate. This receiver is made by LOCOSYS Technology. I have attached the LS20031 datasheet to this section for those interested in more detailed specifications. 
  • Model: LS20031
  • Chip: MediaTek MT3329
  • Voltage: 3.3V
  • Frequency: L1 1575.42MHz, C/A code
  • Channels: Support 66 channels (22 Tracking, 66 Acquisition)
  • Update rate: 1Hz default, up to 10Hz
  • Hot start: (Open Sky) < 2 seconds (typical)
  • Acquisition Time: Cold Start (Open Sky) 35 second  (typical)
  • Autonomous 3m (2D RMS)
  • Position Accuracy: SBAS 2.5m (depends on accuracy of correction data)
  • Datum: WGS-84 (default)
  • Max. Operating Altitude: < 18 Km
  • Max. Operating Velocity: < 515 m/s
GPS RECEIVERS & NMEA SENTENCES

When the GPS receiver is powered up, it will start transmitting information via it serial (TX) pin in the form of standardized comma-delimited text lines. These standardized text messages are called NMEA sentences containing latitude, longitude, date/time, among other useful data. 

NMEA stands for National Marine Electronics Association. This is the industry body that comes up with standardized message formats for GPS receivers to simplify using this technology. 

NMEA sentences start with GP + a three-letter identifier that tells us what sort of data is contained in this NMEA sentence being transmitted by the GPS receiver.

The LS20031 sends out the following NMEA sentences.
  • GGA Global positioning system fixed data
  • GLL Geographic position - latitude/longitude
  • GSA GNSS DOP and active satellites
  • GSV GNSS satellites in view
  • RMC Recommended minimum specific GNSS data
  • VTG Course over ground and ground speed
The one I find useful for this project is the RMC ($GPRMC). Here's a sample RMC sentence and an explanation of each element:

$GPRMC,053740.000,A,2503.6319,N,12136.0099,E,2.69,79.65,100106,,,A*53
  • Message ID: $GPRMC RMC protocol header
  • UTC Time: 053740.000 hhmmss.sss
  • Status A: A=data valid or V=data not valid
  • Latitude: 2503.6319 ddmm.mmmm
  • N/S: Indicator N N=north or S=south
  • Longitude: 12136.0099 dddmm.mmmm
  • E/W Indicator: E E=east or W=west
  • Speed over ground: 2.69 knots True
  • Course over ground: 79.65 degrees
  • Date: 100106 ddmmyy
  • Magnetic variation: degrees
  • Variation sense: E=east or W=west (Not shown)
  • Mode A: A=autonomous, D=DGPS, E=DR
  • Checksum: *53
  • End of message termination

POWERING AND WIRING THE LS20031

I mentioned earlier that I had published a guide to help configure the LS20031 GPS receiver. The LS20031 is a 3.3V module which means it's powered by a 3.3V source. This also means we cannot connect the Arduino output pins, such as the TX pin (5V), to the LS20031 RX pin (3.3V) without converting from 5V to 3.3V.

In this prototype, I use the SN74AHC125 as level-shifter from 5V to 3.3V. We should be able to take the LS20031 GPS serial output pin, the TX pin (3.3V), and wire it directly to the Arduino's serial RX receive PIN1 (5V). The Arduino's 5V pins can handle a 3.3V signal and will treat it as a logical high.

CONFIGURING THE LS20031

For this prototype I used MiniGPS 1.4 to configure the LS20031 GPS receiver as follow:
  • Baud rate: 4800
  • Fix Update Rate: 5/sec
  • NMEA outputs: RMC output set to 1 while all other NMEA outputs set to zero (0). At 5Hz, this means 5 RMC messages per second. 
I know this may sound confusing to some of you but please stick to my settings. Once you get your prototype up and running you can change the parameters. 
<p>Can anyone help please? I am new <br>to this, and been trying to put together the project. So far I have everything <br>assembled as instructed. However, as soon as I try to verify the code, I get <br>this error:</p><p>Arduino: 1.6.5 (Windows 7), Board: &quot;Arduino/Genuino <br>Uno&quot;</p><p>C:\Program Files <br>(x86)\Arduino\libraries\SD\src\utility\Sd2Card.cpp:26:17: fatal error: SPI.h: <br>No such file or directory</p><p>#include <br>&lt;SPI.h&gt;</p><p>^</p><p>compilation terminated.</p><p>Error compiling.</p><p>What do I need to do to fix this?</p>
<p>Newer versions of Arduino IDE can't find the SPI library, so you need to add them by adding the following line at the start of sketch:<br>#include &lt;SPI.h&gt;<br></p>
<p>I'm no expert but had this same problem on another project. All of the files (including the additional libraries) need to be in the right folder. The Arduino IDE seems to be a bit picky about this (on Linux at least).</p>
<p>can i have the code for storing Accelerometer ADXL335 data into SD card with time staps (say every 5 min interbal)</p><p>and how can name the stored file as a YYYYMMDDHHSS format </p>
<p>could not get code to compile</p>
<p>I made an equivalent tool in python that print real time data from ADXL345 accelerometer.</p>
<p>like</p>
<p>I made an equivalent tool in python that print real time data from ADXL345 accelerometer.</p><p><a href="https://github.com/mba7/SerialPort-RealTime-Data-Plotter" rel="nofollow">https://github.com/mba7/SerialPort-RealTime-Data-P...</a></p><p>may be it will be helpful for someone</p>
<p>I made an equivalent tool in python that print real time data from ADXL345 accelerometer.</p><p><a href="https://github.com/mba7/SerialPort-RealTime-Data-Plotter" rel="nofollow">https://github.com/mba7/SerialPort-RealTime-Data-P...</a></p><p>may be it will be helpful for someone</p>
<p>I need create a file GPS.log in SD card before do this work ? Or the file GPS.log will be created by code?</p>
<p>You can read the accelerometer more often than the GPS, so there should be no need to interpolate the accelerometer reading.</p>
<p>great</p>
<p>good</p>
<p>super</p>
<p>super</p>
<p>In this tutorial I find what I need to start interfacing the gps sensor with an Arduino. And because I want to help many more hobbyists to start building robots, I share this tutorial on my post http://www.intorobotics.com/gps-sensors-tutorials-resources/. Thank you!</p>
<p>Hello techbitar - I'm thinking of building an adaption of your project but am considering changing the SD card adapter to the microSD card shield from Sparkfun: https://www.sparkfun.com/products/9802</p>
True but not all sensors (temperature, humid, etc.) possibly used by others will be as fast as the accelerometer I am using in my project.
Hello techbitar, <br> <br>I just ordered all the hardware for this project, and I should be beginning it some time next week. I just had a question. Obviously all of these components would need to be powered up whilst in car data collecting while driving, so would one of these do the job: http://www.radioshack.com/product/index.jsp?productId=3802146 . Also, I got this for the 'in-home' programming and construction of the actual project: https://www.sparkfun.com/products/9442? ..... Do you think that'll be good as well? I would assume so.
The Arduino Uno specs are as follows: <br>Input Voltage (recommended) 7-12V <br>Input Voltage (limits) 6-20V <br> <br>As for current, I have tested my Bump-O-Meter with a USB connection which provides 5V and up to 0.5A. I did not run into any issues but I did not perform any exhaustive tests. <br> <br>While driving around in my car, I powered the Arduino Uno via the DC plug using a battery brick made of 6 X 1.2V (NiMh) = 7.2V @ 2A. That voltage is close to the minimum recommended voltage. It worked but of course the moment the battery dropped to 6V and below I am sure I would have ran into all sorts of issues. <br> <br>If I go production with this, I would use a 3S LiPo for a cool 11.1 Volts and 1.5A or 2A current for safety margin in case I need to add additional power hungry gizmos to the bump-o-meter. <br> <br>Check you choices of power supplies against the min/max voltage specs and add a comfortable margin to the current with an eye on your future plans. then decide what fits your requirements best.
I was riding my bike recently and remarked to another rider that it would be useful to quantify just how bad our roads are. My thinking is to first breadboard components as you have laid them out, and then substitute an Arduino Micro and micro SD card reader for compactness. While I like LiOn batteries, a 3S 11.1V 2 amp battery is fairly large (and heavy and needs a requisite charger). Do you have an idea for a compact battery with a 3-hour runtime?
Hello techbitar - I'm thinking of building an adaption of your project but am considering changing the SD card adapter to the microSD card shield from Sparkfun: https://www.sparkfun.com/products/9802 <br> <br>Do you see any obvious problems with this change, and would it break the code you've written? Cheers
I have not tried it but if it Sparkfun's SD adapter does not work out of the box you may need to tweak my circuit and/or code.
You can read the accelerometer more often than the GPS, so there should be no need to interpolate the accelerometer reading.
True but not all sensors (temperature, humid, etc.) possibly used by others will be as fast as the accelerometer I am using in my project.
You're welcome.

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