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Thread: GPS vehicle tracking, any advise ?

  1. #16
    Raw Wave
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    i will then enter the data manually into my gps software on my pc that will show me the current location

    Isnt possible to rip the text message from the phone via software with datacable...and then into the GPS software? Perhaps process it again as if its is like a $GRPMC sentence and then output it to a virtual com port? This should ensure better compatibilty. Problem is if this is used for live tracking then the tracking phone need to constantly text the phone...the tracking phone will run out of credit.


    A clever thief not many of them about, but if there was one who deceided he would be clever and locked u your car up in a garage no GPS signals

    The GPS should still be able to transmit the last known position...so you should be able to find if the car is locked in the garage...unless of course the car is put in a truck and moved somewhere else.

    i can use DTMF tones using a decoder circuit to control the system and to request functions via a simple dtmf tones hey theres 16 avliable and only 12 keys on a keypad so i may use a pic to accept a unique code for access and allow infinite outputs via dtmf say "23#"

    Why not use your phone to text the tracking phone to turn on/off a device? At least you dont have to carry a DTMF tone generator.

    Of course all this need to be controlled by a MCU.

  2. #17
    Constant Bitrate b_nom's Avatar
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    Quote Originally Posted by [iG]
    blackbox wont allow you to 'track' the car, all it does is replay the routes later.
    guess i didn't understand the question , maybe I should read the WHOLE post next time
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  3. #18
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    Heres a basic block diagram of my project and I hope its not too complicated for some.

    I have done the PIC program and its under test on PIC16F627 will be upgrading it to PIC16F648 for more memory.

    The idea is to use a normal phone (pay-as-you-go with no credit). Im using a nokia 3310 for my test. I wanted to stick to normal phone that most poeple should have laying around. It is still rare to find a spare phone with real hardware modem...most either dont have one or just use a software based modem.

    Anyway heres a quick rundown of my progress. The GPS 4800 baud NMEA sentences are fed to the controller, the controller ignore all the sentences apart from $GPRMC. This $GPRMC is then stored in the PIC internal buffer. This is then read internally and retransmitted through the FSK modulator at 300 baud. The FSK is generated by the PIC hardware PWM module, through a filter before being fed to the mobile mic input.

    The frequency of the FSK is 1200/2400Hz, which work fine when passed through the phone digital network. It is important to slow down the transmission rate from 4800 to 300 baud due to the way the voice is compressed and decoded in the mobile phone.

    On calling the tracking phone, the receiving phone should then output the 300 baud FSK signal. This can be from a landline phone directly outputing the signal to the controller via the phone audio out, the mobile phone audio out or through a phone pickup device.

    Another PIC is programmed to detect the 1200/2400Hz tone as a '1' or '0'. This is done throught DFT calculations to determine the presence of the 2 tones. The decoded output is then reshaped, decoded and stored in the buffer. The buffer is then read by the 4800 baud transmitter and out to the PC comport. The same $GPRMC sentence is always transmitted until a new one is available...the update happen once every 2 seconds.

    At this moment Im able to read the GPS NMEA and transmit the $GPRMC at 300 baud FSK. I have tested it from mobile to landline all seems to work fine. The FSK signal is received via a pickup device attached to a land line phone "BT diverse 4010" then into the PIC. The PIC can decode the signal very well which is then fed to the PC comport.

    I have got the hardware FSK decoder working...but however it is possible to write a windows software that can decode the FSK signal and then output it to a virtual comport. The FSK signal from the phone is fed into the line-in of the soundcard. The software then analyse the signal, looking for 1200/2400 tones and regenerate the '1's and '0's on the virtual comport. A program called TRUETTY can do just this.

    I dont have enough knowledge about programming such application. This software based decoder will elimate the hardware based decoder and therefore even cheaper solution can be made. About 5-10 add-on will turn your spare mobile phone into a tracking device.

    I think it should be fairly straight forward for an experienced programmer to program an all software FSK decoder...all thats needed are :

    1) The 300 baud FSK signal from the phone is read by the soundcard line-in or mic.
    2) The software then analyse this FSK signal and decodes the data in real time.
    3) The decoded data is then outputed to a virtual comport at 4800 baud.

    Well I hope someone can help me out with this one

    At the moment Im still putting all this together. Im soon hoping to control the mobile phone with the PIC via the data cable...this should allow me to text if the car need attentions.
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  4. #19
    Maximum Bitrate Danceheaven's Avatar
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    Ricky327,

    Yes i agree ripping the lon / lat data form the text message would be the best option and most compatible such as live update via gprs to a web page will equally be as good.
    as for credit you can request cordinates via the dtmf functions call up and manually request an update you could specify the update time or just a one off position.

    GPS last position i agree again this will allow for last position to be recieved and will disallow the need for another rf interface, as for moving the vehicle in a truck ofcourse this will be a problem..... lets hope there arnt many clever thiefs out there.

    If i was to use a text msg to turn on and off devices from my phone to the tracking phone i would need to make sure that syntax was correct for every text i sent plus making sure that text has arrived safely sometimes a big delay can take place, also i would need to purchase a RS232 gsm modem that allows for the sms data to be extracted via AT cmds, having it dtmf controlled will let any phone be used that supports dtmf most mobiles do and so do tone dialing type telephones.

    MCU controlled definatly.... i wouldnt risk the use of the car pc during this tracking it may fail or crash or just run out of power.... ofcourse a log of lon and lat could be written to a text file for later viewing if needed.

    As for cost like you say if you have an old mobile phone lying around that be perfect for the dtmf side of things as for actually trasnmitting hte NMEA data it would need to be capable of GPRS for web update or SMS compatible for text update or you could get the car pc to speak it to you for normal voice updates alough i would prefer option 1 or 2.
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  5. #20
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    making sure that text has arrived safely sometimes a big delay can take place

    Thats true.


    also i would need to purchase a RS232 gsm modem that allows for the sms data to be extracted via AT cmds, having it dtmf controlled will let any phone be used that supports dtmf most mobiles do and so do tone dialing type telephones.

    I thought you gonna use text to transmit the coordination? In that case you be needing a data cable anyway? so the PIC can control the tracking phone.

    I dont think a modem is needed just for texting and receiving text...Im almost sure sending and receiving info from the phone can be done just via datacable or infared.

    I may be wrong as I havent got as far as controlling the phone through the data cable. This is what I wanted to do soon...the PIC can answer the tracking phone, hang up the phone, send a text message to another phone and extract the text message from the phone. If you can confirm this is not possible without a modem then my plan would change. I should atleast be able to put the tracking phone on autoanswer so whenever I call it it will start to transmit the cordination by mean of FSK tones...well I cant see any autoanswer option on my test phone anyway


    As for cost like you say if you have an old mobile phone lying around that be perfect for the dtmf side of things as for actually trasnmitting hte NMEA data it would need to be capable of GPRS for web update or SMS compatible for text update

    Thats the whole thing why I decided to make my own 300 baud modem programmed into the PIC. The NMEA sentences is transmitted by tones of 1200Hz and 2400Hz through the mic input of a basic phone. I originally wanted to design a 4800 baud modem but then had to drop down to 300 baud due to the way the voice are being compressed when passed into a mobile phone. Since I couldnt get the 300 baud to work properly I gone even lower after reading alot of info on the net, some say its just not possible to transmit 300 baud through a mobile phone without a built in modem due to limited audio bandwidth and compression used. I know DTMF tone can pass through the phone without a problem. So in turn I made a DTMF modem, each DTMF tone is used to transmitt a nibble, a pair would make a byte. I abadoned the idea as I can only get 5 characters per second out of it, not exactly good for live tracking. Anyway after a few more hardwork I finally got the 300 baud modem working reliably...and Im gonna stick to it

    If you read my previous post, I know its long but I did explain how to even reduce the cost by using a software based decoder...may aim is to turn any old crappy phone into a cheap but effective tracking device

    Anyway thats my part.






    How far have you gone into your project?


    This is something you may wanna see :

    GSM-SMS tracker project

    Dont know if you seen it, but I think its similar to what you are planning to achieve.
    The idea didnt appeal much to me as it does say you must use a phone with a built in hardware modem...Im sure it did

  6. #21
    Maximum Bitrate Danceheaven's Avatar
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    Ricky327

    Sorry for the confusion because not everybody has the same phone lying around and if other people did want to use my tracker i was going to use a readily avliable GPRS modem with RS232 comms on it, just to keep things simple with software etc heres the one i was looking at at farnell.

    http://uk.farnell.com/jsp/catalog/vi...prodId=4317968
    but pricey though.

    Your perfectly right about the data cable part if i had a phone that supported a data cable and worked, (i broke mine ) i would use that or IR, or even bluetooth

    i like the way your using frequency shift keying for the data tx cool idea.
    the reason i was gonna use txt is so that i can manually request a position and if that fails there also the gprs web update option and if that fails then there is always the gsm tracking part. not very accurate but still if it can help locate your car then its great.

    you have by far got the most cost effective solution going on the forum for a tracker turning any old phone into a tracker, i did read the post you mentioned about the german tracker, i did a web translation on the page to get more info it looks ok but im adiment on designing my own,

    Project Progress is 0% still researching infact i havnt even purcahse my dev kit fot he MCU, may go for a microchip mplab ICD 2.
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  7. #22
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    Sorry for the confusion because not everybody has the same phone lying around and if other people did want to use my tracker i was going to use a readily avliable GPRS modem with RS232 comms on it, just to keep things simple with software etc heres the one i was looking at at farnell.

    Lol no problems...

    That GSM module look cool...it is expensive but still it is tempting though

    Project Progress is 0% still researching infact i havnt even purcahse my dev kit fot he MCU, may go for a microchip mplab ICD 2.

    Theres plenty of develepment kit for PICs. Im using the PICKIT and the Valleman PIC Programmer. It only cost 49 and 25 from maplins both are easy to use.

    Theres one member here who have experience in controlling the phone by MCU, texting and all sort...and willing to help out with the hardware and software questions. I think I got 1 or 2 to ask already

    Let us know how it goes.

  8. #23
    FLAC Spaghetti's Avatar
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    Sorry if this has already been mentioned (reading that lot above just made me dizzy... ), but if all the above is possible, in theory could you just text a password to your car and have it switch off automatically via a serial to relay/engine????? That would be veeeery cool indeed.....

  9. #24
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    Sure you can.

    Theres one member in here who used text to control appliances or something similiar. Look around, it is in another thread somewhere, theres also a link with all the details about it.

    The problem is I dont think texts are encrypted...It is possible for someone to hijack your text and will therefore know your password/code to turn you engine on/off.

  10. #25
    FLAC Spaghetti's Avatar
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    Yeah but.... that would mean that the usual average thieving scumbag would have to be one very *****ing clever bastard!!!! Even more clever than you guys...?? The likelyhood of him knowing that you're covertly tracking your car at all, never mind tracking him with your mobile(!), as well as getting past the alarm/immobiliser would be pretty slim!

    What would you do about keeping the computer switched on though...?

  11. #26
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    Yeah but.... that would mean that the usual average thieving scumbag would have to be one very *****ing clever bastard!!!!

    Hehe thats true, because it means he got to know what sort of security is being used at the first place.

    What would you do about keeping the computer switched on though...?

    Ermm...Ill go for a standalone unit.

  12. #27
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    have any of you guys seen this before? sounds very interesting.http://www.gps2000online.com/

  13. #28
    Maximum Bitrate Danceheaven's Avatar
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    The Design im doing will allow for two way communication using dtmf tones,
    passwords can be entered via tones followed by a hash to confirm any action, this way unlimited commands within reason will be able to control anything conneted to its outputs inside the car, its highly unlikely that a theif will be monitoring the tones while hes busy trying to nick the car and hide it somewhere i wouldve thought
    as for a third party person listening on the comms all he will here is tones
    plus the gsm protocol as i underdstand it has never been cracked in full i should say.
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  14. #29
    Maximum Bitrate Danceheaven's Avatar
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    I was thinking last night, (Careful i here you say), ricky if your using fsk to encode the nmea data and transmit it via gsm then decode it with a pic then feed this is to the com port on your local machine or tracking laptop if this comm port was set up as the comm for the gps reciever and you run say a mappoint or destinator wouldnt this show live tracking as in a exact duplication of the gps screen in the vehicle if it was running? or will the gps app need to initialsie the gps mouse first somehow?
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  15. #30
    Raw Wave Confused's Avatar
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    Quote Originally Posted by Danceheaven
    I was thinking last night, (Careful i here you say), ricky if your using fsk to encode the nmea data and transmit it via gsm then decode it with a pic then feed this is to the com port on your local machine or tracking laptop if this comm port was set up as the comm for the gps reciever and you run say a mappoint or destinator wouldnt this show live tracking as in a exact duplication of the gps screen in the vehicle if it was running? or will the gps app need to initialsie the gps mouse first somehow?
    Nope, the GPS software doesn't initialise the hardware, it just blindly reads (how it reads if it's blind I don't know, but it does for the purpose of this hilarious post ) the NMEA stream that's being sent to the serial port by the GPS.

    So yes, in theory, you should be able to see in (almost) real-time where the car is, it depends on how quickly you can send the stream through the phone


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