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GPS Tracker using SIM908

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The current firmware version available is 1137B04SIM908M64_ST

Cheers.
 

I am thinking of buying this module to make a low power tracking device, does anyone have a good PCB design to integrate with microcontroller?
 

Hi tkoWd,

I assume that you would do your own PCB and as for the micro, take your pick.

I use NUC1xx series from Nuvoton with SIM908.

Cheers.
 
Last edited:

Hi Batang,

I know a bit of electronics, however I have never designed PCB. I'm going to try Mentor Graphics PADS PCB. I will check the NUC1xx, but looking for low power micro because the system must last long periods of time in standby (and wake up upon triggered event).

Any recomendation in designing the PCB for SIM908? I am looking to connect some solar powered cell, so that the current used in standby is recovered.
Batang said:
Hi tkoWd,

I assume that you would do your own PCB and as for the micro, take your pick.

I use NUC1xx series from Novoton with SIM908.

Cheers.
Click to expand...
 

Hi!

My SIM908 GPS works now. I bought a better antenna for gps and I took a long coax-cable. Now I can program the microcontroller and the GPS works fine outside. I guess the old antenna broke down or something.
Now it works :)

The microcontroller I use is from Atmel. ATMega644V . For the communication between SIM908 and ATMega644V I prefer UART.
Also I am using a 1100mAh Li-Po battery and it works fine. Now I am programming the sleep mode, so all 15 minutes the module turns on and put the GPS coordinates on a FTP server. Also you can see on an Android App the current location on Google Maps.
The first prototype (self-made board) measures about 5,0 * 6,0 cm.
 

Serpent said:
Hi!

My SIM908 GPS works now. I bought a better antenna for gps and I took a long coax-cable. Now I can program the microcontroller and the GPS works fine outside. I guess the old antenna broke down or something.
Now it works :)

The microcontroller I use is from Atmel. ATMega644V . For the communication between SIM908 and ATMega644V I prefer UART.
Also I am using a 1100mAh Li-Po battery and it works fine. Now I am programming the sleep mode, so all 15 minutes the module turns on and put the GPS coordinates on a FTP server. Also you can see on an Android App the current location on Google Maps.
The first prototype (self-made board) measures about 5,0 * 6,0 cm.
Click to expand...

Hi Serpent,

Can you supply PCB design? Can the battery be larger than 1100 mAh?
 

tkoWD said:
Hi Serpent,

Can you supply PCB design? Can the battery be larger than 1100 mAh?
Click to expand...

Hi!
The design is not finished yet . the board will be design smaller ;) the programm I use is EAGLE from Cadsoft.

Yeah the battery can be larger than 1100 mAh . But dont charge with the sim908! it may break down . The 1100 mAh is just the capacity of the battery . if the capacity is larger the charging process will take more time. Advantage: The battery will supply the whole hardware longer
 

Serpent said:
Hi!
The design is not finished yet . the board will be design smaller ;) the programm I use is EAGLE from Cadsoft.

Yeah the battery can be larger than 1100 mAh . But dont charge with the sim908! it may break down . The 1100 mAh is just the capacity of the battery . if the capacity is larger the charging process will take more time. Advantage: The battery will supply the whole hardware longer
Click to expand...

Sorry I didn't understand the 'it may break down'. Can I use a 4400 mAh battery? or will it not charge?
 

tkoWD said:
Sorry I didn't understand the 'it may break down'. Can I use a 4400 mAh battery? or will it not charge?
Click to expand...

The internal charging circuit may damage your module. I damaged mine during the charge mode . but of course you can try it , maybe your module will still work ;)

Yeah of course you can use a 4400 mAh battery , but the charging process will take more time . I guess about 3-5 times longer .

I will design an external charging circuit for Li-Po batteries soon
 

Serpent said:
The internal charging circuit may damage your module. I damaged mine during the charge mode . but of course you can try it , maybe your module will still work ;)

Yeah of course you can use a 4400 mAh battery , but the charging process will take more time . I guess about 3-5 times longer .

I will design an external charging circuit for Li-Po batteries soon
Click to expand...

Thanks for the heads up. Is it possible to charge and use at the same time? I want to have a solar cell recharge the battery as much as possible when sun is available. Lithium Ion don't require full discharge cycle so I guess they are a good choice.
 

Dear Echo wang ,

I am too a newbie and I also have to complete my project using sim908. Would you like to share some materiel with me that would help me use the SIM908?
I would like some PDFs what would help a new beginer use the SIM908.

please kindly share some with me.
amalinda.gamage at gmail dot com

this is for my final year project and your help would be so much appreciated.



below is my problem if you wouldnt mind reading

----

I want to build a small sized, solar charged ,portable circuit that transmits the GPS location automatically to a server using GPRS/SMS.(webserver is capable of accepting sms)

this module is worn by a certain type of animals and their location would be thus be displayed on the tabs on the authorities that can access the data on the web server through internet. (WebServer tab connectivity already completed)

please share come meterial with me. thanks
 

Hi Friend,
sorry for asking i am new user but i am currently working on gps system by which interface these AT commands are sent i have microcontroler of stm stm32f103 but i dont know how to send these AT COMMANDS please if u have solution u can send me ...please please and also where to see these responses from AT COMMANDS.................
Regards,
Mohan
ThiVu said:
I am also facing with this problem.
This is my command sequence:

send:AT

recv: 6

OK


send:AT+CSQ

recv: 20

+CSQ: 22,0



OK


send:AT+GSV

recv: 65

SIMCOM_Ltd

SIMCOM_SIM908

Revision:1137B03SIM908M64_ST



OK



send:AT+CGPSPWR=1

recv: 6

OK


send:AT+CGPSRST=0

recv: 6

OK


send:AT+CGPSOUT=255

recv: 6

OK


send:AT+CGPSIPR=115200

recv: 6

OK


send:AT+CGPSSTATUS?

recv: 39

+CGPSSTATUS: Location Unknown



OK


send:AT+CGPSINF=32

recv: 67

32,000054.001,V,0.000000,N,0.000000,E,0.00,0.00,10 1010,,E,A

OK

---------------
I received respond form CGPSSTATUS: Location Unknown
And data from CGPSINF seem to be invalid.
Could you help me to solve this.
Maybe I make mistake or forgot some command??
My GPS antenna is placed outside so I dont think the problem come from antenna.
Thank you
Click to expand...
 

first of all you must understand that a microcontroler cannnot send GSM signals to the base station. So there must be a module. such as SIM908 . If you intend to command and control the SIM908 through AT commands you must send the AT commands inside the SIM908 module. this is done via a communication protocol called UART. your microcontroler must have a UART port.
so you connect both UART ports appropriately and send the AT command using UART.
let me know if it helps
 

Please help me

I need help. I used build in charger circuit to charge Li-Ion battery. I put VCC(+4v) to Vchg and Vant_int to supply power module SIM908 and active antenna. But when i try to get location by command "AT+CGPSPWR=1" --> "AT+CGPSRST=0" --> "AT+CGPSINF=0" i got "0,0.000000,0.000000,0.000000,19800105235954.000,0,0,0.000000,0.000000" For command "AT+CGPSSTATUS?" i got "+CGPSSTATUS: Location Unknown" . By googleing other sources i found that build in charger circuit damages the GPS!!!! Is it right ?? Or i miss something please help me!!!!

i'm sorry for my bad english
 

I'm sending AT commands via 68(RXD) and 71(TXD) pins of SIM908 by max232 from PC. I'm doing smth wrong? This is my schematic
 

Attachments

  • board.PDF
    91.5 KB · Views: 149

There is a Button in schematic where the Rx and Tx pins you have used connect. Is it a button or jumper? If it is jumper is it set properly? What baudrates your SIM908 supports? What baudrate you have selected in Hyperterminal or other PC serial software?

Send the Proteus file. I will check it.

You have to use the switch to connect SIM908 to MAX232. It is by default connected to AVR MCU. Good Luck...
 
Last edited:

Button in scheme used for switching between MCU and PC with SIM908. Why you think that my problems is in negotiation with SIM908? if i had smth wrong in UART the SIM908 wouldn't answer for requests. I sending "AT" SIM responses "OK". I'm sending "AT+CGPSPWR=1" it says "OK" then "AT+CGPSRST=0" it says "OK" and i'm asking coordinates like AT+CGPSINF=0 it responses "0,0.000000,0.000000,0.000000,19800105235954.000,0 ,0,0.000000,0.000000"

As i understood if i had bad interface it whouldn't response?
 

Does your GPS has antenna? May be it is not receiving signals. If it receive data then there will be no problem for SIM908 to send it to PC.

- - - Updated - - -

Does your GPS has antenna? May be it is not receiving signals. If it receive data then there will be no problem for SIM908 to send it to PC.

Why you think that my problems is in negotiation with SIM908?
Click to expand...

Because by default your SIM908 or AVR is not connected to MAX232.

AVR is connected to SIM908 by default.

If you change the switch posistion then SIM908 directly connects to MAX232

By default your board works like this

SIM908 communicates with AVR MCU and AVR MCU communicates with PC through USB.

If switch position is changed then SIM908 connects directly to MAX232 for serial communication with PC and AVR is disconnected from SIM908.
 

Yeah you're right switching between AVR and PC was nessesary for me for debuging aims. I'm expected to see how SIM908 works by AT commands then to write some code for AVR. I connected GPS antenna to the left-top of the module.
I used this GPS antenna for my module
http://ru.aliexpress.com/item/1575-...al-antenna-with-IPEX-connector/638772710.html

I'm suspect of damage my sim908 by using it's internal charger interface. Otherwise i think if it's GPS part is brokedown it couldn't response for commands "at+cgpspwr=1"
In previus replys for this post someone says that charging Li ion batterys by buildin charger can kill GPS part of the module, for that reason i have some doubts of it functionality
 

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