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SIM900B GSM Module - no voltage detected on SIM_VDD

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softlab
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2011/12/20 12:48:10 (permalink)
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SIM900B GSM Module - no voltage detected on SIM_VDD

Dear All,

I am using SIM900B Module. Circuit as shown in the attached picture. When Module powered (with SIM CARD Inserted), Netlight Blinks but I didn't find any voltage on VSIM (from SIM_VDD pin of Module). Also, the module didn't registered on Network. PWRKEY Works correctly. Any help would be highly appreciated.

I have used 0.1 uF as decoupling capacitor and SMF05C ESD protection IC and 1000uF, 6.3v cap (for 2A supply when transmission).

thanks 
#1

17 Replies Related Threads

    softlab
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    Re:SIM900B GSM Module - no voltage detected on SIM_VDD 2011/12/20 22:28:21 (permalink)
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    Any help?

    thanks
    #2
    rpg7
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    Re:SIM900B GSM Module - no voltage detected on SIM_VDD 2011/12/21 00:17:32 (permalink)
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    Only thougt is that you either have the wrong pin or bad connection to the SIM. Bear in mind that some modules power up the SIM at 1.8V an look for a reset response. If the don't get it then they try 3v3 and if they don't get that then they power down the SIM. So check the pin with a scope, possibly with a single shot trigger.
    #3
    softlab
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    Re:SIM900B GSM Module - no voltage detected on SIM_VDD 2011/12/21 02:13:57 (permalink)
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    did you see the picture that i have attached? is there anything wrong? 

    thanks
    #4
    rpg7
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    Re:SIM900B GSM Module - no voltage detected on SIM_VDD 2011/12/21 03:03:09 (permalink)
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    softlab

    did you see the picture that i have attached? is there anything wrong? 

    thanks


    Yes. However, it doesn't mean that you don't have dry joints or have fitted an incorrect resistor or capacitor or that you have picked the wrong pin on the module or that there isn't a short circuit on one or more of the module pins. I don't use the module you have chosen so I suggested some generic things to look at.
     
    Have you checked the voltages with a scope?
    #5
    softlab
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    Re:SIM900B GSM Module - no voltage detected on SIM_VDD 2011/12/21 04:17:10 (permalink)
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    Yes. However, it doesn't mean that you don't have dry joints or have fitted an incorrect resistor or capacitor or that you have picked the wrong pin on the module or that there isn't a short circuit on one or more of the module pins. I don't use the module you have chosen so I suggested some generic things to look at.


    I have used all the components exactly as mentioned in the datasheet except one decoupling capacitor (22pf) on SIM_DATA pin. I have used 27pF instead of 22pF that is mentioned in the datasheet.

    Also, I have cross checked all the connections for short circuit/wrong pins. But, everything is OK. I have little bit doubt on SIM CARD connections. If you confirm that the SIM CARD pins connected to the Module is correct, then it will be helpful.

    Have you checked the voltages with a scope?
     
    I don't have scope on my hand. I have only multimeter.

    thanks
    #6
    softlab
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    Re:SIM900B GSM Module - no voltage detected on SIM_VDD 2011/12/21 04:59:04 (permalink)
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    rpg7, Should I short RTS and CTS pins of the GSM Module?

    pl Note: I have not used any serial port pins except RX & TX.

    thanks.
    #7
    softlab
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    Re:SIM900B GSM Module - no voltage detected on SIM_VDD 2011/12/21 21:33:49 (permalink)
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    can anyone help me to solve the problem?

    thanks
    #8
    softlab
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    Re:SIM900B GSM Module - no voltage detected on SIM_VDD 2011/12/22 00:52:53 (permalink)
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    I have tried to access the SIM900B GSM Module from PC using DB9. It works fine. I have changed auto-baud to 9600 bps. I can able to read and write from/to module. I can able to communicate from PIC also. But, the module didn't register on the mobile network. Anyone can help me to identify the issue?

    at the module startup, i received the following message on Hyper Terminal:

    RDY

    +CPIN: NOT INSERTED

    +CFUN: 1

    I strongly believe that problem lies on SIM CARD Pins connected to module. Especially, SIM_VDD pin of SIM_CARD holder. I didn't find any voltages on SIM_VDD pin. I am trying to figure out the issue.

    any help? 
    #9
    DarioG
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    Re:SIM900B GSM Module - no voltage detected on SIM_VDD 2011/12/22 02:51:50 (permalink)
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    I am sorry, I only used A8000 chip for GSM.
    It worked pretty well after some issues with the On/off pin... Smile and then all ok.

    GENOVA :D :D ! GODO
    #10
    softlab
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    Re:SIM900B GSM Module - no voltage detected on SIM_VDD 2011/12/28 23:57:57 (permalink)
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    Hi all,

    As I said earlier, I found that the problem with SIM CARD pin connections. From the SIM CARD pin descriptions in SIM900B datasheet is differed. I corrected the pin connections and also I did the following modifications and now everything works fine.

    1. I replaced one 0.1uf with 220uF electrolytic capacitor.

    2. Short CTS & RTS pins of the module.

    one more suggestion needed in coding.

    Note: I will post, the conflict on the diagram that I found on datasheet, later

    I already communicated SIM300 GSM Modem from PIC16F877A MCU. The following line works well there.

    // copy the Message Number after splitting the line +CMTI: SM, <SMS Mesg Num>
     
    strcpy(SMS_MSG_NUMBER, <SMS Mesg Num>);

    puts("AT+CMGR=");
    puts(SMS_MSG_NUMBER);
    puts(0x0D);

    But, In PIC16(L)F1827, I am getting error. One additional example that I can give you.

    works well in PIC16F877A:

    puts("ATE0");
    puts(0x0D);

    But, in PIC(L)F1827, only the folowing line is valid:

    puts("\rATE0\r");

    I have to read the SMS when I receive the SMS.

    any help?

    thanks
    #11
    DarioG
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    Re:SIM900B GSM Module - no voltage detected on SIM_VDD 2011/12/29 04:23:50 (permalink)
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    If it can help, I can say that C18 library functions for usart used to send ALSO the trailing "0" at the end of the string (not sure if this happens in your compiler too).
    Of course this was crazy in my opinion Smile and would disturb the GSM module: I ended up writing my own puts()...

    GENOVA :D :D ! GODO
    #12
    softlab
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    Re:SIM900B GSM Module - no voltage detected on SIM_VDD 2011/12/29 10:18:59 (permalink)
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    Of course this was crazy in my opinion and would disturb the GSM module:..


    Yes. you are correct. I have written the code in c in Hi-Tech C compiler v9.0 for PIC16F877A. Now, I have updated the older version with new one v9.83. I don't know, this could be a problem and I have to check (uninstall the latest and try with older version) and let you know.

    I ended up writing my own puts()...


    can you give any idea whether should we send trailing "0" at the end of string?

    thanks


    #13
    MarkEHansen
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    Re:SIM900B GSM Module - no voltage detected on SIM_VDD 2011/12/29 16:58:02 (permalink)
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    In general, the null at the end of a string is used to mark the end of the string and is not part of the string itself. Therefore, it should not be sent.

    Of course, unless your communication protocol specifically requires it.


    #14
    DarioG
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    Re:SIM900B GSM Module - no voltage detected on SIM_VDD 2011/12/30 04:07:47 (permalink)
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    Yep, as Mark said.

    My puts ( ) thing is more or less:
    wh ile (*data)
      put ch ar(*d ata++);

    (sorry, needed to put random blanks in there, due to shit-ty forum software...!)

    GENOVA :D :D ! GODO
    #15
    softlab
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    Re:SIM900B GSM Module - no voltage detected on SIM_VDD 2012/01/05 05:27:09 (permalink)
    +2 (1)
    My puts ( ) thing is more or less:
    wh ile (*data)
    put ch ar(*d ata++);


    Thank you dario. Now I can able to send variables using this function without any problem.

    void my_puts(const char * s)
    {
      while(*s)
      putch(*s++);
    }

    I already have communicated SIM300 GSM Modem from PIC16F877A and PIC18F452. Now I have finally moved to PIC16(L)F1827. I have the problem of reading SMS in previous PIC MCUs and also in this MCU. All other AT commands working fine, for example, ATE0, AT+CMGF=1, AT+CLIP, AT+CMGS, etc. But, I have a problem on 2 AT commands. One is AT+CMGR and another one is AT+CLCC. I can able to avoid AT+CLCC command by replacing AT+CLIP command to identify the incoming caller id. So, I have to resolve the issue on AT+CMGR command.

    i.e. When I receive SMS, I can able to receive +CMTI: SM,<Msg Num>. Also I parsed the Msg Num and send it to GSM Module using AT+CMGR=<Msg Num>. I also received the +CMGR:....., <Mobile number>,... correctly but hanged. I have to reset the GSM Module? why? Because of the number of characters exceeds the limit?

    IDE: MPLAB v8.63
    Compiler: Hi-TECH-C v9.83
    PIC MCU: PIC16F1827

    This is the code.
     // GSM VARIABLES
    unsigned char GSM_MODULE_OUTPUT;
    unsigned char gsmOutput[70];
    unsigned char gsmCmdUserInput[10];
    unsigned char substringOfInput[13];
    unsigned char gsm_input[25];
    unsigned char Message_Buffer[20];
    unsigned char storeValuesFor[5];
    unsigned char SMS_MessageNum[3];
    unsigned char OwnerPh[11] = "4444444444";
    unsigned int Message_Store = 0;
    unsigned int a = 0;
    unsigned int c = 0;

    //STRUCTURE TO STORE TELEPHONE BOOK (THE COM OUTPUT)
    typedef struct{
    unsigned char splitWord[23];
    } GSM_output;

    GSM_output GSM_DATA_LINE[2];

    //unsigned int i=0;
    unsigned int counter = 0;
    unsigned int lenOfGSMInput = 0;


     void process_GSM_MODULE_OUTPUT_1(){

    // strcpy(&gsmOutput[0], "0") ;
    if (strlen(gsmOutput) > 5){
    if (strcmp(substring(0, 5, gsmOutput), "+CMTI") == 0){

    strcpy(storeValuesFor, "CMTI");
    split_this(storeValuesFor);
    strcpy(SMS_MessageNum, GSM_DATA_LINE[1].splitWord);
    strcpy(&gsmOutput[0], "0") ;
    strcpy(&storeValuesFor[0], "0");
    // strcpy(gsmCmdUserInput, "");

    Message_Store = 1;

    lcd_clear();
    lcd_goto(0); // select first line
    lcd_puts(SMS_MessageNum);
    __delay_ms(2000);

    putch(0x0D);
    putch(0x0A);
    my_puts("AT+CMGR=");
    my_puts(SMS_MessageNum);
    putch(0x0D);
    putch(0x0A);
    }

    else {
    lcd_clear();
    lcd_goto(0); // select first line
    lcd_puts(gsmOutput);
    }
    }
    else{
    lcd_clear();
    lcd_goto(0); // select first line
    lcd_puts(gsmOutput);
    }
    strcpy(&gsmOutput[0], "0") ;
    }


     	while(1){

    GSM_MODULE_OUTPUT = getch();
    switch(GSM_MODULE_OUTPUT){

    case '\x0A': // if line feed detected in the GSM output i.e. '\n'

    break;
    case '\x0D': // carriage return detected i.e. '\r'

    gsmOutput[i] = '\x00';
    lenOfGSMInput = strlen(gsmOutput);

    if (lenOfGSMInput > 0){

    i = 0;
    lenOfGSMInput = 0;
    process_GSM_MODULE_OUTPUT_1();
    }
    break;
    case '\x3E': // if greater-sign (in order to send SMS)
    if (strcmp(gsmCmdUserInput, "SEND_SMS") == 0){
    strcpy(gsmCmdUserInput, "SMS_SENT");
    lcd_clear();
    lcd_goto(0); // select first line
    lcd_puts("Sending SMS...");
    my_puts("GSM");
    putch(0x1A);
    }
    break;
    default: // if characters received
    if (i < 60){
    gsmOutput[i] = GSM_MODULE_OUTPUT;
    i++;
    }

    break;
    }//end brace for switch
     }

    Any help?
    #16
    israelco
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    Re:SIM900B GSM Module - no voltage detected on SIM_VDD 2012/02/18 16:39:52 (permalink)
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    Hi, I'm very new to this and I'm trying to build a very similar project to yours. I want to control a sim900 module trough a pic16f1827 . a. receive a voice call caller id hang up and check in phone book if exist then open relay for 2 seconds. b. receive sms with code to register new numbers in internal phone-book memory in the pic16f1827. I have no idea where to start. I have a pickit3 and a picdem lab board purchased . i would very appreciate any tips and help given. Thank You!
    #17
    boatbodger
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    Re: SIM900B GSM Module - no voltage detected on SIM_VDD 2017/06/08 15:04:56 (permalink)
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    I too have the "No voltage on SIM_VDD" pin on an SIM808 module.
    Did you ever find out how to get the power to be provided to the SIM?
    I have checked with 'scope, and I don't see power being applied - ever.
    #18
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