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  1. #1
    Join Date
    Oct 2008
    Posts
    65

    Default Help interface BenQ GSM Modem to IC16F62A

    I got a BenQ Gsm Modem, so far I got it running sending AT commands from PC to GSM module via hyperterminal using USB to serial converter. The GSM module is operates in 3.3v, Pic16F628A on 5v.
    Questions:
    1.] Obviously I going to need a voltage divider between the module and PIC, but how can I or can Imake Pic16F628A operate on a 3.3v, based on the datasheet in can operates 2.0-5.5v

    2.] I want to try using the following setup connection(refer to the attach image) and the code below..
    Code:
    Include "modedefs.bas"	' Include serial modes
    'Definitions
    DEFINE OSC 4			'for 4 Mhz
    'DEFINE OSC 8			'for 8 Mhz
    
    DEFINE HSER_TXSTA 20h	'hardware assign
    
    DEFINE HSER_RCSTA 90h	'
    
    DEFINE HSER_BAUD 9600	'for 9600 Baud rate
    
    DEFINE HSER_SPBRG 12	'
    
    DEFINE HSER_CLROERR 1	'
    
    TRISB=%00000000
    PORTB=%00000000
    
    ' Send signal tp PWON
        HIGH PORTB.7
        PAUSE 500
        Low PORTB.7
        PAUSE 3000
       
    start:
    HSEROUT ["AT",13]                    'Send AT to modem followed by a CR
    HSERIN 5000, start, [WAIT("OK")] ' wait 5sec to reply.
    PAUSE 1000
    
    goto start
    End
    Where it simply waits for 'OK'. Can I use PortC.6 (with max232) to COM Port at the same time?

    thanks,
    mbox
    Attached Images Attached Images  

  2. #2
    Join Date
    May 2008
    Location
    Italy
    Posts
    789

    Default

    Where it simply waits for 'OK'. Can I use PortC.6 (with max232) to COM Port at the same time?
    You better not!

    I suggest you to use a devider also for the PWON input.

    Cheers

    Al.
    All progress began with an idea

  3. #3
    Join Date
    Oct 2008
    Posts
    65

    Default

    Hi Aratti, thanks for replying...
    I suggest you to use a devider also for the PWON input.
    do you mean to place another 3k3 to PWON and Gnd? Do you think if I use 3.3v to PIC16F628A will communicate well to the GSM module? I tried to supply the mcu with 3.3v with blinking program on PortB.0 but using the voltage meter no deflection shown.
    Please help.....

    regards,
    joe

  4. #4
    Join Date
    May 2008
    Location
    Italy
    Posts
    789

    Default

    do you mean to place another 3k3 to PWON and Gnd?
    Yes

    if I use 3.3v to PIC16F628A will communicate well to the GSM module?
    Yes

    I tried to supply the mcu with 3.3v with blinking program on PortB.0 but using the voltage meter no deflection shown.
    Did you disable brown-out reset feature?

    Naturally if you use 3.3V you don't need the devider!


    Cheers

    Al.
    All progress began with an idea

  5. #5
    Join Date
    Oct 2008
    Posts
    65

    Default

    sorry I've been away for awhile,been busy at work.
    Did you disable brown-out reset feature?
    Now it works great! I got to try it on with the GSM (wish me luck)
    BTW I noticed that when I used USB to UART (Serial TTL) Converter... I did this to display data to my serial communicator, the power from PC provide 4.5v to my PIC. Funny because even I remove the 3.3v supply for the pic to run the blinky program, it still runs, I think the pc provides the voltage to keep it going.
    Could this mean that if I Connect the GSM (3.3v) and connect a USB to UART it will provide 4.5v not 3.3v that could harm the GSM? Please give advice. I need the PC to see what I'm doing.

    regards,
    mbox

  6. #6
    Join Date
    May 2008
    Location
    Italy
    Posts
    789

    Default

    Could this mean that if I Connect the GSM (3.3v) and connect a USB to UART it will provide 4.5v not 3.3v that could harm the GSM?
    Yes, You can safely obtain up to 100 mA from the USB port and use it to power your device. In case you will need 3.3 V you have to use a voltage regulator to drop it from 5V to 3.3 V


    .... Please give advice. I need the PC to see what I'm doing.
    If you want to connect your system to the PC via RS232 port then you should use a level translator as MAX3223, which will convert RS232 level to 3.3 V TTL and vice-versa. Without it you will fry your modem input line.

    Cheers


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    Al.
    All progress began with an idea

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