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Arduino to GSM module

tonic

I am trying to connect an Arduino Uno with an GSM/GPRS modem which will power up at an voltage supply of 24v, so if a communication is established between both there wont be any problem with voltage level right?

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  • I think we need a little more info. Such as what it the make/model of the modem. What is the method of connection, etc...

     

    If the modem requires 24v to operate it may be because the interface is  RS-232RS-232 serial which can have a+3+15 v requirement for a logic high and-15-3 volts for a logic 0 Many implementations would use 12v for a high and-12 v for a low which is why the 24 volts made me think of this

     

    The arduino will provide a ttl serial signal by default, which will not be adequate to drive rs 232 signals.

     

    But, as I say, we need more info.

     

     

    Mike

  • in reply to mconners

    It is an Calixto-Telit GL86x GSM/GPRS modem.... The method of connection is Tx and Rx pins of Arduino uno are connected to receive and transmit pins of GSM modem through an MAX232 IC... Plz reply...

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  • in reply to tonic

    I thought The MAX232 IC was the greatest thing since sliced bread back when it was released. The ability to create an rs232 connection from a single 5 v supply was a great innovation. The connection you describe should absolutely work.

     

    I'm not sure what your experience with troubleshooting rs232 connections is, so there are some things you might need to check.

     

    Research a null modem cable. Sometimes all you need is tx, rx, and gnd to be connected between the 2 devices. But there is some equipment that requires the rts, cts, dsr, and dtr signals to either be connected, or looped back. If this is the case, I would expect it to be more on the modem side, rather than the arduino/max232 side.

     

    As a test,you could try looping tx and rx together on the max 232 chip and see if on the arduino you can receive what you are transmitting.

     

    You can even back that up to the arduino, loop the tx and rx back on the arduino, make sure that works, then add the max232 into the picture and loop that back, that way you know your side of the equation is working.

     

    Your original question was about voltage levels, with the MAX232 in between the arduino and the modem, there should be no issue, the max 232 will take care of the conversion from TTL levels to RS232 levels and back.

     

    Good luck,

     

    Mike

  • in reply to tonic

    Not a problem, let us know how it works out for you.

     

    Mike