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Topic: Using GSM shield with mega 2560, wiring instead of stacking (Read 1 time) previous topic - next topic

MikeCaptnKidd

I got my GMS shield working stacked on an Uno, then got it working with six wires connected instead of stacking.  (Gnd, 5V, Vin, Tx, Rx, Ctrl->7).    The application is for sending and receiving SMS messages, no other functionality needed.

When I try to get it working via wiring on my Mega2560, it won't initialize.  I'm using an Adafruit SD card shield, so digital 10, 11, 12 and 13 are in use.   I've tried using 14 and 15 like this:
  #define __TXPIN__ 14
  #define __RXPIN__ 15
  #define __RXINT__ 14
with no luck. 

Unlike the Uno, this Mega has a separate 5V power supply, so instead of connecting 5V to the Arduino's 5V, I'm connecting it to the external 5V power source.  (All share a common ground.)     I have the CTRL (reset) line connected to Arduino digital 7.

Is it OK to use RXINT and TXPIN on the same line? 

Should the GSM's VIn be connected?  If so, to the Arduino's Vin or 5V line, or to the external 5V? 

MikeCaptnKidd

Fixed, at least for now, and I honestly don't know why.   In case it helps somebody else, here's the configuration that worked:

WIRING
      Modem      Arduino Mega 2560
       GSM TX            digital 50
       GSM RX            digital 51
       CTRL                 digital 7
        VIN                   not connected
         5V                    5V
         GND                GND

Software setting in the __AVR_ATmega2560__ block:
  #define __TXPIN__ 51
  #define __RXPIN__ 50
  #define __RXINT__ 51

This setup uses the Arduino's 5V out as a power source, but it appears to be enough to send and receive SMS messages.

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