user47548: I bought a GSM module, and I want to connect it with Arduino but I have a problem.
I linked GSM SIM800L with regular LM2596 12 V 2 VA I changed tension to 5 V, So far the GSM is working but if I connect TX_ARDUINO with RX_GSM the module enters in the loop of the restart. 
The picture explains the montage.


user30341: 
Follow this tutorial on how to connect your Sim800l with Arduino.

47548: <p>I bought a GSM module, and I want to connect it with Arduino but I have a problem.</p>

<p>I linked GSM SIM800L with regular LM2596 12&nbsp;V 2&nbsp;VA I changed tension to 5&nbsp;V, So far the GSM is working but if I connect TX_ARDUINO with RX_GSM the module enters in the loop of the restart. </p>

<p>The picture explains the montage.</p>

<p><a href="https://i.stack.imgur.com/QGeI6.png" rel="nofollow noreferrer" title="Fritzing of LM2596, SIM800L and Arduino Uno"><img src="https://i.stack.imgur.com/QGeI6.png" alt="Fritzing of LM2596, SIM800L and Arduino Uno" title="Fritzing of LM2596, SIM800L and Arduino Uno"></a></p>
 30341: <p><a href="https://i.stack.imgur.com/tWSY5.jpg" rel="nofollow noreferrer"><img src="https://i.stack.imgur.com/tWSY5.jpg" alt="Arduino Sim800l"></a></p>

<p>Follow <a href="https://www.teachmemicro.com/arduino-sim800l-tutorial/" rel="nofollow noreferrer">this tutorial</a> on how to connect your Sim800l with Arduino.</p>
