Sim900 and Arduino; missing echoing and response

Hello. Using Arduino Nano and Sim900 to Post data from my cabin to webserver and store it in database. Every thing is working fine except when Sim900 is loosing connection to network. I want to test the connection before trying to Post the data but I dont get any echo of AT+ commands neither the response (OK or ERROR) from Sim900. The funny thing is that during setup() function I get both echo and responses.

So all the AT+ commands are working during initiation, Post, and termination of the http connection.

Im using 9600 between Nano and Sim. Echoing is enabled and I have a function to read the data from the Sim(which must be working because I have tellback during setup).

Hope someone can help



Suddenly I thought I had done a terrible mistake. The Nano has 5v I/O and I thought that the Sim900 board had 3.3v I/O for software serial. But after have examined the SIM900 board I found that it had level shifters fitted.

Puuuuuuh.... or????

Well Im back to zero; still needing help



I use two serial connection on the nano and wasnt aware of the conflict between the rx's.

Had to use the Serial.listen() function to select which of the two rx to enable.

Now its working properly..... :-)