Using A7 GSM/GPRS/GPS Modem from AI-Thinker with Arduino Mega


I have connected WHDTS A7 GSM GPRS GPS modem by AI-Thinker to Arduino Mega via Tx3 and Rx3 and set baud rate to 115200. Modem is powered by 5V from Mega and Mega is powered by a 12V external adapter capable of supplying 1 amp momentarily. GPS output TxD is connected to Serial1 port (Rx1) of Mega and its baud rate is 9600.

Modem responds to AT commands and when GPS is enabled, GPS data is available on modem Tx/Rx as well as on GPS output correctly.

When modem is reset, it gives following unsolicited responses on screen:
^CINIT: 1, 0, 0
^CINIT: 2, 32, 41891
^STN: 38
^CINIT: 4, 8192, 38
^CINIT: 8, 2048, 1
^CINIT: 16, 0, 1638430
^CINIT: 32, 0, 0
+CREG: 0
+CIEV: service, 0
+CIEV: roam, 0
+CREG: 3

It seems that the modem is not registering on network service provider. It gives error on most of the AT commands pertaining to dialling or SMS.

I have used a prepaid 4GLTE SIM from The network service provider for this vendor is T-Mobile. The SIM is working sending and receiving voice calls and SMS on a standard smartphone (Panasonic). It does not require any PIN. But it is not working with the modem.

What is to be done to make this modem compatible with this SIM/ T-Mobile service provider? Is this modem compatible with 4GLTE service or it can work only with 2G or 3G service?

I am raising this issue with modem supplier also but if this issue has been faced and solved by someone on this list, I will be very happy to learn from him/her.

Please help.

Hi pwddandekar,
I am facing the exact same problem...
By any chance, have you found a solution?

Hi, could you pls provide your sample sketch ? I'm trying to get anything from the board but I did not succeed yet. I suppose to have the same problem because I powered the module standalone with a 4G SIM unlocked inserted. I tried to call the number in the module but the telco operator said the number was not reachable. I got strange numbers at different baud rates but nothing significant. Pls cooperate. THANKS