TC35 GSM modem wiring to Arduino UNO


Recently I have bought GSM modem, I connected it to power, inserted SIM card and it worked well (the yellow led flashing short on / long off) which mean it registered on the network.

Now I still cant communicate with Arduino UNO so I can send SMS.

Can someone help telling me the wiring (pins in GSM and where to connect to Aruino) because there are no label on the pins of the GSM. Also, I will appreciated to tell if any voltage leveling in between because I saw pins with 2.65v in the specs.

Many thanks in advance


Wiring with GSM modem is very easy, you just need to connect these pins:

GSM Modem Arduino Rx --> Tx Tx --> Rx GND --> GND

I think no one can make mistake in connecting these wires.

Do check the voltage level of Modem properly. If its not 5V(at which Arduino works), then i may damage either of your device(unless there is a voltage level converter).

Thank you for taking time to reply.

When I checked the pin diagram I found more than TX and RX ( TX_35_TTL, TX_PC_TTL, TX_232_TTL, TX_MCU_TTL - also for RX the same) so I am confused which one of them I have to use.

I tried the TX_MCU_TTL, RX_MCU_TTL with voltage level converter, but it didn't work :(

I am afraid I damaged the modem ...

Though I have not used TC35 modem, I have succesfully made a project with a GSM modem.

After studying the datasheet, I think you should use TX_232_TTL terminals.