Sim800L keeps transmitting garbage Values


I recently bought a SIM800L module, and am having a REALLY HARD time getting it to work. The connections to the module are as follows:

Vcc = LM2596 Buck module with source 12vDC 2Amps and output 4.0v DC.
Gnd =Gnd
TX = Arduino RX
RX = Arduino TX (Through a voltage divider where Output = 2.8v)

Now the SIM800L TX pin keeps on transmitting garbage values even the power supply is not connected to the SIM800 Module. When the power supply is connected, it starts to transmit even more garbage values (ASCII, Reverse Question Marks, Spades, etc).

I’ve tried all the baud rates from 9600-115200. How can I fix this?



According to your connections and wiring i can see you have done it right, I have personally never used the voltage divider for the gsm Module so i cant say if in any way that’s giving you any issue.

other than that i will recommend you to use this software , I have personally used it a lot when i face such issues. it has the Auto Baud Detection setting too where it automatically checks all the baud rates, as i can see the only problem here is the baud rate. and still if nothing works. try Swapping The RX and TX of the GSM.

Do Let me know if anything works.

Parth Temkar


The voltage divider is not a good idea. Use a standard level translator shown in SIMCOM datasheets or use a chip like TXS0102.

The Garbage values can also be due to improper ground connections. Double check it.