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I am using SIM800L module. I am new to GSM modules. I have searched in many web sites about SIM800L, every where they mentioned baud rate 9600 for SoftwareSerial but it is not working at all in my case. So I started a trail and error method to match baud rate. Finally I found that its baud rate is 38400. With baud rate of 9600 for Arduino and 38400 I am able to communicate with SIM800L.

The problem is that I am unable to register to network. AT+COPS=? shows all available networks. Using AT+COPS="value" I am able to select network. But after that the SIM800L module still blinks every second.

In loop() I am continuously reading software serial and it's printing the following: 

RDY
+CFUN: 1
+CPIN: READY
Call Ready
SMS Ready
RDY
+CFUN: 1
+CPIN: READY
Call Ready
SMS Ready

The above data is continuously printing on console.

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8
  • Sounds like your power supply is browning out due to overloading. What are you powering it with?
    – Majenko
    Commented Nov 27, 2017 at 16:01
  • i am using arduino 5v pin with IC lm317. Output around 4.14 Volts.
    – Subbu
    Commented Nov 28, 2017 at 3:32
  • Tried with 3.7v and 2amps battery, facing same problem. Blinking light every second for four to five seconds after that gap of 3 seconds and again starting blinking.
    – Subbu
    Commented Nov 29, 2017 at 15:47
  • Experiencing this problem, anyone who knows how it was resolved?
    – Mwangi Gilbert
    Commented Jan 3, 2018 at 15:33
  • @Mwangi Gilbert it is because of low current problem, for me solved this problem by parallel connection of more than 2 batteries (it may be of 3.7 to 4.2). Please try this it works.
    – Subbu
    Commented Jan 5, 2018 at 2:42

2 Answers 2

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I am 90% sure it's a power issue. Not sure on what board/module you're using but the SIM800L/SIM900 needs a burst of current of 2 A during 577 µS (See the manual).

Try using 4700 µF and a 10 µF capacitor in parallel with the module. Powering it with a proper power source instead of the Arduino wouldn't hurt too.

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Might be some power issues, but I fixed mine by just trying some AT command

AT+CBAND?

Then, AT+CBAND="DCS_MODE"

That works for me. Give it a try man.

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