I am a rookie to arduino. I am trying to access MQTT server using Sim800l coreboard GSM module with Adafruit Fona/Tinygsm library but failed.So I decided to check http GET/POST request with AT command first.In AT commands all the basic commands following www.exploreembedded.com/wiki/Setting_up_GPRS_with_SIM800L works fine but whenever I make a GET request by "AT+CIPSTART=" module restart itself.by AT commandsI also tried seeduino library GPRS_HTTP example, it gives me "error:CIPSTART" and restarts module.Though this code worked one time only,this is the code

#include <gprs.h>
#include <SoftwareSerial.h>

char http_cmd[] = "GET /media/uploads/mbed_official/hello.txt 
char buffer[512];

GPRS gprs;

void setup() {
Serial.println("GPRS - HTTP Connection Test...");  
while(0 != gprs.init()) {
 Serial.println("init error");
while(!gprs.join("gpinternet")) {  //change "cmnet" to your own APN
  Serial.println("gprs join network error");
// successful DHCP
Serial.print("IP Address is ");

Serial.println("Init success, start to connect mbed.org...");

if(0 == gprs.connectTCP("mbed.org", 80)) {
  Serial.println("connect mbed.org success");
  Serial.println("connect error");

Serial.println("waiting to fetch...");
if(0 == gprs.sendTCPData(http_cmd))

//  gprs.closeTCP();
//  gprs.shutTCP();
//  Serial.println("close");  

void loop() {    


also tried this commands and module got restarted after AT+HTTPACTION=0 this last command enter image description here

module power and sim configure are fine as far I know,please help me find out what am I doing wrong?Sorry for making this long.please ask me if I couldn't make the question clear.TIA

  • How exactly are you powering the SIM800?
    – Majenko
    Commented Sep 17, 2017 at 12:58
  • I have connected a buck booster with arduino 5V pin and got 4V for SIM800l as it works between 3.6-4.2 . also while using AT+CIICR or AT+SAPBR =1,1 command, module blinks continuously until making a GET request I don't know if it is normal or not and then restarts. Commented Sep 17, 2017 at 15:23
  • it can make calls ,send text ,shows network status. doesn't restart then. Commented Sep 17, 2017 at 15:26

1 Answer 1


I get it now , a stable power source is the answer. arduino with usb can give right amount of Volts but it lacks stable power(amps i guess) while making a TCP connection, that's why module keep restarting.Although it works fine with call, text etc. powering arduino with an AC adapter solves my problem ,now it can connect to mqtt too.Thanks

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