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I am trying to make an HTTP request in two ways

  1. Connecting sim900 to pc using TTL converter (without external power, only USB power)

  2. Connecting sim900 using Arduino nano (tried with and without external power, with common ground)

in the first case, everything is ok but in the second case after sending AT+HTTPACTION= the module resets

Arduino sketch

#include <SoftwareSerial.h>
SoftwareSerial sim900(3, 2);

void setup() {
  Serial.begin(9600);
  sim900.begin(9600);
}

void loop() {
  if (sim900.available())
    Serial.write(sim900.read());
  if (Serial.available())
    sim900.write(Serial.read());
}

Serial monitor:

AT

OK
AT+SAPBR=1,1

OK
AT+HTTPINIT

OK
AT+HTTPPARA="URL","http://veterok.xyz:8888/service/time"

OK
AT+HTTPACTION=0

OK
⸮⸮⸮⸮
RDY

+CFUN: 1

+CPIN: READY

Call Ready

power from arduino

external power

  • how are you powering the sim900? – jsotola Mar 21 at 23:47
  • @jsotola I've updated the question, I tried with external power (5V ~12W) and power from Arduino – JVic Mar 21 at 23:48
  • 1
    Your code SoftwareSerial sim900(3, 2); means D3 is Rx, which means that it should connect to SIM900A's Tx, but your wiring diagram connect to SIM900A's Rx. – hcheung Mar 23 at 3:18

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