Hello community. I face a lot of problems using this module and maybe someone can help me or give some advice for a better module.
First the module is exactly this one: (https://goo.gl/m7Jf6t)
Reading an intro guide it said to put a cap here (https://goo.gl/WPwCFQ) to abilitate Software Serial.
Can someone explain it to me what Software Serial is and why do I have to wire these pins?
After did that I download some examples code, connect the SIM900 to power source and attach the right pin to arduino and it works, ok cool and super.
Now my project: turn on a LED into my car through a simple ON/OFF message, so in order to achieve that I grab a Relay, a led , the SIM900 and the Arduino. I wired them all togheter and SIM900 doesnt read the message anymore, it return "???" instead of the right message.
After some tests I think it fault of the synch between arduino and SIM900 because Arduino at setup() function sets the SIM900 to received messages with this code
SIM900.begin(19200);
// Give time to your GSM shield log on to network
delay(10000);
// AT command to set SIM900 to SMS mode
SIM900.println("AT+CMGF=1\r");
delay(100);
// Set module to send SMS data to serial out upon receipt
SIM900.println("AT+CNMI=2,2,0,0,0\r");
So I start looking for "How turn on SIM900 through Software and found out that I just need to solder these 2 resistance (https://goo.gl/gqwFmW) togheter. I did it and tried again and now I have only the possibility to turn on SIM900 using software so I atach it upon the Arduino and when I start it, SIM900 just blink 3/4 times and then It reboot in loop.
I made several tests and when it is attach directly to an external power source it works perfectly instead when it is attach to arduino or between the external source and SIM900 there is a relay it doesnt work, seems like it doesn't receive enough Amperes.
So I made one last test: cut the source wire and directly connect to my tester (dangerously) and surprise, when I turn it on it made the same, 3/4 blinks and then reboot in loop, as soon as I removed the tester and reattach the wire It works!
I dont know what is the problem!
If anybody are actually using or has used this module please give me an help, super appreciate!