SIM800L Ring pin is always low

Hi,
I'm having a problem with SIM800L module's ring pin. It is always reading low. I'm not sure if the pin is actually broken, or if there's some configuration option that I am missing.

Any help would be greatly appreciated.

I could not find what I was looking for but I will take a SWAG and say it needs a pull up resistor. Can you post a schematic, not a frizzy thing showing power and ground connections as well as the power supply capacity. Be sure all grounds are connected.

Here's my schematic. I tried using a pull up resistor, but that didn't do anything (except now the ring pin reads always high). It was worth the try though. I'm using a 3 A power supply and a voltage regulator rated for 3 A. I can send and receive messages without problem, so there should be enough power.

That is what I would expect. The ring pulse is 120 ms in length. You have the ring connected to D2, which can generate an interrupt to the micro. You need to write an ISR (Interrupt Service Routine) and enable the interrupt. To do it properly your ISR should set a flag and you process and clear the flag in your main code. Remember the flag has to be global.

But the problem is, there is no pulse. I was wondering if there is a setting to enable the ring pulse, or is the gsm module broken.

How do you know there is no pulse? You need a scope, or if you are real lucky a LED might show it. With the interrupt trigger on the falling edge.

Yep, I used an oscilloscope. No pulse.

If you are sure it should be pulsing then you have a bad module or a bad connection.