Sim 900 GPRS shield pinout

Question

I'm currently working on a project involving a GPRS Shield based on Sim 900 Chip

I was wondering if anyone would know which ones are the VIN Pin and the RING pin ? It doesn't say on the board itself and all other searches have lead me to a dead end.

Also if you have a detailed pin layout it would be much appreciated.

Thank you

The GPRS shield is the one in the link below

https://i.sstatic.net/mzMnA.jpg

Answer 1

Ring Pin

If you have a Multimeter with continuity testing, check where the RI pin (#4) on the Sim 900 chip is broken out to. Here is an overview of the pins:

If it isn't (some shields don't have them broken out) you could solder a wire to the RI pin with an LED and resistor to Ground, something like this:

[RI Pin]--------[wire]--------[LED]--------[Resistor (330Ohms?)]--------[Ground]

The ring indicator is HIGH by default and LOW when there is an incoming call. So, when there is no call the LED is on and off when there is an incoming call.

---

VIN

When the position of the switch (middle left in the image below) is set to "extern" (right), you have to supply power to the barrel connector. When you set the switch to the left position, the module takes power from the 5V pin of the arduino OR (dont attach both!) an external power supply you attach to that pin.

Hope it helps :)

PS: These SIM modules can have current peaks up to 2 Amps. I recommend you to use an external power source that can provide minimum 2A at 5V.

Edit:

This might be helpful: http://wiki.seeed.cc/GPRS_Shield_v1.0/. I think its the same module as yours. Have a look at the "GPRS Shield v1.4 Schematic" at the bottom of the page.

Edit 2:

Comparing the board from the link and yours, i'm very certain that the ring pin is the one marked in red in the image above. Checking with a multimeter doesnt hurt though. You can add the same circuit i described above to that pin to add an LED indicator.