GPRS Shield

Does this shield supports Arduino Mega?
Does it need a dedicated power input or it can use Arduino’s?


Hello, Danofri

This shield supports Arduino Mega ,and it can use Arduino’s power.
For more imformation, you can reference here.


Thanks Simon,

I have another 2 questions:

  1. My arduino is running using 12V, will it be OK for the shield?
  2. I can see that the shield only have few digital pins, while my Arduino mega has a lot.
    How it is going to work?


Hi Everybody!

I was thinking of picking up one of these shields and was looking over the schematic. The level shifter circuit for the serial connection has me confused a bit.

The gates are tied to VDD_EXT, rx and tx from the SIM900 tied to the sources, and the rx & tx to the Arduino tied to the drains.

rx & tx are opposite direction, but you have them wired the same.

Could someone please explain how this works???

While looking around the Seeedstudio webpage I stumbled across my own answer: … n97055.pdf

is an NXP app note that explains it all…

(wish I had seen this a couple months ago)

Thanks for your sharing, that’s what we have been using on most of our products.



I was just reading SIM900_AN_RDG_V101.pdf and it indicates that if your using a 12v supply you should be using a dc-dc converter. Otherwise, the inefficiency of a LDO regulator will generate too much heat.

As to your second question. I’d say that would work rather well. You’ll have lots of I/O pins to use for other things. (lots of pins on the shield and few pins on the Arduino would be a problem)

In other news, I received the GPRS shield I ordered. I’m presently on a service trip to Mexico, so I won’t be able to play with it for a while. Hopefully I’ll have it up and running by next weekend.

one more item, from the issue tracker on the GPRS shields web page:

for controlling power, the design guide talks about either a p-channel mosfet with a 100k resistor across the pins the button are presently attached to, or using an N channel transistor with three resistors. The guide actually recommends using the n channel transistor rather than the mosfet.

for detecting the output from the status line, would the mosfet method discussed in my last post be a good way of doing it? (it looks like it would, but reading that app note still makes my brain hurt)