GPRS Shield

[danofri]

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

Thanks!
Danofri.

[simon_su]

Hello, Danofri

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

Regards,
Simon

[danofri]

@simon su

Hello, Danofri

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

Regards,
Simon

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?

Thanks!
Danofri.

[tmb]

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???

[tmb]

While looking around the Seeedstudio webpage I stumbled across my own answer:

ics.nxp.com/support/documents/in … n97055.pdf

is an NXP app note that explains it all…

(wish I had seen this a couple months ago)

[Steve_Chang]

@tmb@ieee.org

While looking around the Seeedstudio webpage I stumbled across my own answer:

ics.nxp.com/support/documents/in … 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.

Regards,
Steve

[danofri]

@danofri

@simon su

Hello, Danofri

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

Regards,
Simon

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?

Thanks!
Danofri.

Someone?

[tmb]

@danofri

@danofri

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?

Thanks!
Danofri.

Someone?

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:

Arduino board must be able to control the power to GPRS Shield (Issue Type: Necessary Addition)
Right now the GPRS Shield needs to be turned on manually using a switch. In future version, a transistor may be used in parallel with this switch which can be controlled by the Arduino board below to turn the GPRS Shield on. Also the “status” signal which is currently routed to an LED may also be routed to one of the Arduino headers so that the microcontroller on the Arduino compatible board below can sense if the GPRS Shield has turn on or not.

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)