I got some information from the support (inline), it has helped a bit but it is still not running 
I connected the GPRSBee and the Seeeduino Stalker as described on the page http://www.gprsbee.com/ > Examples > Connecting the GPRSbee to the Stalker board. But power only via USB, no LiPo.
BUT I did NOT wire Arduino D6 to XBee 9/DTR.
Then I connected the Seeeduino Stalker as described here:
Seeeduino Stalker v2.3 | Seeed Studio Wiki to the computer's USB port.
GPRSBee -Support wrote:
- DTR
To swithc the GPRS on in software you have to wire a digital line to the
DTR port of the bee slot. In the example we have used pin 6
If you have the dtr line wired, you can switch it on by software, otherwise
you have to switch it on manually.
Did I get this right I have to solder a wire from XBee 9/DTR to Arduino D6?? I am really surprised about that because I thought GPRSBee was assembled especially for the Stalker and now I need flying wires to get the most basic thing--switching on--done! I would have expected a out of the box working unit. Pfff, interesting! I had now a look at the Seeduino Eagle files and really nearly no pin from the XBee socket is connected to any Arduino pin. I don't understand this. You could work with solder bridges to make it flexible if you not like to use it but in this case it is odd.
So I took a piece of wire and mad a physical connection. Now really software "switching on" is possible, wow! But the next headache came:
void GPRS_software_on_off(){
digitalWrite(PWR,HIGH);
delay(2500);
digitalWrite(PWR,LOW);
}
means not to switch the SIM900 on, if it is already running it is a "off switch" instead of "on". Should I simply check with AT > OK if GPRS is still running? Or is there a better way?
I thought about using Arduino's pin D5, on the Stalker it is prepared to switch VCC for the XBee socket, you can enable it with a solder bridge:
By default EN is connected to VCC to always power xbee. If you want to control the xbee power with digital pin 5(PD5) of microcontroller, just put a solder blob between EN and PD5. Conversely, if you want xbee is always available default to be powered, cut the solder you had put.
But in this case the GPRSBee has to be on as it gets powered and has not to wait for DTR to start. Can I program the GPRSBee / SIM900 to react in this case. This would be also a super default setting so annoying "switching on problems" would not appear.
Here are a couple of hints:
- The RX/TX pin of the Stalkerboard are shared with the UART programming
port (pin 0 and 1). This means that you can not use the uart interface for
debugging, but rather should you use a software serial.
(in the above sketch we use pin 7 and 8).
Sorry, nothing happened! Hardware setting as described above. I use the sketch http://www.gprsbee.com/ > Examples > Test Sketch.
If the LED flashes the GPRSbee is on. You can then send AT commands to it,
to which it should respond.
LED is flashing, means GPRSBee is ready, or?
just sending AT should echo an OK.
Note that the first AT command you send should be in capitals (we normally
use capitals for all AT commands).
I open the Arduino's serial monitor, baud rate is same as in the sketch and I type "AT" but I get no "OK", no other feedback! No ""GPRS on/off".
- Are the pins ok for the Stalker? There are limitations for the Mega:
http://arduino.cc/en/Reference/SoftwareSerial
- Do I have to specify the linebreak? do I have to enter something like \n?
- can an IDE >= 1.0 can this be the problem?? I used 1.5.5
- Do I need to wire additional pins? In your lib there is use of the CTS pin, Do I use solder this or any other pin?
Do someone have any idea? I do not understand why it is not working while it is "Compatible with Seeedstudio Stalker" and I really use only the provided code, no modifications, no tweaks ...
