I don't know about the external power. Have you tried the GSM shield without the ethernet shield connected?
I do know that most usb ports will provide a maximum of 500ma.
I don't know about using the Mega setting. That sounds like a bad idea to me. Maybe you are running out of SRAM in the Uno?
I had checked the sketch size hit 87% and memory usage hit 77% for UNO.
I had try external power source but still the same result.
The Gsm shield can send message out it just that i cannot get the get / print the value i wanted .
Any idea? I had spent whole day but donno why i cannot get the actual result printed.
Hi SurferTim ,
I figure out the problem, I guess memory cannot hit more than 70% or else it will printed the inaccurate result. Again thanks for the great information and support.