Friday, January 3, 2014

Shileds FAIL with Arduino Mega.

Shortly after the astounding success of my garage parking sensor, I decided to try my luck with something that on its face should have been really really really easy.  I wanted to play with some 'Shields'.  For those of you who have not yet played with Arduinos - shields are small boards designed to easily plug on top of an Arduino to provide additional capabilities.  They can theoretically stack on top of each other.
A Stack of Shields
GPRS Shield
SD Card Shield


I wanted to install a GPRS module on top of my Arduino Mega 2650.  Should have been a piece of cake.  I got a small SIM adapter (little plastic holder that allows the small modern SIM cards to be inserted into the SIM card holders designed for full-size cards) , pulled the card out of my AT&T HTC One and put it in the GPRS module.  Then as instructed on SeedStudio's Wiki I plugged my shield into the Arduino, downloaded and installed the example....  And nothing happened.  I re-read the instructions.  Tweaked stuff.  Nothing happened.  I googled hard.  Nothing useful.Nothing useful. 

Not quite true.  The GPRS Shield has a red light and a green light.  The red light shows the unit is ready.  The green light blinks fast when the unit is first turned on and then starts blinking slowly when network connection is established.  This happened.  This, however, should have been accompanied by output on the serial terminal.  Which never ever happened.  I thought I had a defective unit. 

For Christmas I had bought a friend a Mega and a GPRS shield as well in the hope of a joined project.  And when swapping components we did not achieve success, I felt there was something fundamental missing. 

I gave up after a couple of evenings of frustration.  My friend did not get it either.  I will describe the solution is a follow up post.  After we talk about the SD Shield in the next post.

Hint: It has to do with Arduino MEGA being just a little different, from other Arduino...  Not that anyone would ever tell you that...