I moved the conversation to here:http://arduino.cc/forum/index.php/topic,98850.0.html
This board has a continuous and on demand mode. Send it an "E" command to terminate continuous. Send it a "C" command to get a value periodically say every 10 seconds. Calibration has to be performed with a 7 and 4 or 7 and 10 standard. Do the 7 first as this fixes the intercept then do 4 as this fixes the slope.
I have been trying to communicate with the board by typing the commands in the serial monitor but so far nothing...
I don't know how I did it, but a few days ago, I managed to switch off the LED (on datasheet is says to enter L0 to turn off the LEDs and L1 to turn them back on), but I still cannot manage to either turn the LED on, or reset the board.
the only way I can get a read is by resetting the arduino and unplugging/ replugging the GND on the stamp