I have an application where I want to collect data on-board from many sensors. The idea I have now is to use an Arduino Mega to allow for enough sensors and use an SD card to store the data. To use the SD card, do I need to buy a sheild? Is there a particular shield i need to get if using the Mega?
The SPI pins on the Mega are in two location, either the six pin ISP connector in the middle of the Mega or pins 50-53 at the end of the Mega.
Many shields that work on Uno such as the Adafruit data logging shield will only work on Mega with software SPI which is slow.
Arduino shields, such as the Ethernet shield, have a SD socket and connect to the ISP connector. The Seeed v4.0 also uses the ISP http://www.seeedstudio.com/depot/SD-Card-Shield-V4-p-1381.html
Some users connect the shield's SPI pins to the Mega SPI pins using extra wires/jumpers.
Any breakout module with level shifters should work. Level shifters convert 5V Arduino SPI signals to 3.3V SD signals.
Have a look at www.2wg.co.nz. That is an arduino application that uses an sd data card to log data in the backup directory of its sd card. You can browse the sd card and see all the files but will only be able to open a few example files in the public directory.
Various web pages show the sensor statistics being captured.
Cheers
Catweazle NZ