RN-XV, SD and magnetometer shield
Part of my plan to make a low-power wifi-enabled magnetometer for AuroraWatch UK. This shield is designed for Calunium, but will work with full functionality on the Arduino Mega2560. It will also operate on a standard Arduino but flow control and some of the GPIO features of the RN-XV are not available.
The shield uses logic level translators on both the inputs and the output from the SD card. This means it can be safely used in situations where there are 5V devices on the SPI bus (eg MicroMag3), see blog.stevemarple.co.uk/2011/10/interfacing-33v-devices-to... for a discussion of the problem.
Eagle design files are available under CC BY-SA 3.0 licence at github.com/stevemarple/RNXV_SD_shield.