SPI connector pinout
For the interconnect between the SPI masters and the SPI expansion boards BitWizard uses a 6-pin SPI cable.
The pinout is the same (or very similar) to the pinout of the 6-pin ICSP programming connector that lots of AVR boards have.
|1||MISO||Master In Slave Out|
|4||MOSI||Master Out Slave In.|
The connector is laid out as follows:
The board usually has pin 1 and six marked.
Connecting the bitwizard boards to an Arduino
You could use other pins, but then you have to make a software SPI implementation. This is not too difficult, but might be neccesary if something else is already on the SPI pins. On the other hand, you might be able to still use the hardware SPI module by just moving the "SS" pin somewhere else.