If you are using Flip&Click (Arduino Duo) mikroBUS "B" chip select (CS pin) for SPI and you have problem, try to set it as:

#define mikroBUS_B_CS 87

That pin assigment can be used for A29 or C26.

For more information take a look at the Arduino IDE and manual for ATSAM3:

http://www.atmel.com/Images/Atmel-11057-32-bit-Cortex-M3-Microcontroller-SAM3X-SAM3A_Datasheet.pdf