How to connect SPI pins on the Leonardo/Yun!? It seems straight-forward but I'm not getting the expected results.
I'm driving a led matrix using SPI and this was going just fine with an Arduino Duemilanove/Uno (ATmega328p), using SPI's MOSI, SCK and SS on digital pins 11, 13 and 10 respectively. So on the Leonardo/Yun (ATmega32u4) things have changed and MOSI and SCK are now only accessible through the ICSP headers. No problem, I'll just use those. But what am I to do about the SS pin? It's my guess that it shouldn't do any harm to just connect it to any digital output as long as it's set to OUTPUT and I can flip it HIGH and LOW as needed. However, I haven't been able to get my led matrix functioning with that approach. The LEDs don't turn on, but there's random flashing throughout the matrix every now and then. Don't have a scope unfortunately. I can drive the matrix with the Leonardo/Yun when just big-banging (sending the 1's and 0's using the digital ports directly instead of using the fast protocol SPI), but I really need the speed of the SPI.
Any tips I should know about? Thanks!