Problems getting SPI to work on Yun (and Leonardo too for that matter)

Hardware Arduino Yún
#1

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!

#2

The Yun/Leonardo is not an Uno -- the SPI pins can only be found on the ICSP header on the "Yunardo".

#3

ericwertz:
The Yun/Leonardo is not an Uno -- the SPI pins can only be found on the ICSP header on the "Yunardo".

Yes, this I know. I apologize for not having expressed my issues better. I'm aware that the SPI parts MOSI and SCLK are on the ICSP headers of the Yun, however it wasn't clear to me what then to do with the SS (slave select) pin, which is on pin 10 on an Uno but on pin.... ???? of the Yun. I do see it on the left side of the image below, which would make SS present on pin 8 of the ATmega32u4 chip but apparently not broken out to a pin header but only used for RXLED???
My question would be: can I use just any other digital pin for Slave Select or must it be the hardware port SS in order for me to succesfully use the MOSI and SLCK ports?

#4