[SPI] Many master SS pins on Due?

Hi everyone :open_mouth:

My name is Melissa, I'm new here and hope someone can help me with this.

I am using an Arduino Due and I want to receive a bitstream from many AVR microcontrollers (about 45). I am using the Due as the master device. However the Due's SPI page says it only supports pins 4, 10, and 52 for the master SS line from the Due...I have no idea why this is because AVRs can have almost any I/O pin be an SS line for the master so I decided to try using other pins other than 4, 10 and 52 as master SS lines.

I currently have many other pins acting as SS lines from the Due and it compiled fine but I'm only receiving "0xFFFFFF" on all lines :~, even 4, 10 and 52. I was wondering if anyone knew if the Arduino really does restrict SS lines to 4/10/52 or if its probably some other error. Wanted to rule this out before I went crazy trying to figure out why it wasn't working. I looked all over the internet but couldn't find any information on this. I guess no one has tried to tie 45 AVRs to an Arduino before.

Thanks! I hope this question was clear...


Also on the Due you can use any GPIO pin as an SS pin in master mode but only with pins 4, 10 and 52 you can use the extended SPI API described here: http://arduino.cc/en/Reference/DueExtendedSPI.

What AVR microcontrollers are you connecting to? Do they run on 3V3? If not, are you using level converters?