Arduino Uno as SPI slave

Projects Networking, Protocols, and Devices
4

I tried goin in reverse now, using UNO as the master and SAMD as the slave. But again I'm running in to problems. I used this code for the SAMD21 slave. And this for the master:

#include <SPI.h>
#include<Arduino.h>

void setup (void)
  {
  digitalWrite(SS, HIGH);  // ensure SS stays high
  SPI.begin ();
  SPI.setClockDivider(SPI_CLOCK_DIV4);    //Sets clock for SPI communication at 8 (16/8=2Mhz)
  Serial.begin(115200);
  } // end of setup

void loop (void)
  {
  byte c;

  // enable Slave Select
  digitalWrite(SS, LOW);    // SS is pin 10

  // send test string
  for (const char * p = "Fab" ; c = *p; p++)
    SPI.transfer (c);

  // disable Slave Select
  digitalWrite(SS, HIGH);
  delay (100);
  } // end of loop

I tried changing the clock div to all values but it doesn't help, any hints on what is wrong assuming the connections are correct?

In addition to that I tried sending from SAMD21 to SAMD21 using the code that worked after lowering frequency but the slave never gets any data.