SPI between 2 Arduinos one as master and one as slave

Projects Programming
10

I made the modification to use two separate SPI.transfer operations with a delay of various values (20 microseconds to 200 microseconds) on the master (see below), however, when I'm printing the byte received from the Slave it's consistently a null. The data sent from the slave to master doesn't seem to be getting transferred:

/* SPI Master - Hello World (derived from Nick Gammon's samples)

Arduino Mega is acting as an SPI Master for 
a corresponding Arduino Mega board

Circuit:
 SS_PIN: pin 53
 MISO: pin 50
 MOSI: pin 51
 SCK: pin 52

*/

#include <stdlib.h>
#include <SPI.h>

long int count = 1;
byte config = B01010000;
#define SCK_PIN  52
#define MISO_PIN 50
#define MOSI_PIN 51
#define SS_PIN   53
uint8_t buffer[128];
char respBuffer[100];
volatile byte pos;
volatile boolean process_it;

void setup()
{
  byte tmp;
  
  // Put SCK, MOSI, SS pins into output mode
  // also put SCK, MOSI into LOW state, and SS into HIGH state.
  // Then put SPI hardware into Master mode and turn SPI on
  pinMode(MOSI_PIN, OUTPUT);
  pinMode(MISO_PIN, INPUT);
  pinMode(SCK_PIN, OUTPUT);
  pinMode(SS_PIN, OUTPUT);
  
  digitalWrite(SS_PIN, HIGH);  // Ensure SS stays high for now
  
  SPI.begin();
  SPI.setClockDivider(SPI_CLOCK_DIV16);
  //SPI.setBitOrder(MSBFIRST);
  //SPI.setDataMode(SPI_MODE0);
  
  SPCR = (1<<SPE)|(1<<MSTR)|(1<<SPR1);
  byte clr;
  clr=SPSR;
  clr=SPDR;
  
  Serial.begin(115200);
}

byte transferAndWait(const byte what)
{
  byte a;

  SPI.transfer(what);
  delayMicroseconds(20);
  a=SPI.transfer(0);
  return a;
} // end of transferAndWait

void loop()
{
 char c;
 byte r;

 // enable Slave Select  
 digitalWrite(SS_PIN, LOW);
   
 pos=0;
 // Send test string
 for (const char *p="Hello, world!\n";c=*p;p++)
 {
   //SPI.transfer(c);
   r=transferAndWait(c);
   respBuffer[pos++]=r;
   Serial.print(c);
   Serial.print(r);
 }
 
 //respBuffer[pos]=0;
 Serial.println("RX:");
 Serial.println(pos,DEC);
 Serial.println(respBuffer);
 pos=0;
   
 delay(100);
 
 // Disable slave select
 digitalWrite(SS_PIN, HIGH);
 
 // 1 second delay
 delay(100);
   
}