SPI communication Problem Arduino
Why not use I2C slave-master between arduinos?  You can hook up other arduinos or devices on I2C simultaneously (as long as each uses a distinct address).

And you still keep the SPI for a microsd card adapter, for example.

Follow this official tutorial:



MASTER ARDUINO 1

// Wire Master Writer
// by Nicholas Zambetti &lt;http://www.zambetti.com&gt;

// Demonstrates use of the Wire library
// Writes data to an I2C/TWI slave device
// Refer to the "Wire Slave Receiver" example for use with this

// Created 29 March 2006

// This example code is in the public domain.


#include &lt;Wire.h&gt;

void setup() {
  Wire.begin(); // join i2c bus (address optional for master)
}

byte x = 0;

void loop() {
  Wire.beginTransmission(8); // transmit to device #8
  Wire.write("x is ");        // sends five bytes
  Wire.write(x);              // sends one byte
  Wire.endTransmission();    // stop transmitting

  x++;
  delay(500);
}


SLAVE ARDUINO 2

// Wire Slave Receiver
// by Nicholas Zambetti &lt;http://www.zambetti.com&gt;

// Demonstrates use of the Wire library
// Receives data as an I2C/TWI slave device
// Refer to the "Wire Master Writer" example for use with this

// Created 29 March 2006

// This example code is in the public domain.


#include &lt;Wire.h&gt;

void setup() {
  Wire.begin(8);                // join i2c bus with address #8
  Wire.onReceive(receiveEvent); // register event
  Serial.begin(9600);           // start serial for output
}

void loop() {
  delay(100);
}

// function that executes whenever data is received from master
// this function is registered as an event, see setup()
void receiveEvent(int howMany) {
  while (1 &lt; Wire.available()) { // loop through all but the last
    char c = Wire.read(); // receive byte as a character
    Serial.print(c);         // print the character
  }
  int x = Wire.read();    // receive byte as an integer
  Serial.println(x);         // print the integer
}


This is an alternative example of a setup using a nodemcu (which doesnt function in slave mode, btw).