Configure Nano Every as SPI - SLAVE (with Example)

Projects Networking, Protocols, and Devices
1

Arduino Nano Every Example: "Configure Nano Every as SPI - SLAVE"

I was searching for a solution for Arduino Nano Every to set it up as SPI Slave, but I was not able to find a working C-Code (like copy paste) for this deadicated MCU.

Therefore, I've tried it out with two Arduino Nano Every Boards by myself and I could figure out a ready to use solution:

Connection overview:
Master <-> Slave
SCK (D13) <-> SCK (D13)
MISO / CIPO (D12) <-> MISO / CIPO (D12)
MOSI / COPI (D11) <-> MOSI / COPI (D11)
CS / SS (D8) <-> CS / SS (D8)
GND <-> GND

Both Arduino Boards are connected to the PC (with 2 separate USB cables).

Master Code:

#include <SPI.h>

void setup (void) {
  Serial.begin(9600); //set baud rate

  pinMode(SS, OUTPUT);
  digitalWrite(SS, HIGH); // disable Slave Select
  SPI.begin ();
  SPI.setClockDivider(SPI_CLOCK_DIV32);//divide the clock
}

void loop (void) {
   char c;
   digitalWrite(SS, LOW); // enable Slave Select
   // send test string
   for (const char * p = "This is a TEST!\n" ; c = *p; p++) 
   {
      SPI.transfer (c);
      Serial.print(c);
   }
   digitalWrite(SS, HIGH); // disable Slave Select
   delay(2000);
}

Slave Code:

#include <avr/io.h>
#include <avr/interrupt.h>

void setup() {
    // ... Serial initialization and other setup ...
    Serial.begin(9600); //set baud rate

    // NOTE: https://ww1.microchip.com/downloads/aemDocuments/documents/MCU08/ApplicationNotes/ApplicationNotes/TB3215-Getting-Started-with-SPI-DS90003215.pdf
    
    //PORTMUX.TWISPIROUTEA &= ~PORTMUX_SPI00_bm;  // cleared by default -> nothing to do
    PORTMUX.TWISPIROUTEA |= PORTMUX_SPI01_bm;     // set Portmux bit SPI01 for alternative mapping of SPI pins

    // SPI in slave mode
    SPI0.CTRLA = SPI_DORD_bm | SPI_ENABLE_bm & (~SPI_MASTER_bm);

    // Set pin modes
    PORTE.DIR &= ~PIN0_bm;  // MOSI
    PORTE.DIR |= PIN1_bm;  // MISO
    PORTE.DIR &= ~PIN2_bm;  // SCK
    PORTE.DIR &= ~PIN3_bm;  // CS / SS

    // Interrupt setup
    sei();     // Enable global interrupts
    SPI0.INTCTRL = SPI_IE_bm;  // SPI Interrupt enable
    SPI0.INTFLAGS |= SPI_IF_bm;    // clear interruptflag - not cleared automatically

}

// SPI interrupt routine
ISR(SPI0_INT_vect) {
    Serial.print("ISR - Triggered!\n");

    SPI0.INTFLAGS |= SPI_IF_bm;    // clear interruptflag - not cleared automatically
}

void loop() {
  Serial.print("And a new loop!\n");
  delay(5000);

}

I'll format this post maybe a little bit better in future, but I think that will help some guys, who are searching for exactly such a "template".

BR

2

@spacefish: This is, I think, the solution to your issue you've raised in April 2020.
Link: Setting up Nano Every as SPI slave

3

Post an annotated schematic, I do not have the time to spend on a word salad.