30 May 2023 2 min read Embedded Systems

SPI Example with Arduino Uno and MKR WiFi 1010

Arduino Uno and MKR WiFi 1010 connected through SPI.

This is an older post from when this site covered general embedded learning. The site now focuses on modernising classic vehicles.

In this article, we'll review an example of communicating between an Arduino Uno and an Arduino MKR WiFi 1010 using the SPI protocol.

We'll create some values on the MRK side and send them to the Uno. Once the Uno receives the values, it will print them out on the Serial Monitor.

Required Components

Circuit Diagram

Arduino Uno powers the MKR WiFi 1010. The Uno receives SPI signals from the MKR and displays them on the Monitor.

Code (MKR WiFi 1010 - controller)

Click to see some code.

#include <SPI.h>

volatile uint8_t m=0;

char myCmd[5] = {'p', 's', 'l', 'r', '3'};


void setup (void)
{
    pinMode(MOSI, OUTPUT);
    pinMode(MISO, INPUT);
    pinMode(SCK, OUTPUT);
    pinMode(SS, OUTPUT); 
    Serial.begin(115200);
    Serial.println();
 
    digitalWrite(SS, HIGH);
 
    SPI.begin();   
}   
     
void loop (void)
{
    for(byte i = 0; i < sizeof(myCmd); i++) { 
        m = (uint8_t)myCmd[i];
        digitalWrite(SS, LOW);
        SPI.transfer(m);
        digitalWrite(SS, HIGH);
        Serial.print("data sent: "); Serial.println(m);
        delay(2000);
    }
}

Code (Uno - peripheral)

Click to see some code.

#include <SPI.h>

volatile byte c = 0;
volatile boolean process_it = false;

void setup (void)
{
    pinMode(MOSI, INPUT);
    pinMode(SCK, INPUT);
    pinMode(SS, INPUT);
    pinMode(MISO, OUTPUT);

    // turn on SPI in peripheral mode
    SPCR |= _BV(SPE);
    Serial.begin(115200);

    SPI.attachInterrupt();         
}

// SPI interrupt routine
ISR (SPI_STC_vect)
{      
    c = SPDR;
    process_it = true;
}  // end of interrupt service routine (ISR) SPI_STC_vect

void loop (void){
    if (process_it) {
        Serial.print("data received: ");
        Serial.println((char)c);    
        process_it = false;    
    }
}