SPI Example with Arduino Uno and MKR WiFi 1010

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

• Arduino Uno R3
• Arduino MKR WiFi 1010

Circuit Diagram

Code (MKR WiFi 1010 - controller)

#include 

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)

#include 

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;    
    }
}

Wiring

The computer powers the Arduino Uno via USB, and the MKR is powered by 5V from the Uno.

Results

Once everything is connected, you should see some values displayed in the Serial Monitor from the Uno.

Well done!

Thank you for reading.