Arduino SPI Interrupt Conflict Causes Data Corruption

In this tutorial, you'll learn about Arduino SPI Interrupt Conflict Causes Data Corruption. We cover key concepts, practical examples, and best practices to help you understand and apply this topic effectively.

The Problem

SPI data is corrupted when an interrupt fires during an SPI Transaction.

Quick Fix

Wrong

SPI.transfer(data);  // Interrupt may fire during transfer

Data corruption if another SPI-using interrupt fires during transfer.

Right

#include <SPI.h>

const int csPin = 10;

void safeSPITransfer(byte* data, int len) {
  SPISettings settings(4000000, MSBFIRST, SPI_MODE0);
  SPI.beginTransaction(settings);
  noInterrupts();  // Disable interrupts during transaction
  
  digitalWrite(csPin, LOW);
  for (int i = 0; i < len; i++) {
    data[i] = SPI.transfer(data[i]);
  }
  digitalWrite(csPin, HIGH);
  
  interrupts();  // Re-enable
  SPI.endTransaction();
}

void setup() {
  Serial.begin(9600);
  SPI.begin();
  pinMode(csPin, OUTPUT);
  digitalWrite(csPin, HIGH);
}

void loop() {
  byte buf[] = {0x00, 0x01, 0x02};
  safeSPITransfer(buf, 3);
  Serial.println("SPI transfer complete");
  delay(100);
}

SPI transfer complete — data not corrupted.

Prevention

Disable interrupts around SPI transfers if other ISRs might use SPI. The SPI.beginTransaction()/endTransaction() pair helps but does not prevent interrupts. On AVR, noInterrupts() globally disables interrupts. For ESP32, use portMUX or taskENTER_CRITICAL() for SMP safety.

DodaTech engineers apply these same patterns across Doda Browser, DodaZIP, and Durga Antivirus Pro for production IoT reliability.

FAQ