Optimized CRC32 library for Arduino

This is a target independent, flash and RAM size optimized CRC32 library for Arduino without CRC tables.

Library features

• Compatible with standard CRC32 algorithms
• Small flash footprint
• No RAM buffer allocations
• 32-bit table-less CRC32 calculation on:
  • Arduino String object
  • Single null-terminated character array
  • Single buffer
  • Multiple null-terminated character arrays
  • Multiple buffers
• No buffer alignment needed
• Buffer input length in Bytes
• Big and little endian input buffers
• Arduino C library, compatible with C and C++ applications
• CRC32 polynomial: 0xEDB88320

Hardware

This library can be used on any 8 or 32-bit target and is optimized for small flash/RAM footprints without CRC table allocations in RAM.

Examples and benchmarks

Arduino IDE | Examples | Erriez CRC32:

• ErriezCRC32
• ErriezCRC32Benchmark

Benchmark results on buffers

The benchmark results below may be different for each target and run. Lower duration means faster CRC calculation.

Board	F_CPU	4 Bytes	64 Bytes	512 Bytes	1024 Bytes
Arduino UNO (ATMega328)	16MHz	80us	1172us	9000us	17112us
ESP8266 (WeMOS D1 R2)	160MHz	3us	35us	279us	557us
ESP32 (WeMOS Lolin32)	80MHz	2us	15us	111us	223us
DUE (SAM3X8E ARM Cortex-M3)	84MHz	6us	70us	547us	1103us

Benchmarks performed with the following versions:

• Arduino IDE v1.8.5
• Arduino AVR Boards v1.6.21 (Arduino UNO)
• esp8266 v2.4.2
• Arduino SAM Boards (32-bits ARM Cortex-M3) v1.6.11

Unit tests

This library contains extensive unit tests on a various number of buffer types and lengths:

• ErriezCRC32UnitTest

Library documentation

• Doxygen online HTML
• Doxygen PDF

Usage

Introduction

The library consists of four C-functions for CRC calculation:

// Calculate CRC32 on null-terminated character array (string)
uint32_t crc32String(const char *buffer);
// Calculate CRC32 on one single buffer
uint32_t crc32Buffer(const void *buffer, size_t bufferLength);

// Calculate CRC32 on multiple buffers
// First crc32Update() call should start with argument crc = CRC32_INITIAL
// Next crc32Update() calls should set argument crc = previousCRC
uint32_t crc32Update(const void *buffer, size_t bufferLength, uint32_t crc);
// Call crc32Update() at the end after the last crc32Update()
uint32_t crc32Final(uint32_t crc);

Initialization

Only an include file is required. No object allocation or library initialization required.

#include <ErriezCRC32.h>

Calculate CRC32 on Arduino String

String msg = "Hello world String!";
uint32_t crc = crc32String(msg.c_str());

Calculate CRC32 on null-terminated character array

char msg[] = "Hello world char array!";
uint32_t crc = crc32String(msg);

Calculate CRC32 on single character buffer

char msg[] = "Hello world single buffer!";
uint32_t crc = crc32Buffer(msg, strlen(msg));

Calculate CRC32 on multiple characters

uint32_t crc;

crc = crc32Update("Hello ", 6, CRC32_INITIAL);
crc = crc32Update("world ", 6, crc);
crc = crc32Update("multiple ", 9, crc);
crc = crc32Update("buffers!", 8, crc);
crc = crc32Final(crc);

Calculate CRC32 on multiple buffers

const uint8_t testBuffer1[3] = { 0xEB, 0xE5, 0x51 };
const uint8_t testBuffer2[5] = { 0x87, 0x7F, 0xB8, 0x18, 0x4E };
uint32_t crc;

crc = crc32Update(testBuffer1, sizeof(testBuffer1), CRC32_INITIAL);
crc = crc32Update(testBuffer2, sizeof(testBuffer2), crc);
crc = crc32Final(crc);

Check CRC

void checkCRC(uint32_t crcCalculated, uint32_t crcExpected)
{
    printCRC(crcCalculated);
    Serial.print(F("..."));

    if (crcCalculated == crcExpected) {
        Serial.println(F("OK"));
    } else {
        Serial.print(F("FAILED! Expected: "));
        printCRC(crcExpected);
        Serial.println(F(""));
    }
}

Print 32-bit CRC value

Printing a uint32_t value is not implemented on some targets which is a limitation of Serial.print() or sprintf(). This is a workaround to print a 32-bit hex value:

void printCRC(uint32_t crc)
{
	Serial.print("0x");
    for (int8_t i = 3; i >= 0; i--) {
        uint8_t c = crc >> (i * 8);
        if (c < 0x10) {
            Serial.print("0");
        }
        Serial.print(c, HEX);
    }
}

CRC-calculation with Python

>>> import binascii
>>> hex(binascii.crc32(b'Hello world String!') & 0xffffffff)
'0x55df869b'

Library dependencies

• ErriezCRC32Benchmark.ino: ErriezTimestamp.h
• ErriezCRC32UnitTest.ino: ArduinoUnit.h

Library installation

Please refer to the Wiki page.

Other Arduino Libraries and Sketches from Erriez

• Erriez Libraries and Sketches