[CRC] Added common CRC

src/RadioLib.h

@@ -110,6 +110,9 @@
 #include "protocols/Print/Print.h"
 #include "protocols/BellModem/BellModem.h"
 
+// utilities
+#include "utils/CRC.h"
+
 // only create Radio class when using RadioShield
 #if defined(RADIOLIB_RADIOSHIELD)
 

src/utils/CRC.cpp

@@ -0,0 +1,39 @@
+#include "CRC.h"
+
+RadioLibCRC::RadioLibCRC(uint8_t size, uint32_t poly, uint32_t init, uint32_t out, bool refIn, bool refOut) {
+  this->size = size;
+  this->poly = poly;
+  this->init = init;
+  this->out = out;
+  this->refIn = refIn;
+  this->refOut = refOut;
+}
+
+uint32_t RadioLibCRC::checksum(uint8_t* buff, size_t len) {
+  uint32_t crc = this->init;
+  for(size_t i = 0; i < len; i+=this->size/8) {
+    uint32_t window = 0;
+    for(uint8_t j = 0; j < this->size/8; j++) {
+      uint8_t inByte = buff[i + j];
+      if(this->refIn) {
+        inByte = Module::reflect(inByte, 8);
+      }
+      window |= (inByte << ((this->size - 8) - 8*j));
+    }
+    crc ^= window;
+    for(size_t k = 0; k < this->size; k++) {
+      if(crc & ((uint32_t)1 << (this->size - 1))) {
+        crc <<= (uint32_t)1;
+        crc ^= this->poly;
+      } else {
+        crc <<= (uint32_t)1;
+      }
+    }
+  }
+  crc ^= this->out;
+  if(this->refOut) {
+    crc = Module::reflect(crc, this->size);
+  }
+  crc &= (uint32_t)0xFFFFFFFF >> (32 - this->size);
+  return(crc);
+}

src/utils/CRC.h

@@ -0,0 +1,71 @@
+#if !defined(_RADIOLIB_CRC_H)
+#define _RADIOLIB_CRC_H
+
+#include "../TypeDef.h"
+#include "../Module.h"
+#if defined(RADIOLIB_BUILD_ARDUINO)
+#include "../ArduinoHal.h"
+#endif
+
+// CCITT CRC properties (used by AX.25)
+#define RADIOLIB_CRC_CCITT_POLY                                 (0x1021)
+#define RADIOLIB_CRC_CCITT_INIT                                 (0xFFFF)
+#define RADIOLIB_CRC_CCITT_OUT                                  (0xFFFF)
+
+/*!
+  \class AX25Frame
+  \brief Abstraction of AX.25 frame format.
+*/
+class RadioLibCRC {
+  public:
+    /*!
+      \brief CRC size in bits.
+    */
+    uint8_t size;
+
+    /*!
+      \brief CRC polynomial.
+    */
+    uint32_t poly;
+
+    /*!
+      \brief Initial value.
+    */
+    uint32_t init;
+
+    /*!
+      \brief Final XOR value.
+    */
+    uint32_t out;
+
+    /*!
+      \brief Whether to reflect input bytes.
+    */
+    bool refIn;
+
+    /*!
+      \brief Whether to reflect the result.
+    */
+    bool refOut;
+
+    /*!
+      \brief Default constructor.
+      \param size CRC size in bits.
+      \param poly CRC polynomial.
+      \param init Initial value.
+      \param out Final XOR value.
+      \param refIn Whether to reflect input bytes.
+      \param refOut Whether to reflect the result.
+    */
+    RadioLibCRC(uint8_t size, uint32_t poly, uint32_t init, uint32_t out, bool refIn, bool refOut);
+
+    /*!
+      \brief Calcualte checksum of a buffer.
+      \param buff Buffer to calculate the checksum over.
+      \param len Size of the buffer in bytes.
+      \returns The resulting checksum.
+    */
+    uint32_t checksum(uint8_t* buff, size_t len);
+};
+
+#endif