Michael Shimniok / Mbed 2 deprecated DataBus

Code for autonomous rover for Sparkfun AVC. DataBus won 3rd in 2012 and the same code was used on Troubled Child, a 1986 Jeep Grand Wagoneer to win 1st in 2014.

Dependencies:   mbed Watchdog SDFileSystem DigoleSerialDisp

MAVlink/include/checksum.h@25:bb5356402687, 2018-11-30 (annotated)

Committer:
shimniok
Date:
Fri Nov 30 16:11:53 2018 +0000
Revision:
25:bb5356402687
Parent:
0:a6a169de725f 
Initial publish of revised version.

Who changed what in which revision?

UserRevisionLine numberNew contents of line
shimniok 0:a6a169de725f 1 #ifdef __cplusplus
shimniok 0:a6a169de725f 2 extern "C" {
shimniok 0:a6a169de725f 3 #endif
shimniok 0:a6a169de725f 4
shimniok 0:a6a169de725f 5 #ifndef _CHECKSUM_H_
shimniok 0:a6a169de725f 6 #define _CHECKSUM_H_
shimniok 0:a6a169de725f 7
shimniok 0:a6a169de725f 8 #include "inttypes.h"
shimniok 0:a6a169de725f 9
shimniok 0:a6a169de725f 10
shimniok 0:a6a169de725f 11 /**
shimniok 0:a6a169de725f 12 *
shimniok 0:a6a169de725f 13 * CALCULATE THE CHECKSUM
shimniok 0:a6a169de725f 14 *
shimniok 0:a6a169de725f 15 */
shimniok 0:a6a169de725f 16
shimniok 0:a6a169de725f 17 #define X25_INIT_CRC 0xffff
shimniok 0:a6a169de725f 18 #define X25_VALIDATE_CRC 0xf0b8
shimniok 0:a6a169de725f 19
shimniok 0:a6a169de725f 20 /**
shimniok 0:a6a169de725f 21 * @brief Accumulate the X.25 CRC by adding one char at a time.
shimniok 0:a6a169de725f 22 *
shimniok 0:a6a169de725f 23 * The checksum function adds the hash of one char at a time to the
shimniok 0:a6a169de725f 24 * 16 bit checksum (uint16_t).
shimniok 0:a6a169de725f 25 *
shimniok 0:a6a169de725f 26 * @param data new char to hash
shimniok 0:a6a169de725f 27 * @param crcAccum the already accumulated checksum
shimniok 0:a6a169de725f 28 **/
shimniok 0:a6a169de725f 29 static inline void crc_accumulate(uint8_t data, uint16_t *crcAccum)
shimniok 0:a6a169de725f 30 {
shimniok 0:a6a169de725f 31 /*Accumulate one byte of data into the CRC*/
shimniok 0:a6a169de725f 32 uint8_t tmp;
shimniok 0:a6a169de725f 33
shimniok 0:a6a169de725f 34 tmp=data ^ (uint8_t)(*crcAccum &0xff);
shimniok 0:a6a169de725f 35 tmp^= (tmp<<4);
shimniok 0:a6a169de725f 36 *crcAccum = (*crcAccum>>8) ^ (tmp<<8) ^ (tmp <<3) ^ (tmp>>4);
shimniok 0:a6a169de725f 37 }
shimniok 0:a6a169de725f 38
shimniok 0:a6a169de725f 39 /**
shimniok 0:a6a169de725f 40 * @brief Initiliaze the buffer for the X.25 CRC
shimniok 0:a6a169de725f 41 *
shimniok 0:a6a169de725f 42 * @param crcAccum the 16 bit X.25 CRC
shimniok 0:a6a169de725f 43 */
shimniok 0:a6a169de725f 44 static inline void crc_init(uint16_t* crcAccum)
shimniok 0:a6a169de725f 45 {
shimniok 0:a6a169de725f 46 *crcAccum = X25_INIT_CRC;
shimniok 0:a6a169de725f 47 }
shimniok 0:a6a169de725f 48
shimniok 0:a6a169de725f 49
shimniok 0:a6a169de725f 50 /**
shimniok 0:a6a169de725f 51 * @brief Calculates the X.25 checksum on a byte buffer
shimniok 0:a6a169de725f 52 *
shimniok 0:a6a169de725f 53 * @param pBuffer buffer containing the byte array to hash
shimniok 0:a6a169de725f 54 * @param length length of the byte array
shimniok 0:a6a169de725f 55 * @return the checksum over the buffer bytes
shimniok 0:a6a169de725f 56 **/
shimniok 0:a6a169de725f 57 static inline uint16_t crc_calculate(uint8_t* pBuffer, int length)
shimniok 0:a6a169de725f 58 {
shimniok 0:a6a169de725f 59
shimniok 0:a6a169de725f 60 // For a "message" of length bytes contained in the unsigned char array
shimniok 0:a6a169de725f 61 // pointed to by pBuffer, calculate the CRC
shimniok 0:a6a169de725f 62 // crcCalculate(unsigned char* pBuffer, int length, unsigned short* checkConst) < not needed
shimniok 0:a6a169de725f 63
shimniok 0:a6a169de725f 64 uint16_t crcTmp;
shimniok 0:a6a169de725f 65 //uint16_t tmp;
shimniok 0:a6a169de725f 66 uint8_t* pTmp;
shimniok 0:a6a169de725f 67 int i;
shimniok 0:a6a169de725f 68
shimniok 0:a6a169de725f 69 pTmp=pBuffer;
shimniok 0:a6a169de725f 70
shimniok 0:a6a169de725f 71
shimniok 0:a6a169de725f 72 /* init crcTmp */
shimniok 0:a6a169de725f 73 crc_init(&crcTmp);
shimniok 0:a6a169de725f 74
shimniok 0:a6a169de725f 75 for (i = 0; i < length; i++){
shimniok 0:a6a169de725f 76 crc_accumulate(*pTmp++, &crcTmp);
shimniok 0:a6a169de725f 77 }
shimniok 0:a6a169de725f 78
shimniok 0:a6a169de725f 79 /* This is currently not needed, as only the checksum over payload should be computed
shimniok 0:a6a169de725f 80 tmp = crcTmp;
shimniok 0:a6a169de725f 81 crcAccumulate((unsigned char)(~crcTmp & 0xff),&tmp);
shimniok 0:a6a169de725f 82 crcAccumulate((unsigned char)((~crcTmp>>8)&0xff),&tmp);
shimniok 0:a6a169de725f 83 *checkConst = tmp;
shimniok 0:a6a169de725f 84 */
shimniok 0:a6a169de725f 85 return(crcTmp);
shimniok 0:a6a169de725f 86 }
shimniok 0:a6a169de725f 87
shimniok 0:a6a169de725f 88
shimniok 0:a6a169de725f 89
shimniok 0:a6a169de725f 90
shimniok 0:a6a169de725f 91 #endif /* _CHECKSUM_H_ */
shimniok 0:a6a169de725f 92
shimniok 0:a6a169de725f 93 #ifdef __cplusplus
shimniok 0:a6a169de725f 94 }
shimniok 0:a6a169de725f 95 #endif