Code for autonomous ground vehicle, Data Bus, 3rd place winner in 2012 Sparkfun AVC.
Dependencies: Watchdog mbed Schedule SimpleFilter LSM303DLM PinDetect DebounceIn Servo
MAVlink/include/checksum.h@0:826c6171fc1b, 2012-06-20 (annotated)
- Committer:
- shimniok
- Date:
- Wed Jun 20 14:57:48 2012 +0000
- Revision:
- 0:826c6171fc1b
Updated documentation
Who changed what in which revision?
User | Revision | Line number | New contents of line |
---|---|---|---|
shimniok | 0:826c6171fc1b | 1 | #ifdef __cplusplus |
shimniok | 0:826c6171fc1b | 2 | extern "C" { |
shimniok | 0:826c6171fc1b | 3 | #endif |
shimniok | 0:826c6171fc1b | 4 | |
shimniok | 0:826c6171fc1b | 5 | #ifndef _CHECKSUM_H_ |
shimniok | 0:826c6171fc1b | 6 | #define _CHECKSUM_H_ |
shimniok | 0:826c6171fc1b | 7 | |
shimniok | 0:826c6171fc1b | 8 | #include "inttypes.h" |
shimniok | 0:826c6171fc1b | 9 | |
shimniok | 0:826c6171fc1b | 10 | |
shimniok | 0:826c6171fc1b | 11 | /** |
shimniok | 0:826c6171fc1b | 12 | * |
shimniok | 0:826c6171fc1b | 13 | * CALCULATE THE CHECKSUM |
shimniok | 0:826c6171fc1b | 14 | * |
shimniok | 0:826c6171fc1b | 15 | */ |
shimniok | 0:826c6171fc1b | 16 | |
shimniok | 0:826c6171fc1b | 17 | #define X25_INIT_CRC 0xffff |
shimniok | 0:826c6171fc1b | 18 | #define X25_VALIDATE_CRC 0xf0b8 |
shimniok | 0:826c6171fc1b | 19 | |
shimniok | 0:826c6171fc1b | 20 | /** |
shimniok | 0:826c6171fc1b | 21 | * @brief Accumulate the X.25 CRC by adding one char at a time. |
shimniok | 0:826c6171fc1b | 22 | * |
shimniok | 0:826c6171fc1b | 23 | * The checksum function adds the hash of one char at a time to the |
shimniok | 0:826c6171fc1b | 24 | * 16 bit checksum (uint16_t). |
shimniok | 0:826c6171fc1b | 25 | * |
shimniok | 0:826c6171fc1b | 26 | * @param data new char to hash |
shimniok | 0:826c6171fc1b | 27 | * @param crcAccum the already accumulated checksum |
shimniok | 0:826c6171fc1b | 28 | **/ |
shimniok | 0:826c6171fc1b | 29 | static inline void crc_accumulate(uint8_t data, uint16_t *crcAccum) |
shimniok | 0:826c6171fc1b | 30 | { |
shimniok | 0:826c6171fc1b | 31 | /*Accumulate one byte of data into the CRC*/ |
shimniok | 0:826c6171fc1b | 32 | uint8_t tmp; |
shimniok | 0:826c6171fc1b | 33 | |
shimniok | 0:826c6171fc1b | 34 | tmp=data ^ (uint8_t)(*crcAccum &0xff); |
shimniok | 0:826c6171fc1b | 35 | tmp^= (tmp<<4); |
shimniok | 0:826c6171fc1b | 36 | *crcAccum = (*crcAccum>>8) ^ (tmp<<8) ^ (tmp <<3) ^ (tmp>>4); |
shimniok | 0:826c6171fc1b | 37 | } |
shimniok | 0:826c6171fc1b | 38 | |
shimniok | 0:826c6171fc1b | 39 | /** |
shimniok | 0:826c6171fc1b | 40 | * @brief Initiliaze the buffer for the X.25 CRC |
shimniok | 0:826c6171fc1b | 41 | * |
shimniok | 0:826c6171fc1b | 42 | * @param crcAccum the 16 bit X.25 CRC |
shimniok | 0:826c6171fc1b | 43 | */ |
shimniok | 0:826c6171fc1b | 44 | static inline void crc_init(uint16_t* crcAccum) |
shimniok | 0:826c6171fc1b | 45 | { |
shimniok | 0:826c6171fc1b | 46 | *crcAccum = X25_INIT_CRC; |
shimniok | 0:826c6171fc1b | 47 | } |
shimniok | 0:826c6171fc1b | 48 | |
shimniok | 0:826c6171fc1b | 49 | |
shimniok | 0:826c6171fc1b | 50 | /** |
shimniok | 0:826c6171fc1b | 51 | * @brief Calculates the X.25 checksum on a byte buffer |
shimniok | 0:826c6171fc1b | 52 | * |
shimniok | 0:826c6171fc1b | 53 | * @param pBuffer buffer containing the byte array to hash |
shimniok | 0:826c6171fc1b | 54 | * @param length length of the byte array |
shimniok | 0:826c6171fc1b | 55 | * @return the checksum over the buffer bytes |
shimniok | 0:826c6171fc1b | 56 | **/ |
shimniok | 0:826c6171fc1b | 57 | static inline uint16_t crc_calculate(uint8_t* pBuffer, int length) |
shimniok | 0:826c6171fc1b | 58 | { |
shimniok | 0:826c6171fc1b | 59 | |
shimniok | 0:826c6171fc1b | 60 | // For a "message" of length bytes contained in the unsigned char array |
shimniok | 0:826c6171fc1b | 61 | // pointed to by pBuffer, calculate the CRC |
shimniok | 0:826c6171fc1b | 62 | // crcCalculate(unsigned char* pBuffer, int length, unsigned short* checkConst) < not needed |
shimniok | 0:826c6171fc1b | 63 | |
shimniok | 0:826c6171fc1b | 64 | uint16_t crcTmp; |
shimniok | 0:826c6171fc1b | 65 | //uint16_t tmp; |
shimniok | 0:826c6171fc1b | 66 | uint8_t* pTmp; |
shimniok | 0:826c6171fc1b | 67 | int i; |
shimniok | 0:826c6171fc1b | 68 | |
shimniok | 0:826c6171fc1b | 69 | pTmp=pBuffer; |
shimniok | 0:826c6171fc1b | 70 | |
shimniok | 0:826c6171fc1b | 71 | |
shimniok | 0:826c6171fc1b | 72 | /* init crcTmp */ |
shimniok | 0:826c6171fc1b | 73 | crc_init(&crcTmp); |
shimniok | 0:826c6171fc1b | 74 | |
shimniok | 0:826c6171fc1b | 75 | for (i = 0; i < length; i++){ |
shimniok | 0:826c6171fc1b | 76 | crc_accumulate(*pTmp++, &crcTmp); |
shimniok | 0:826c6171fc1b | 77 | } |
shimniok | 0:826c6171fc1b | 78 | |
shimniok | 0:826c6171fc1b | 79 | /* This is currently not needed, as only the checksum over payload should be computed |
shimniok | 0:826c6171fc1b | 80 | tmp = crcTmp; |
shimniok | 0:826c6171fc1b | 81 | crcAccumulate((unsigned char)(~crcTmp & 0xff),&tmp); |
shimniok | 0:826c6171fc1b | 82 | crcAccumulate((unsigned char)((~crcTmp>>8)&0xff),&tmp); |
shimniok | 0:826c6171fc1b | 83 | *checkConst = tmp; |
shimniok | 0:826c6171fc1b | 84 | */ |
shimniok | 0:826c6171fc1b | 85 | return(crcTmp); |
shimniok | 0:826c6171fc1b | 86 | } |
shimniok | 0:826c6171fc1b | 87 | |
shimniok | 0:826c6171fc1b | 88 | |
shimniok | 0:826c6171fc1b | 89 | |
shimniok | 0:826c6171fc1b | 90 | |
shimniok | 0:826c6171fc1b | 91 | #endif /* _CHECKSUM_H_ */ |
shimniok | 0:826c6171fc1b | 92 | |
shimniok | 0:826c6171fc1b | 93 | #ifdef __cplusplus |
shimniok | 0:826c6171fc1b | 94 | } |
shimniok | 0:826c6171fc1b | 95 | #endif |