dataframe/readme.md

Simple wrapper for DataFrame

Create formatted frame from basic types:

• uint8_t, int8_t => 1Byte
• uint16_t, int16_t => 2Bytes
• uint32_t, int32_t => 4Bytes
• float => 4Bytes

Support modes:

• Plain (TYPE_PLAIN): construct simple dataframe,
• Basic (TYPE_HEADER_CRC): construct dataframe with header byte as irst byte and CRC checksum as last byte.

Data are stored in Little Endian format.

Structure of data frame (TYPE_HEADER_CRC):

• data[0] - starting byte (0xCC)
• data[1] - length of frame: count of bytes in payload. The first 2 bytes is not included to overal length. Maximum length: 254 (0xFE)
• payload
• CRC8
  
  

Structure of data frame (TYPE_PLAIN):

• data[0] - length of frame: count of bytes in payload. The first bytee is not included to overal length. Maximum length: 254 (0xFE)
• payload

The library contans universal function:

• uint8_t crc8(uint8_t crc, uint8_t Size, uint8_t *Buffer);
  • crc - inital value for CRC computig. For new frame, use 0x0
  • Size - size of data Buffer
    

Basic usage

    void main(){
    uint8_t data[128];

    DataFrame packet(data_packet, sizeof(data_packet), TYPE_HEADER_CRC);

    packet.AddUint8(0xAB);
    packet.AddUint16(65874);
    packet.AddInt8(-45874);
    packet.AddUint32(0x12345678);
    packet.AddInt32(-0xA2345678);
    
    packet.AddFloat(0.265);
    packet.AddFloat(-3.1415);

    int data_length = packet.Commit();
    uint8_t* frame = packet.GetFrame();
    }

CRC8 Computation

• Generator polynome: 0x97 -> 0x197 = x^8 + x^7 + x^4 + x^2 + x^1 +1
• CRC is implemented as fast computation with prepared CrcTable. Algorithm complexity is O(n)