The story of DBC (ii)

The previous article describes the MSB and LSB, which describes more complex: signed and unsigned numbers.

1. Signal Symbols

The can signal has its physical significance, such as temperature, torque, etc., these signals are negative, there are 2 common solutions:

1) Set offset to negative value

If the temperature offset=-40, the temperature minimum-40.

2) can signal type is set to signed

As mentioned in the previous article, the signal definition has signedflag, when Signedflag is the minus sign, the signal is represented by the symbol.

• Format: Sg_ Name : StartBit | Length @ byteorder signedflag (Factor,Offset) [Minimum | Maximum] "Unit" Receiver1,Receiver2

2. signal Transmission

The comparison length is a byte (8 bit) data transfer.

1) Unsigned number

Value range: 0~255 (2^8-1), transfer the original code. For example: 7=00000111.

2) signed number

The highest bit is the sign bit, the value range: -128~127, positive transmission of the original code, negative transmission complement. For example-7, the original code = 10000111, complement (except the sign bit counter, plus 1) = 11111001. The network transmits is the complement.

3. Signal Parsing

Based on the previous article, the Dbcvalue project was updated to compare the values of unsigned data. Reply to "dbc example" to get.

1) Unsigned number

2) signed number

The story of DBC (ii)