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definitions.md

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Data Types and other Definitions

Endianness

The Endianness for all data types is 'little-endian'. A little-endian system stores the least-significant byte first, at the smallest address.

Preferred Standard Data Types

The following data types are used as far as possible.

Unsigned Integers       u8, u16, u32, u64
Signed Integers         i8, i16, i32, i64
Bool                    true, false         u8, true = 1, false = 0
Floating Point Numbers  f32, f64            f32::NAN [0, 0, 0xc0, 0x7f]
                                            f64::NAN [0, 0, 0, 0, 0, 0, 0xf8, 0x7f]
Byte Arrays             u8[N]

Defined Data Types

HwVersion:
    Manufacturer    u8[0]  Enumeration
    Major           u8[1]     
    Minor           u8[2]  Hw with same major and minor is firmware compatible
    Patch           u8[3]    

FwVersion
    Major           u8[0]
    Minor           u8[1]     
    Patch           u8[2]
    Buildindex      u8[3]

Data Types for Special Cases

Unsigned Integers       u1, u2, u3, ... u64
Signed Integers         i1, i2, i3, ... i64

Cyclic redundancy check

If the specification refers to a CRC that is not specified in more detail, use this one:

Uses CRC-32 (Ethernet, STM32) polynomial: 0x4C11DB7
X32 + X26 + X23 + X22 + X16 + X 12 + X11 + X10 +X8 + X7 + X5 + X4 + X2+ X + 1

Calculation with Python:

def crc(data: bytes) -> int:
    crc=0xffffffff
    buf = bytearray()
    for b in data:
        buf.insert(0, b)
        if len(buf) == 4:
            for val in buf:
                crc ^= val << 24
                for _ in range(8):
                    crc = crc << 1 if (crc & 0x80000000) == 0 else (crc << 1) ^ 0x104c11db7
            buf = bytearray()
    return crc

Device Unique ID (UID)

The UID should be unique in the system so that the devices can be clearly distinguished. It is a 32-bit number that can be created, by generating a CRC using the controller-specific data.

Manufacturer and Hardware Versions

Manufacturer

1       Larus
2       Air Avionics


Hardware Releases

Manufacturer    Name of Device      HwVersion
---------------------------------------------
Larus           Sensorbox MK1, MK2  1.1.1.0
Larus           Audiobox            1.2.1.0
Larus           Frontend 57 V1      1.3.1.0
Larus           Frontend 57 V2      1.3.2.0
AirAvionics     AD57 v1             2.1.1.0
AirAvionics     Ad57 v2             2.1.2.0