packets.rs: introduce CfgItfm frame

[gwbres]

Hello @lkolbly, @reitermarkus,

The CFG_ITFM frame is an important frame to our application, it controls the Interference (jamming) detection module.

I would like to control the Default value of this frame myself, as some part of the config words (Algorithm & config2) must have very specific (and undocumented values). This is how I did it

[maximeborges]

I think doing something similar to CfgPrtUart with UartMode would fit better in this code and be more Rustic.

Something along those lines:

#[ubx_packet_recv_send]
#[ubx(
    class = 0x06, 
    id = 0x39, 
    fixed_payload_len = 8,
    flags = "default_for_builder"
)]
struct CfgItfm {
    /// Interference config Word
    #[ubx(map_type = CfgItfmConfig)]
    config: u32,

    /// Extra settings
    #[ubx(map_type = CfgItfmConfig2)]
    config2: u32,
}

#[derive(Debug, Copy, Clone)]
#[cfg_attr(feature = "serde", derive(Serialize, Deserialize))]
pub struct CfgItfmConfig {
    /// Broadband jamming detection threshold (dB)
    bb_threshold: BbThreshold,
    /// CW jamming detection threshold (dB)
    cw_threshold: CwThreshold,
    /// Reserved algorithm settings - should be set to 0x16B156 in hex for correct settin
    algorithm_bits: AlgorithmBits,
    /// enable interference detection
    enable: bool,
}

#[derive(Debug, Clone, Copy)]
#[cfg_attr(feature = "serde", derive(Serialize, Deserialize))]
pub struct BbThreshold(u32);
impl BbThreshold {
    const POSITION: u32 = 0;
    const LENGTH: u32 = 4;
    const MASK: u32 = (1<<Self::LENGTH)-1;

    const fn into_raw(self) -> u32 {
        (self.0 & Self::MASK) << Self::POSITION
    }
}
impl From<u32> for BbThreshold {
    fn from(thres: u32) -> Self {
        Self(thres)
    }
}

And so on.

[gwbres]

I think doing something similar to CfgPrtUart with UartMode would fit better in this code and be more Rustic.

Yes that would work, I will update this PR accordingly

[gwbres]

Hello,

@maximeborges for information, the code did not compile as is, because every single structures involved in the ubx_recv/send generators require an into_raw() method.

I also wanted to keep the boolean native types for enable bits, because I think it's easier to use, at the user level.
Finally, I also wanted to use an enum not a struct wrapper for the AntennaSettings, to emphasize that only those values are correct. I use the [repr(u8)] derivation, and cast it to u32 in the needed into_raw() methods

[lkolbly]

This looks good to me, thank you!