embassy 串口链路层实现

使用embassy在nrf52833上实现一个蓝牙网关功能。因为要跟主芯片通信，于是定义了link层通信协议：

构思了link层要实现的功能：

帧的解析封装都比较好实现：

///发送封装
pub fn pack_send_msg(
    func_code: FuncCode,
    msg_id: u16,
    msg: &[u8],
) -> Result<Vec<u8, MSG_DATA_LEN_MAX>, ComLinkError> {
    let mut buf = Vec::new();
    buf.push(0xA5)?; //frame head high byte
    buf.push(0x5A)?; //frame head low byte
    buf.push(func_code.into())?; //function code
    buf.extend_from_slice(&msg_id.to_be_bytes())?; //msg id
    buf.extend_from_slice(&(msg.len() as u16).to_be_bytes())?; //msg length
    buf.extend_from_slice(msg)?; //msg data
    let crc = crc16(0xffff, &buf[2..]);
    buf.extend_from_slice(&crc.to_be_bytes())?; //crc16
    Ok(buf)
}

pub struct MsgParser {
    state: ParseState, //parse state
    calc_crc: u16,     //calculated crc value
    msg: MsgRecv,      // msg storage when parsing
}

#[derive(Debug, Clone, Default)]
struct DataVec(Vec<u8, MSG_RECV_PARSE_BUF_LEN>);
impl Format for DataVec {
    fn format(&self, fmt: defmt::Formatter) {
        defmt::write!(fmt, "{:02x}", Bytes(&self.0))
    }
}

#[derive(Debug, Clone, Default, Format)]
pub struct MsgRecv {
    func_code: FuncCode,
    msg_id: u16,
    msg_len: u16,
    data: DataVec,
    recv_crc: u16, //received crc value
}
///接收解析
    pub fn parse(&mut self, data: &[u8]) -> MsgRecvVec {
        let mut msg_recv_vec = MsgRecvVec::default();
        let mut i = 0;

        while i < data.len() {
            match self.state {
                ParseState::BeginH => {
                    if data[i] == 0xA5 {
                        self.state = ParseState::BeginL;
                    }
                    i += 1;
                }
                ParseState::BeginL => {
                    if data[i] == 0x5A {
                        self.state = ParseState::FuncCode;
                    } else