simple-serial-port-server/serial.go

package main

import (
	"context"
	"errors"
	"fmt"
	zgpf_core "git.swzry.com/zry/zry-go-program-framework/core"
	"github.com/tarm/serial"
	"sync"
)

var _ zgpf_core.ISubService = (*SerialSubSvc)(nil)

type SerialSubSvc struct {
	serialCfg     *serial.Config
	serialPort    *serial.Port
	subSvcContext context.Context
	subSvcCancel  context.CancelFunc
	TxChan        chan []byte
	RxChan        chan []byte
}

func NewSerialSubSvc() *SerialSubSvc {
	s := &SerialSubSvc{
		TxChan: make(chan []byte),
		RxChan: make(chan []byte),
	}
	return s
}

func (s *SerialSubSvc) Prepare(ctx *zgpf_core.SubServiceContext) error {
	sd, ss, sp, err := GetDnSnP(Config.Serial.DataBits, Config.Serial.StopBits, Config.Serial.Parity)
	if err != nil {
		ctx.Error("invalid serial port config: ", err)
		return errors.New("invalid serial port config")
	}
	s.serialCfg = &serial.Config{
		Name:     Config.Serial.ComPort,
		Baud:     Config.Serial.Baudrate,
		Size:     sd,
		Parity:   sp,
		StopBits: ss,
	}
	return nil
}

func (s *SerialSubSvc) Run(ctx *zgpf_core.SubServiceContext) error {
	s.subSvcContext, s.subSvcCancel = context.WithCancel(ctx.GetParentContext())
	sport, err := serial.OpenPort(s.serialCfg)
	if err != nil {
		ctx.ErrorF("failed open serial port '%s': %v", s.serialCfg.Name, err)
		return errors.New("failed open serial port")
	}
	s.serialPort = sport
	ctx.InfoF("serial port '%s' opened", s.serialCfg.Name)
	defer s.serialPort.Close()
	wg := sync.WaitGroup{}
	wg.Add(2)
	go func() {
		defer wg.Done()
		readbuf := make([]byte, Config.Performance.RxBufferSize)
		for {
			n, xerr := s.serialPort.Read(readbuf)
			if xerr != nil {
				ctx.Error("error in read serial port: ", xerr)
				return
			}
			s.RxChan <- readbuf[:n]
		}
	}()
	go func() {
		defer wg.Done()
		for {
			select {
			case <-s.subSvcContext.Done():
				return
			case txdata := <-s.TxChan:
				_, xerr := s.serialPort.Write(txdata)
				if xerr != nil {
					ctx.Error("error in write serial port: ", xerr)
					return
				}
			}
		}
	}()
	wg.Wait()
	ctx.Info("serial sub service end.")
	return nil
}

func (s *SerialSubSvc) Stop(ctx *zgpf_core.SubServiceContext) {
	if s.subSvcCancel != nil {
		s.subSvcCancel()
	}
	if s.serialPort != nil {
		err := s.serialPort.Close()
		if err != nil {
			ctx.Warn("error in closing serial port: ", err)
		}
	}
}

func GetDnSnP(d int, s float32, p string) (byte, serial.StopBits, serial.Parity, error) {
	if d < 0 {
		return 0, 0, 0, fmt.Errorf("invalid databits: value %d is less than 0", d)
	}
	if d > 255 {
		return 0, 0, 0, fmt.Errorf("invalid databits: value %d is more than 255", d)
	}
	sd := byte(d)
	var ss serial.StopBits
	switch s {
	case 1:
		ss = serial.Stop1
		break
	case 1.5:
		ss = serial.Stop1Half
	case 2:
		ss = serial.Stop2
	default:
		return 0, 0, 0, fmt.Errorf("invalid stopbits:  %f (should be 1/1.5/2)", s)
	}
	var sp serial.Parity
	switch p {
	case "N":
		sp = serial.ParityNone
		break
	case "O":
		sp = serial.ParityOdd
		break
	case "E":
		sp = serial.ParityEven
		break
	case "M":
		sp = serial.ParityMark
		break
	case "S":
		sp = serial.ParitySpace
		break
	default:
		return 0, 0, 0, fmt.Errorf("invalid parity:  '%s' (should be N/O/E/M/S)", p)
	}
	return sd, ss, sp, nil
}