go - 无法通过串口解析 GPS 信息

Question

我使用了以下软件包:

从串行端口读取 ( go get go.bug.st/serial )

解析来自串行端口的传入消息 ( go get adrianmo/go-nmea )

主机 : Windows 10
转到版本: go 版本 go1.14.4 windows/amd64
根据文档，我编写了一个简单的代码，打开专用串行端口( COM4 )并从端口读取 NMEA 数据并尝试根据 go-nmea 解析数据。包裹
数据
来自 GPS 传感器的传入数据:

$GPRMC,135533.000,A,5306.6644,N,00851.3177,E,0.11,214.59,300620,,,A*6E

$GPRMC,135534.000,A,5306.6643,N,00851.3177,E,0.06,187.72,300620,,,A*68

$GPRMC,135535.000,A,5306.6643,N,00851.3177,E,0.22,341.68,300620,,,A*6C

$GPRMC,135536.000,A,5306.6644,N,00851.3176,E,0.20,324.35,300620,,,A*60

$GPRMC,135537.000,A,5306.6645,N,00851.3176,E,0.12,348.37,300620,,,A*69

代码片段

package main

import (
    "fmt"
    "log"

    "github.com/adrianmo/go-nmea"
    "go.bug.st/serial"
)

func main() {

    mode := &serial.Mode{
        BaudRate: 9600,
        Parity:   serial.NoParity,
        DataBits: 8,
        StopBits: serial.OneStopBit,
    }
    serPort, err := serial.Open("COM4", mode)
    if err != nil {
        log.Fatal(err)
    }

    defer serPort.Close()

    buff := make([]byte, 1024)

    for {
        n, err := serPort.Read(buff)
        if err != nil {
            log.Fatal(err)
            break
        }
        if n == 0 {
            fmt.Println("\nEOF")
            break
        }
        rawSentence := string(buff[:n])
        fmt.Print(rawSentence)
        s, err := nmea.Parse(rawSentence)
        if err != nil {
            log.Fatal(err)
        }
        if s.DataType() == nmea.TypeRMC {
            m := s.(nmea.RMC)
            fmt.Printf("Raw sentence: %v\n", m)
            fmt.Printf("Time: %s\n", m.Time)
            fmt.Printf("Validity: %s\n", m.Validity)
            fmt.Printf("Latitude GPS: %s\n", nmea.FormatGPS(m.Latitude))
            fmt.Printf("Latitude DMS: %s\n", nmea.FormatDMS(m.Latitude))
            fmt.Printf("Longitude GPS: %s\n", nmea.FormatGPS(m.Longitude))
            fmt.Printf("Longitude DMS: %s\n", nmea.FormatDMS(m.Longitude))
            fmt.Printf("Speed: %f\n", m.Speed)
            fmt.Printf("Course: %f\n", m.Course)
            fmt.Printf("Date: %s\n", m.Date)
            fmt.Printf("Variation: %f\n", m.Variation)
        }
    }
}

问题
如果我运行代码，我会收到以下错误:

2020/06/30 16:02:16 nmea: sentence does not start with a '$' or '!'
exit status 1

这很奇怪，因为如果我注释掉代码解析代码:

        // s, err := nmea.Parse(rawSentence)
        // if err != nil {
        //  log.Fatal(err)
        // }
        // if s.DataType() == nmea.TypeRMC {
        //  m := s.(nmea.RMC)
        //  fmt.Printf("Raw sentence: %v\n", m)
        //  fmt.Printf("Time: %s\n", m.Time)
        //  fmt.Printf("Validity: %s\n", m.Validity)
        //  fmt.Printf("Latitude GPS: %s\n", nmea.FormatGPS(m.Latitude))
        //  fmt.Printf("Latitude DMS: %s\n", nmea.FormatDMS(m.Latitude))
        //  fmt.Printf("Longitude GPS: %s\n", nmea.FormatGPS(m.Longitude))
        //  fmt.Printf("Longitude DMS: %s\n", nmea.FormatDMS(m.Longitude))
        //  fmt.Printf("Speed: %f\n", m.Speed)
        //  fmt.Printf("Course: %f\n", m.Course)
        //  fmt.Printf("Date: %s\n", m.Date)
        //  fmt.Printf("Variation: %f\n", m.Variation)
        // }

如上所述，串行端口打印 GPS 坐标。
我哪里出错了？我尝试通过在代码中执行以下操作来删除换行符和回车符:

        rawSentence := string(buff[:n])
        rawSentence = string.ReplaceAll(rawSentence, "\r\n", "")
        fmt.Print(rawSentence)

但我仍然得到同样的错误。

Answer 1

我能够找出问题所在。我首先检查我的字节是如何从以下代码中读取的:

     n, err := serPort.Read(buff)
     fmt.Printf("%d", n)

它依次给出值 1和 73 , 74 .假设 1是设备本身发送的换行符，我发现这可能是代码无法捕获 $GPRMC的原因.
因此我修改了我的代码以检查读取的字节数是否总是大于 1 个字节

    for {
        n, err := serPort.Read(buff)
        fmt.Printf("%v\n", n)
        if err != nil {
            log.Fatal(err)
            break
        }
        // do not try to parse a single read byte
        // instead parse the actual incoming string.
        if n > 1 {
            rawSentence := string(buff[:n])
            fmt.Print(rawSentence)
            s, err := nmea.Parse(rawSentence)
            if err != nil {
                log.Fatal(err)
            }
            if s.DataType() == nmea.TypeRMC {
                m := s.(nmea.RMC)
                fmt.Printf("Raw sentence: %v\n", m)
                fmt.Printf("Time: %s\n", m.Time)
                fmt.Printf("Validity: %s\n", m.Validity)
                fmt.Printf("Latitude GPS: %s\n", nmea.FormatGPS(m.Latitude))
                fmt.Printf("Latitude DMS: %s\n", nmea.FormatDMS(m.Latitude))
                fmt.Printf("Longitude GPS: %s\n", nmea.FormatGPS(m.Longitude))
                fmt.Printf("Longitude DMS: %s\n", nmea.FormatDMS(m.Longitude))
                fmt.Printf("Speed: %f\n", m.Speed)
                fmt.Printf("Course: %f\n", m.Course)
                fmt.Printf("Date: %s\n", m.Date)
                fmt.Printf("Variation: %f\n", m.Variation)
            }
        }
    }

果然，代码现在可以工作了，导出的输出正是我所期望的:

$GPRMC,142312.000,A,5306.6774,N,00851.3114,E,0.04,14.48,300620,,,A*5A
Raw sentence: $GPRMC,142312.000,A,5306.6774,N,00851.3114,E,0.04,14.48,300620,,,A*5A
Time: 14:23:12.0000
Validity: A
Latitude GPS: 5306.6774
Latitude DMS: 53° 6' 40.644000"
Longitude GPS: 851.3114
Longitude DMS: 8° 51' 18.684000"
Speed: 0.040000
Course: 14.480000
Date: 30/06/20
Variation: 0.000000