Reading from serial port with while-loop

Question

I’ve written a short program in Go to communicate with a sensor through a serial port: ``` package main import ( "fmt" "github.com/tarm/goserial" "time" ) func main() { c := &serial.Config{Name: "/dev/ttyUSB0", Baud: 9600} s, err := serial.OpenPort(c) if err != nil { fmt.Println(err) } _, err = s.Write([]byte("\x16\x02N0C0 G A\x03\x0d\x0a")) if err != nil { fmt.Println(err) } time.Sleep(time.Second/2) buf := make([]byte, 40) n, err := s.Read(buf) if err != nil { fmt.Println(err) } fmt.Println(string(buf[:n])) s.Close() } ``` It works fine, but after writing to the port I have to wait about half a second before I can start reading from it. I would like to use a while-loop instead of `time.Sleep` to read all incoming data. My attempt doesn’t work: ``` buf := make([]byte, 40) n := 0 for { n, _ := s.Read(buf) if n > 0 { break } } fmt.Println(string(buf[:n])) ``` I guess `buf` gets overwritten after every loop pass. Any suggestions?

Accepted Answer

Your problem is that `Read()` will return whenever it has some data - it won't wait for all the data. See the io.Reader specification for more info

What you want to do is read until you reach some delimiter. I don't know exactly what format you are trying to use, but it looks like maybe `\x0a` is the end delimiter.

In which case you would use a bufio.Reader like this

```
reader := bufio.NewReader(s)
reply, err := reader.ReadBytes('\x0a')
if err != nil {
    panic(err)
}
fmt.Println(reply)
```

Which will read data until the first `\x0a`.

Reading from serial port with while-loop

Solution

Problem