AT commands exchange with /dev/tty* - linux

Question

I have a device with a GPRS onboard. GPRS connects with the third-party application and it works. I need to know the signal strength of the connection, so, I use ATZ, then AT+CSQ commands. When I work using some terminal software it works. Then, I had tried to use https://github.com/ishuah/bifrost soft as a terminal. It works as well. But how can I simply communicate with a device, not using terminal, without re-connection or connection abortion, etc?
I tried simply echo ATZ > /dev/ttyX - no answer
// This writes, but reads only zeros (((
package main
import (
"github.com/jacobsa/go-serial/serial"
"io"
"log"
"time"
"fmt"
)
func Sleep(duration int) {
time.Sleep(time.Second * time.Duration(duration))
}
func printBuf(b []byte){
for _, val:=range b {
fmt.Printf("%x ", val)
}
}
func main(){
options := serial.OpenOptions{
PortName: "/dev/ttyX",
BaudRate: 115200,
DataBits: 8,
StopBits: 1,
MinimumReadSize: 0,
InterCharacterTimeout: 50,
}
port, err := serial.Open(options)
if err != nil {
log.Printf("port.Read: %v", err)
return
}
// Make sure to close it later.
defer port.Close()
var s string = `AT+CSQ`
b:=[]byte(s)
n, err := port.Write(b)
if err != nil {
log.Printf("port.Write: %v", err)
}
log.Println("Written bytes: ", n)
//Sleep(1)
res := make([]byte, 64)
n, err = port.Read(res)
if err != nil && err != io.EOF {
log.Printf("port.Read: %v", err)
}
log.Println("READ bytes: ", n)
printBuf(res)
}
/*
I expect (for example):
---------
ATZ
OK
AT+CSQ
+CSQ 22.4
*/

Answer 1

Most serial devices need a termination character to react to the commands they receive.
If you add it, your code should work:
var s string = `AT+CSQ\r`
I don't see any other differences from your code and sending a command using a serial terminal. The same should apply when you echo the command directly onto the port file descriptor.