I want to make a Rust program to communicate with a arduino uno having the following code to to echo each byte:

void setup() {
  Serial.begin(112500);
}
void loop() {
  if (Serial.available()) {
    int inByte = Serial.read();
    Serial.write(inByte);
  }
}

With the following Rust code:

use std::{thread::sleep, time::Duration};
use serial2::SerialPort;

// Entry point
fn main() {
    let ps = SerialPort::available_ports()
        .unwrap()
        .into_iter()
        .filter(|x| x.to_string_lossy().starts_with("/dev/ttyUSB"))
        .collect::<Vec<_>>();
    let pth = ps[0].clone();
    let sp = SerialPort::open(pth, 115200).unwrap();
    sleep(Duration::from_millis(3000));
    let _ = sp.discard_input_buffer();
    let data=b"asdfg";
    let _m = sp.write(data).unwrap();
    let _ = sp.flush();
    println!("Sending : {:?}", data);
    let mut buf: Vec<u8> = vec![0; 5];
    let _ = sp.read(&mut buf);
    println!("Got : {:?}", buf);
}

Here is the output of the code:

Sending : [97, 115, 100, 102, 103]
Got : [97, 46, 150, 157, 0]

And here is the problem, the bytes sent and received are not the same. As of my experimentation the problem lies with the writing to serial port part. serialport crate also had the same issue. I tried with resberry pi pico had the same issue.

I have coded the same thing in julia it works as expected.

julia> using LibSerialPort

julia> s=LibSerialPort.open("/dev/ttyUSB0", 112500)
SerialPort(Ptr{LibSerialPort.Lib.SPPort} @0x0000000001bb9fe0, false, true, 0x00000000, 0x00000000)

julia> str="asdfg"
"asdfg"

julia> bytes = collect(codeunits(str))
5-element Vector{UInt8}:
 0x61
 0x73
 0x64
 0x66
 0x67

julia> sleep(3)

julia> write(s, bytes)
5

julia> sleep(1)

julia> rd=read(s)
5-element Vector{UInt8}:
 0x61
 0x73
 0x64
 0x66
 0x67

julia> rd==bytes
true

I am using Linux mint 22.