Documentation of SerialPort Write says that
By default, SerialPort uses ASCIIEncoding to encode the characters. ASCIIEncoding encodes all characters greater than 127 as (char)63 or '?'. To support additional characters in that range, set Encoding to UTF8Encoding, UTF32Encoding, or UnicodeEncoding.
Also see here. Does this mean I can't send byte array using write?
By default, SerialPort uses ASCIIEncoding to encode the characters
You're confusing methods, which read/write strings or chars, with methods, which read/write bytes.
E.g., when you'll call this:
port.Write("абв")
you'll get "???" (0x3F 0x3F 0x3F) in the port buffer by default. On the other hand, this call:
// this is equivalent of sending "абв" in Windows-1251 encoding
port.Write(new byte[] { 0xE0, 0xE1, 0xE2 }, 0, 3)
will write sequence 0xE0 0xE1 0xE2 directly, without replacing bytes to 0x3F value.
UPD.
Let's look into source code:
public void Write(string text)
{
// preconditions checks are omitted
byte[] bytes = this.encoding.GetBytes(text);
this.internalSerialStream.Write(bytes, 0, bytes.Length, this.writeTimeout);
}
public void Write(byte[] buffer, int offset, int count)
{
// preconditions checks are omitted
this.internalSerialStream.Write(buffer, offset, count, this.writeTimeout);
}
Do you see the difference?
Method, that accepts string, converts strings to a byte array, using current encoding for port. Method, that accepts byte array, writes it directly to a stream, which is wrapper around native API.
And yes, documentation fools you.
This
port.Encoding = System.Text.Encoding.UTF8;
string testStr = "TEST";
port.Write(testStr);
and this
byte[] buf = System.Text.Encoding.UTF8.GetBytes(testStr);
port.Write(buf, 0, buf.Length);
will result in the same bytes being transmitted. In the latter one the Encoding of the serial port could be anything.
The serial port encoding only matters for methods that read or write strings.
