C# 帮助将两个字节字拆分成字节

Question

Hello I am relatively new to C# programming and would appreciate some help, I am writing a program that communicates with a machine via RS232 and need to send a series of bytes to initiate coms. I have a two byte 16bit CRC word at the end of the packet that I think I need to split up into two bytes to fit into an array of bytes

// { <DLE> , <STX> , "G" , <DLE> , <ETX> , 16 BIT CRC CCITT split into two bytes}

byte[] byteToSend = new byte[] { 0x10, 0x02, 0x47, 0x10, 0x03, 0x421F };

When I convert 0x421F into binary and split it in half I get 0x42 and 0x1F however the problem with the less significant byte 0x1F is when it is sent it is not padded with enough zeroes. I think it is just sent as <11111> instead of <00011111> as is required.

Any help would be MUCH appreciated THanks:)

Answer 1

byte[] byteToSend = new byte[] { 0x10, 0x02, 0x47, 0x10, 0x03, 0x1F, 0x42 }
                                                               -----^

Or use BitConverter (which understands endianness):

var bytes = BitConverter.GetBytes(0x421F);

Answer 2

byte[] byteToSend = new byte[] { 0x10, 0x02, 0x47, 0x10, 0x03, 0x1F, 0x42 }
                                                               -----^

You need the bytes flipped if the target machine wants little-endian (likely if it's eg x86). If it's big-endian, use

byte[] byteToSend = new byte[] { 0x10, 0x02, 0x47, 0x10, 0x03, 0x42, 0x1F }
                                                               -----^

as Robert Harvey wrote.

(If you're not sure of the endianness, just try both.)

Answer 3

Is this right?

        ushort value = 0x421F;
        byte value1 = (byte)(0x421F & 0xFF);
        byte value2 = (byte)(0x421F >> 8);