Question

I need to be able to write signed bytes to a serial port using

SerialPort.Write() method, except that method only takes byte[] arrays of unsigned bytes, how would i write a signed byte to the serial port?

For what I’m working on the particular command takes values from -1700 to 1700.

thanks

nightmares

Answer 1

The serial communication channel has no concept of signed or unsigned, only a concept of 1’s and 0’s on the wire. It is your operating system (and ultimately your CPU architecture) that assigns a numeric value to those 1’s and 0’s, on both the sending and receiving side.

The value range you state cannot be represented in a byte (per my comment and your reply). You need to understand what bit pattern the receiving device expects for a given number (is the other device big endian or little endian?), and then you can send an appropriate sequence of byte[] to represent the number you want to transmit.

If both devices have the same endianness, you can setup an array of short then copy to an array of byte like this:

short[] sdata = new short[] { 1, -1 };
byte[] bdata = new byte[sdata.Length * 2];

Buffer.BlockCopy(sdata, 0, bdata, 0, bdata.Length);

However, be sure and test for a range of values. Especially if you are dealing with embedded devices, numeric encoding may not be exactly as on an Intel PC.