How to read negative numbers from arduino using visual basic.net

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I am trying to read numbers from Arduino using Visual Basic.net

I used SerialPort Tool and ReadByte function And I succeeded in reading the numbers from the Arduino

To understand me more This is an example

VB

TextBox1.Text = SerialPort1.ReadByte()

My code does this It reads numbers from Arduino using Visual Basic.net and writes them in a text box

But the ReadByte function only reads positive numbers and I want to read positive numbers and negative numbers

How can I read positive numbers and negative numbers from Arduino using Visual Basic.net ?

What I have tried:

I am trying to read numbers from Arduino using Visual Basic.net

I used SerialPort Tool and ReadByte function And I succeeded in reading the numbers from the Arduino

To understand me more This is an example

VB

TextBox1.Text = SerialPort1.ReadByte()

My code does this It reads numbers from Arduino using Visual Basic.net and writes them in a text box

But the ReadByte function only reads positive numbers and I want to read positive numbers and negative numbers

How can I read positive numbers and negative numbers from Arduino using Visual Basic.net ?

Posted 30-Sep-21 23:16pm

Member 15378285

Updated 30-Sep-21 23:30pm

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OriginalGriff · Answer 1 · 2021-09-30T23:30:00

Bytes are neither positive nor negative in themselves: they are a pure eight bit value and it's only when you convert them to an integer that they "Acquire" a sign (or strictly speaking any "numeric value" at all).
When you call ReadByte it returns a 32 bit integer which contains the byte value as it' least significant bits; all the others are zero, which means a positive value for an integer - a negative integer has the top bits set so a hex value of FFFFFFFF is minus one, FFFFFFFE is minus two, and so on.

If your Arduino is returning a byte value which uses the same scheme so FF is minus one, FE is minus two, ... then you will need to extend the "sign bit" through the rest of the integer value to get your "real number".

I'd probably do it by checking bit 7 of the integer, and using a binary OR to add FFFFFF00 to the value if it was set.