byte conversion

[Rusty]

I am receiving tokens via TCP in byte arrays.
The first element within the byte array is a value of i.e. 253. When I receive the byte, it displays as -2 within the array.
Is this a sign bit issue? If this is correct, how do I convert the byte to a value of 253? (i.e. byteconverter.bytestoint(?) or ???)
thanks in advance

 

[Erel]

Basic4android type system is based on Java type system. In this type system there is only a signed byte. Which means that a value of a byte is between -128 to 127.

You can use this method to read unsigned byte:

Sub Activity_Create(FirstTime As Boolean)
   Dim b As Byte
   b = 253 
   Log(b) 'will print -3
   Log(ConvertSignedByteToUnsigned(b)) '253
End Sub

Sub ConvertSignedByteToUnsigned(b As Byte) As Int
   Return Bit.And(b, 0xFF)
End Sub

 

[hangloose99]

Is there a way to write an unsigned byte with Astreams?
e.g. the value "253" bufferTX(0)? --> AStreams.Write(bufferTX)

 

[Erel]

There is no difference between a signed byte with the value of -3 and an unsigned byte with the value of 253.

This code will work correctly:

Dim b() As Byte = Array As Byte(253)
AStreams.Write(b)

 

[hangloose99]

ok... thank you, than it seems there is a problem with my
CRC calculation. if the value for the CRC is <= 127 everthing works fine.
If the value is > 127 it won't work.
do you have any ideas?


Dim k As Int

intCrc16RX = Bit.Xor(intCrc16RX, buf)
For j = 0 To 7 Step 1 ' for each bit
k = Bit.And(intCrc16RX,1) ' memo bit 0 state
intCrc16RX = Bit.And(((Bit.And(intCrc16RX,0xFFFE)) / 2) , 0x7FFF) ' Shift right with 0 at left
If k > 0 Then intCrc16RX = Bit.Xor(intCrc16RX,0xA001) ' Bocuse
Next

Return intCrc16

 

[hangloose99]

this is the working code in "C"
Maybe there is a way to translate to B4A
:sign0013: i'm only a :sign0104:

unsigned int crc16_update(unsigned int crc, unsigned char a)
{
unsigned char i;

crc ^= a;
for (i = 0; i < 8; ++i)
{
if (crc & 1)
crc = (crc >> 1) ^ 0xA001;
else
crc = (crc >> 1);
}

return crc;
}

 

[hangloose99]

:sign0060:

buf = Bit.And(buf,0xff)

in the CRC Routine solved the problem

Thanks