How to split a 16bit value into MSB and LSB?

Using Arduino Programming Questions
#1

Hi,

I have values between 0 and 65536 and I would like to get the high byte (MSB) and the low byte (LSB) of it.

For example my value is 2400 decimal:
2400/256=9,375 --> 09 is the High byte. 9,375-9=0,375 --> 0,375*256=96 --> 96decimal to hex = 60 --> low byte = 60

I have tried the following:
LoByte = HighThreshold & 0x00ff;
HiByte = (HighThreshold & 0xff00)>>8;

The result is 96 for LoByte and 0 for HiByte, so this is wrong.

LoByte = lowByte(HighThreshold); //found in wire.h
HiByte = highByte(HighThreshold);
The result is 96 for LoByte and 0 for HiByte, so this is wrong too.

The solution is within my reach but I can't find the last piece in the puzzle. So any help is greatly appreciated!

#2

Post the rest of your code, using code tags ("</>" button). That is where the problem is.

#3

Your formulas there are perfectly correct. If you just set HighThreshold to 2400 and run it through those you will end up with LoByte = 96, HiByte = 9. Naturally, HighThreshold must be a datatype that is 16 bits large.

uint16_t HighThreshold = 2400;
byte LoByte = (HighThreshold & 0x00FF);
byte HiByte = ((HighThreshold & 0xFF00) >>8);
Serial.print( "High Threshold: " );   Serial.println( HighThreshold, HEX );  // <-- prints 960
Serial.print( "Hi Byte: " );   Serial.println( HiByte, HEX );   // <-- prints 9
Serial.print( "Lo Byte: " );   Serial.println( LoByte, HEX );   // <-- prints 60

Is this not what you see? If not what are you getting? I will suggest that you have either mistakenly assumed that your HighThreshold value was set to a value that it was not set to, or that you typed it with a size less than 16 bits. And you have blamed the mistake on your code. But the code is fine.

#4

Thank you very much for your help! After reading your answer and looking at your code I saw the mistake. I have used uint8_t for HighThreshold...

Now it is working as it should :slight_smile: Sometimes I don't see the wood for the trees :smiley:
Thank you very much again!

#5

rookiebalboa:
... Sometimes I don't see the wood for the trees :smiley: ...

Evidently there exists no human that can.

#6