Trim a single bit from a byte?

Question

OK so im a mechanical guy, not a programming guy so lets start there.  I just learned how hexadecimals work and have limited experience in LABview.  I have been searching this topic for days, maybe its just my vocabulary but I havent found anything.
I need to analyze a signal coming from a CAN system.  I dont have the can device yet but I'm accessing position sensors on the system.  They come in as 8-bit hexadecimal messages.  I am currently simulating this message as a string in LABview so i can get one part of my program ready.  The manufacturer has given me example code that requires concatenating two bytes but I only need 3 of the bits to be concatenated. (one needs the last bit trimmed and the other 2 need the first bit trimed.)  I have already concatenated the two bytes necessary but cannot figure out how to get rid of an individual bit.  I need to do this as hex values to get the proper measurements.  I know my programming grammar is probably a bit off so let me give you an example.
Example String of Hex Values
03 23 F6 21 B4 C4 74 F6
The first sensor requires bits 3 &4 (21 & b4)
In this case they are required to be in the order 4,3 and drop the first bit to receive 421 as the needed hex value.  So far I have made an input string to simulate the incoming CAN message with that 8bit hex values.  I then use string subset to isolate the individual bytes and finally concatenate to get them in the correct order and end up with B421.  I cannot figure out how to drop the "B" bit or replace with a zero.  I can only replace the full byte.
Is there an easier way to do this.  I plan to use the example VI to receive the CAN messages which outputs to a string, hence why I am using strings.
Thank you in advance for the help.  I am going crazy trying to figure this out.
Also if any other details are necessary please let me know

Answer 1

jpc335 wrote:
I was told by the manufacturer that the 3 bit hexadecimal string can then be converted into usable numbers.  So if its faster/easier to replace the first byte with a 0 or turn it into a 3 bit hex string.  Either will work.
You want to break yourself of this misuse of bit ASAP.  A bit is a single 1 or 0.  Hex requires 4 bits to find the values.  The purpose of hex is to reduce the number of bits you must write out so things are easier to read.
0000 - 0
0001 - 1
1010 - A
1111 - F
When you have two hex digits, you have 8 bits, or a byte.  You're talking about two entirely different conversations when you ask how to extract a bit or a byte.  It's generally easier to pull out the byte.
You'll also want to be careful with words like "third."  You're not looking for the third byte.  You're looking for the fourth byte.  WIth zero-indexing, it could be the byte at index 3.  But, you're creating confusion when you use third to mean fourth.
In terms of solving your problem, it sounds like you're going to have a string of characters.  At this point, it's relatively meaningless to view them as hex.  The environment sees them as a string and will operate on them as such.  You can use string parsing VIs to remove the parts of the string you don't care about.  If the format always looks like what you showed us, it wouldn't be hard to traverse through the string by looking for spaces.  From there, you'd need to worry about whether you need the values to be in a numeric type or if string is still sufficient.  But, you should handle splitting off only the string values representing the two bytes you're worried about.  Once you can do that, you can take the next steps.