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I know my questions must seem random. I'm still in the infancy stages of programming, and play with different products in my spare time. I picked up a Parallax RFID reader as we work with RFID quite a bit in my line of work (automation). I have previously taken this technology for granted and just interfaced (expensive) off-the-shelf devices to a PC or PLC.

To the issue at hand... The parallax RFID reader returns 10 alphanumeric hex digits in to a string array. Obviously a 10 digit hex value is too large for a LONG variable, so I have broken it into 2 longs. Is there an easier way to convert ascii hex values to numbers that can be used for math? I can include the rest of the code, but this is the part I'd like to simplify. I'm checking to see if the current BUFFER value is a number or a letter, and then subtracting the appropriate amount to get the hex value.



If I scan a tag with value 3600A397A8, I will end up with the ascii equivalent of each digit in BUFFER. The code above takes BUFFER and makes 2 long variables containing 3600A and 397A8. And yes, I already noticed my high and low values are swapped with regard to lsb.

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Studio 2.0.0.16 on Win 7 Home x64 updated daily - Original Roboclaw 5A V1.3.9
Mostly a Nano40 for prototyping, but I have others in my bins

That is more or less the way that I do it, when I don't know for sure the buffer will have the appropriate values... I may use ASCII characters in my test and calculations as to make it easier to read...
Things like:

But if your hex strings are being read in by something like a SERIN command you can also do this by using input modifiers. Something like:

I made the arbitrary decission to pack the lower 8 hex digits into a long and the top 2 into a byte, but you can choose how many characters to process by each...

Kurt

But if your hex strings are being read in by something like a SERIN command you can also do this by using input modifiers. Something like:


I am going to give this a try. I like dealing with numbers more so than characters. Thanks for the snippet.

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Studio 2.0.0.16 on Win 7 Home x64 updated daily - Original Roboclaw 5A V1.3.9
Mostly a Nano40 for prototyping, but I have others in my bins

It works... kind of. Studio doesn't allow a minimum modifier on an input, so the line becomes:



This works for many cases; tag values that don't start with a 0 as the first digit. If the first digit of the tag is 0, the code breaks. i.e. for tag 0800D9D837, the first 0 gets dropped. So HIGHVAL gets loaded with 80 and LOWVAL with D9D837. Any suggestions for catching that first 0?

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Studio 2.0.0.16 on Win 7 Home x64 updated daily - Original Roboclaw 5A V1.3.9
Mostly a Nano40 for prototyping, but I have others in my bins

Read in 8 first and then read in 2. It will exit the read of 2 of you receive something other than a hex number for the second digit(eg you send "02 " it ignores the 0 reads and converts the 2 then sees the space and returns the 2 to the specified variable.

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