ASCII to HEX

NeedToKnow · May 2023

Hey there brains trust. I've have been out of the AMX programming game for a while, but I am just starting to dip my toe in again. I am writing a little module that allows the user to save a number of MAC addresses (input from the touch panel as a character string: XX:XX:XX:XX:XX:XX, saved in a character array ) I have this portion working well, however I am struggling with the conversion of the ASCII representation of the HEX values to real HEX values. This is so I can construct a magic packet for Wake On Lan for each of the MAC addresses. String manipulation has always been a week point of mine. Any help or advice, or even sample code would be fantastic. ChatGPT doesn't do Netlinx very well...

John Nagy · May 2023

Consider making a lookup table in an array.

Marc Scheibein · May 2023

basically, this would be a job for HEXTOI() (hex to integer).
HEXTOI interprets an ASCII row containing 0..9,A..F/a..f as a hex representation, and converts it to a numeric equivalent.

integer nNumericValue
char sHexinAscii[8]

sHexInAscii = 'FE'

nNumericValue = ITOHEX(sHexInAscii) // converts the string 'FE' that represents a Hex value, into numeric 254 / $FE.

Don't get confused by the "I" of HEXTOI - there is no difference in value noting $FE or 254, the "integer" means "numeric"

In case of an ascii string '00:60:9f:11:22:33' , itohex() will begin to interpret the '00', but stops at the first ':', because the ':' is no hex-like character. So you may have to do some kind of loop to parse the 6 octets.

Might be easier to do a lookup table as John said, and compare the full MAC address string.

richardherman · May 2023

You could do something like this:

DEFINE_FUNCTION CHAR[6] fnMACAddressConversion(CHAR cMACAddress[])
{
    STACK_VAR INTEGER i
    STACK_VAR CHAR cMAC[6]
    STACK_VAR CHAR cMACReturn[6]

    IF (LENGTH_ARRAY(cMACAddress) == 17) //very crude check
    {
    For(i = 1; i <= 6; i++)
    {
        cMAC[i] = HEXTOI(GET_BUFFER_STRING(cMACAddress, 3)) //: will be ignored
    }
    cMACReturn = "cMAC[1],cMAC[2],cMAC[3],cMAC[4],cMAC[5],cMAC[6]"
    SET_LENGTH_ARRAY(cMACReturn, 6)
    RETURN cMACReturn
    }
}

If you call the function with a MAC address as an ASCII string, it will return that address as a numeric array:

cMACAddr = fnMACAddressConversion('80:EE:F3:DE:1C:95')

I've tried it very briefly and it does seem to work.

The function does nothing to verify that what you feed it is actually a MAC address and if not will probably fail unpleasant... But I gather you seem to have control over the input, so maybe more checks won't be necessary.
If your MAC address contains a numeric zero (common case) and you try to display that in the diagnostics windows, you won't see the string from the point on where the 0 is encountered. So if the address starts with a 0 the result seems empty... it isn't, that's just an annoying many, many, year old display bug in the diagnostics window.

ASCII to HEX

Comments