convert part of a line into hex

If Perl is an option:

$ perl -lpe 's#(?<==)(.*)#join ",", unpack("H2" x length($1), $1)#e' file
some line
some other line
DisplayChoices=53,41,4d,53,55,4e,47
yet another line
ChipManufacturer=4c,47
and yet another line

I'm sure this could be improved ...

You can avoid the external process calls by setting up an awk array to translate bytes to Hex:

AWK='''
BEGIN {
    FS = "="; OFS = "=";
    for (j = 0; j < 256; j++)
        Hx[sprintf("%c",j)] = sprintf(",%.2X", j);
}
function toHex (tx, Local, j, r) {
    for (j = 1; j <= length (tx); j++)
        r = r Hx[substr(tx, j, 1)];
    return (substr(r, 2));
}
$2 != "" { $2 = toHex( $2); }
{ print; }
'''
awk "${AWK}" myFile

paul--)  awk "${AWK}"  foo.txt
some line
some other line
DisplayChoices=53,41,4D,53,55,4E,47
yet another line
ChipManufacturer=4C,47
and yet another line
ESC,%,TAB,*=1B,25,09,2A

Probably not the cleanest way to do it but with awk:

awk -F= -v OFS=\= '$2 != ""{
        "printf "$2" | od -A n -t x1 | tr -s \" \"" | getline $2;
        gsub(/^ | $/,"",$2);
        gsub(/\s/, ",",$2);
}1' input

This will use = as a field separator, and if a second field exists it will execute od -A n -t x1 against it, squeeze all spaces, trim the leading and trailing space, and convert all remaining spaces to a comma.