Parse text file with addresses, byte values, and comments to binary file

I'm attempting to start with a file in the following form: ~~~ 00: 42 ; byte 0 is 0x42 / d 01: 52 ; byte 1 is 0x52 / r 02: 62 ; byte 2 is 0x62 / D 03: 72 ; byte 3 is 0x72 / R 07: 1f ; bytes 03..0e are implicitly 00, byte 0f is 0x1f ~~~ and use it to generate an 8-byte file whose values (in hex form) would be: 42 52 62 72 00 00 00 1f The exact input format isn't carved in stone. I just picked ';' as a comment delimiter because it's a single character and unambiguous. The form of the offset: and 2-digit hex value just seemed obvious based on tradition. I suspect the ultimate solution involves using sed or awk to strip away the comment, then piping their output to xxd, but so far my first experiment has fallen flat on its face & I can't even get xxd to parse what ought to be a best-case simple text file. --- For my first attempt, I simplified config.src: ~~~ 00: 42 01: 52 02: 62 03: 72 ~~~ (omitting the comments and implied zero-bytes for now, and sticking to values corresponding to printable ASCII) ... then tried to generate the binary file from it: xxd -r config.src config.bin What I expected to see from cat config.bin and xxd config.bin: BRbr and 00000000: 42 52 62 72 BRbr What I ended up with: a 2-byte file with unprintable content cat can't render, and the following output from xxd config.bin: 00000000: 0301 So... problem #1... *What am I doing wrong with xxd*, and how can I fix it (or is there a better approach)? Keep in mind that I really want to specify one byte value per line, and would really like to be able to automatically skip sequential values and have them automatically filled with zeroes. The... problem #2... once I get xxd to parse my file, how can I go add the comments and strip them away before xxd sees them? Note that I'm not hellbent on using xxd per se... but this is a shared web server to which I don't have root or admin access, so apt-get install isn't an option, and compiling my own copies from source wouldn't necessarily be easy). --- *(Background info... not necessary essential to solving the problem, but adding context to why I'm trying to do it)* I'm working on an Arduino-based IoT controller. For the past few weeks, its configuration has consisted of hardcoded values and various interpretations of a DIP switch I've repurposed every few days. It's getting tedious. I'm not in the mood yet to implement a proper UI, so I came up with the idea of having it just fetch a binary config blob from my web server into a char[] as its first act upon starting up (enabling me to tweak runtime config values without having to go all the way and reflash the board itself, which is honestly kind of a pain at this point).