Modify Minimosd Max 7456

Hey guys I was wondering if anybody could modify, or guide me to modify the code it's used for minim osd to read from serial(rs232/TTL) at 2400 bauds and display that counter on the screen, nothing else. I have tried with minim osd extra conected to Crius aio Pro 1.1 running on Megapirate ng and is displaying the information that comes from Crius, but i want to be able to use just the minim osd board to overlay a small counter on the screen. Here's the link to the code: