I don't really understand what you are trying to do. You showed the print head for the thermal printer, but did you want to try to build your own hardware for the print head, or were you going to try to use it in the POS that your friend has?
If you are thinking of trying to use the print head alone, my advice is to take the easy way out and buy a $40 thermal printer that can accept serial instructions.
If you want to use it inside the POS, then perhaps your best bet is to find out what type of POS machine it is. With that information, you might be able to google the drivers for the type of printer, or see if anyone else is trying to do the same thing. If the hardware is PC based, you might get really lucky, and have
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