In POS system, cashier computer connect to printer using serial rs232 usb or cable. We need to capture data from that connection, and parsing the data to get total amount for every transaction at POS, then send it to database server via internet. if require, using raspberry or arduino, also gsm modem to send the data. While capture the data, the POS pc still print bill normally.
Skills required are C Programming, Electronics, Embedded Software, Microcontroller, Python