Recently involve in POS System, and I facing a problem that client don't buy receipt printer, without receipt printer the cash drawer won't open. I found an solution, is Cash Drawer trigger DT-100U, this device will kick open any standard cash drawer protocol, below is how I integrate the solution to opensouce pos. The trigger device will kick when receive ANY message from USB port, exe the cmd below 1 by 1, you will have your cash drawer open. # sudo chmod 777 /dev/ttyUSB0 pls note that not always is ttyUSB0, is can be ttyUSB1 or 2 3 .... # echo -en '1' > /dev/ttyUSB0 your cash drawer should opened now......