RS-232 Devices can Turn You into a Serial Killer

In a world that is gradually becoming nearly exclusively plug and play, POS hardware has yet to catch up. A scarily large majority of affordable hardware I have to deal with is still using RS-232 communication, the antithesis of plug and play.

• First step when setting up a serial device: get the communication settings right. Baud rate, data bits, parity and stop bits. Check the devices manual to get these (the odds of getting the right information in the manual directly correlates with how much you paid for the device). The flow control will be set as ‘None’ unless specified otherwise.
o Changing communications settings is a whole new thing on its own. You can edit the values by right clicking on the port in device manager and viewing its properties. A better way to do it is via a mode statement in the command line. The syntax for that is:
mode com1:9600,n,8,1
Where com1 is the port, 9600 is the baud rate, n is the parity, 8 is the data bits and 1 is the stop bits. Change as need be.

• Next, check if that com port is open. Run mode com1 (if the port you are trying to use is com1) in the command prompt with all programs that you know of that use that port closed. If it is open and available, it will return the communication settings. If the port is in use, then it will say Device COM1 is currently unavailable.
o Common software culprits that hold open com ports (in my experience) are the following: OPOS drivers, any kind of physical device drivers, USB to serial (or vice versa) conversion software, printer drivers (including remote ones that have been mapped back to a com port, run the net use command for more info). Check your msconfig startup tab for anything that runs and claims a port.

• If you’re still having trouble, disabling and enabling the com port in question via device manager has gotten me out of a tight spot. Keep in mind; this might only temporarily stop whatever was claiming the device.

• If you’re finding your device becomes unresponsive after a restart, then you could put the mode statement mentioned earlier into a batch script and put it in the startup folder.

• Hyperterminal is a program (probably not the best, but it will do) that can communicate with serial devices (I use it mostly with scales) that comes with Windows XP. Vista and Windows 7 users will need to yank the executable and .dll files off an XP machine.

• Some serial devices are still made with their own customer cables needed – if you can’t get any from the supplier or manufacturer, then you’re going to have to test out your soldering skills. Usually the manual or manufacturer website should contain a cable guide, with different cables for different POS systems. Since we run Amicus on Windows operating systems, the IBM 9-pin cable configuration works for us.

If you’re still struggling, you should probably stick to parallel and Ethernet solutions. No matter how used you get with serial devices, they will always find a way to throw you a curveball.