Q. USB-シリアルポート変換機について(USB to Serial Devices: Just Say No!!!)[英語]
I've been beating this drum for about 2 years now. One of the most common hardware problems that we hear about is that the USB-to-serial devices always seem to be doing something screwy. We've seen everything from latency issues to flat out not being recognized by the operating system.
These devices, at one time, seemed very promising indeed. The truth about these devices has manifested itself over the last few years. The problem is that the "serial ports" they create are NOT real serial ports. They are considered "virtual" serial ports requiring the use of proprietary drivers that are not the standard Windows(R) communication drivers which Hypack(R) naturally prefers.
Other unadvertised limitations include:
Power loss over extended distances. (Any USB cable over 20 feet will seem to malfunction.)
If you use a USB port hub, it appears there is a power dilution effect that is directly proportional to the number of outlets in the hub.
High traffic sensors such as multibeam units, as well as heave, pitch and roll sensors, seem particularly susceptible to transmitting bad data. The advertised data rate does not reflect reality. I even had one unnamed company tell me that their device was not even compatible with GPS.
To be fair, some users have had success with USB to serial ports. All I can say about that is “wow” and “congratulations”. This may work for some very simple applications like one GPS and one echosounder. But if you ever come up with some funky data, don’t say that I didn’t warn you. Hypack®/Dredgepack®/Hysweep® cannot make a silk purse out of a sow’s ear. Bad data in, bad data out. The units made by Comtrol seem to have been the most successful. They have a network-to-serial device that seems to do trick much better. The bottom line is we just do not recommend them! We like the PCMCIA /PC Cards made by SOCKET I/O they have a ruggedized adaptor that precludes the use of duct tape to keep everything intact.
As of last year a “new” universal protocol for USB was adopted. USB 2.0. This promises to correct the data transfer “speed” of the previous incarnations of USB (1.0 and 1.1). The new data rate is supposedly equivalent to firewire. We shall see. The trick here is that you may buy a new computer with a USB 2.0 port but, if your USB-to-seria device is only USB 1.1 compliant, then you will gain no benefit from the new 2.0 protocol. In other words, you need both the computer and USB device to be the USB 2.0 code compliant. It remains to be seen if this will be acceptable for hydrographic surveying, as I have not seen any USB to Serial products for USB 2.0 yet.