Micro Innovations USB to RS232 Serial Adapter - Serial adapter - USB - USB, RS-232
price: $16 - $35

Keyspan USB Serial Adapter USB Adapter
price: $24 - $35

Prolific chipset

First I’ll talk about the TRENDnet, Micro Inovations and Bafo as a group, they are all based on the Prolific chipset.

Physical

The TRENDnet and Micro Innovations are virtually indestinguisable having exactly the same one piece design with built in 18inch cable, The Bafo adaptor has a separate USB cable Type A to B. the cable is a generous 6 feet, and has the benefit of being replaceable with any cable for longer or shorter runs. Personally I only need about 4 inche cable and all 4 devices have to long a cable for my preference.

History

I had previously given the BAFO a very bad review having had major problems with actually using it with devices, it performed most of the time communicating between 2 computers, but devices like my Sony EVI cameras and Autopatch video switch just could not lock on the signal. And even with a computer to computer connection I logged corrupted messages, about 1 in 10 messages were corrupted. So I have had 3 Bafo adaptors sitting in my drawer for a couple of years. Now I need serial ports on USB only PC’s again lets see if the XP drivers solve any of those problems.

Software

Again the The TRENDnet and Micro Innovations have exactly the same prolific reference drivers on the CD. Bafo has it’s own installer program but it uses the same prolific drivers as the other adaptors, and all the devices are completely interchangable.

Real world testing:

At first I had the same results with these devices as I had in the past, in that I could not get them to communicate with my Soni EVI camera with the VISCA RS232 protocol, however the unusual thing is that after installing the Keyspan USB Serial Adapter and using it with the VISCA camera I was then able to connect with any of the prolific adaptors and control the camera effectively. I have not been able to determine the reason for this.

TRENDnet and Micro Innovations

Bafo 810

Tips

The COM port assignment is linked to the USB port that you plug them into, not to the device itself; so after you install any of the adaptors on a USB port and it is assigned COM3 any of the prolific adaptors plugged into that phisical USB port will always be COM3. An important thing to know is that the port numbers are assigned in the order that they are discovered and has nothing to do with the phisical placement of the USB port. That means it is the order you plug them into your computer which gives them the COM #.

For ease of use I recommend that you always use the same USB port and therefore keep the same COM # if you only use one adaptor, this way your software which probably allways looks on the same COM port will work without reconfiguration.

Or if you use lots of adaptors install them from left to right (or whatever order makes sense to you) so that the COM port numbers are sequential and easy to figure out. It is also important to note that–as with all USB devices–if you add a hub when you plug the adaptor into one of the hub’s USB ports it will be discovered yet again and receive yet another different COM port assignment. This can get really confusing if you have a couple of hubs and you plugged things in randomly the first time, but you can manualy change COM ports and get things sorted out.

One more tip, when you disconnect the adaptor (or most serial port devices like a modem bluetooth IrDA device) the COM port remains allocated but does not show up in Device Manager, however you can re-use that COM port by manually selecting it if you know that it is really free. As far as I know the only way to completely free that COM port so that it is not reported as “In Use” is to plug the device in so that it shows up in device manager, then right click it and choose uninstall. (or to go into the registry and manually remove the assignment)

Keyspan USB Serial Adapter USB Adapter

Physical

Like the Bafo it comes with a separate USB Type A to B cable but just 3 foot this time. The Keyspan adaptor is a significantly larger than the prolific devices, about twice the size, but still a fairly small device. It includes a greed LED “power” light that flashes at 1 second intervals when plugged into the USB port, and lights up continuously while sending or receiving data.

Software

The keyspan also comes with it’s own software. The first tab shows the attached devices and their port assignments, the second shows and lets you edit the settings for each.

Conclusion

However the best thing about the Keyspan is not the configuration utility but simply that this adaptor works flawlessly with all the devices I tried with it which is the point after all. Defiantly the best of bunch, though costing about two to three times as much as the other devices, I’ll still use my prolific adaptors if they continue to work well, but I certainly won’t buy anymore.

Future

Keyspan also offers a 4 port version that sells for around $150, However since that is more than The cost of 4 single Adapters and a USB hub ($24×4 + $12 = $108) I opted to purchase 4 single adaptors, but the 4 port may still be worth the extra cost to cut down on the tangle of cables.There seem to be a couple of other brands offering 4 serial port adaptors as well but at about the same cost as the keyspan, and considering the quality of keyspan’s single port product I expect to upgrade to the keyspan 4 port when I get to the point where I need to drive even more serial ports.

In the mean time I’ll use what I have and you can expect to see a review update of trying to run 4 heavy traffic applications on the prolific or keyspan devices at the same time.