My employer recently "upgraded" my laptop to a model that doesn't include a serial port. I've got lots of USB/serial converters based on the Prolific 2303 chipset, and have used this chip for ages on various platforms, but the Windows 7 drivers for this chip have not worked well for me.
Rather than roll the dice with other chipsets and drivers, I decided to get what I really wanted: a bluetooth serial port from BlueConsole.
Bluetooth is a huge advantage for me because it allows me to go find a chair while working in sometimes hostile environments (data centers, construction sites, manufacturing plants, mountaintop antenna towers), rather than do the balance-laptop-on-left-hand-while-typing-with-right-index-finger ballet.
Unfortunately BlueConsole is out of business, so I had to find something else.
The UConnect BT232B is the best solution I've found, and I'm happy enough with it to recommend it. I got mine from US Converters.
It has some shortcomings:
- It has thumbscrews instead of fixed female threads
- The DE-9 connector is female, rather than male
- It requires external power (either mini USB or through a small battery connector)
The thumbscrew problem was the easiest to resolve. Remove thumbscrews, replace them with 4-40 hardware scavenged from an IT junkpile. Three screws hold the plastic clamshell together, but two are covered by the sticker. Sticker carnage:
For power, I use an Energizer EnergiStick 250 charging dongle intended for cell phones. It's a small 250mAh rechargeable battery with two mini-USB ports: A male port for powering the adapter, and a female port for recharging. This 250mAh battery should last almost 3 hours at the BT232B's rated maximum draw (90mA). I've used it for at least twice that long without recharging, so the actual current consumption must be quite a bit lower. Maybe I'm not typing fast enough :-)
It's like it was made for the BT232B:
Pass-thru charging is supported: The Energizer battery can take a charge from a USB source while simultaneously powering the bluetooth radio.
The BT232B pairs easily with both Windows 7 and OSX. Both platforms install it as a locally attached serial port: COMx in Windows and /dev/tty.mumble in OSX. Its baud rate defaults to something other than 9600 baud. I configured it once, and have not had to reconfigure it, so either it remembers its settings, or it's taking cues from my terminal emulator software.
The Windows 7 bluetooth drivers are kind of terrible. If I'm linked up with the device and put my laptop to sleep, I need to delete the port and re-add it in the control panel in order to get it working again. Under OSX it just works.
The radio performance has really surprised me. I'd expected it to give me just a little bit more room to roam than the normal 6' Cisco cable, but it's way better than that. I've used it over 50' in data centers, and 60' (through walls) in my house. When it gets to the end of its radio range, it tends to get weird and slow, but doesn't drop characters.