I have always disliked using serial console connection to a switch or other network device with my laptop. The serial cable just ties me to that particular place and device. Depending on the situation you may have options like using a console server or a dedicated management network connection. But every now and then the serial console connection is needed anyway from the laptop, like when first configuring something, having a maintenance break or just labbing up. USB console connections are maybe getting more common but I haven’t had the honor yet to see it in any of the devices I’ve had to console in.
Nowadays we don’t even have serial ports in laptops anymore so an auxiliary gadget is needed: a USB port to serial port adapter. And that creates another pain: There are major differences in USB-serial adapters regarding their OS support and driver stability. BSODs have been common with some drivers and adapters. I’ve witnessed a case where a network specialist was dealing with a major network issue but the access to the affected switch (and hence the progress of the whole incident) was severely disrupted due to the laptop crashing all the time due to the USB-serial adapter. Luckily there was another specialist nearby who had a USB-serial adapter of another brand, and the case could be resolved right away.
Due to all these reasons I wanted something different: a Bluetooth serial adapter. After some delivery and communication problems (neither of those – delivery or communication – really happened) with one store I managed to place an order in another store for Sena Parani-SD1000 (www.senaindustrial.com; updated the link at 14-Jul-2014) adapter with accessories.
There are several ways to use these kind of adapters, like replacing a long serial-to-serial cable by using two of these adapters and pairing them together. In my case I’ll just use my laptop’s built-in Bluetooth feature to pair with SD1000 so I need only one of these adapters. And, there is no special driver required to run it! Just the normal Bluetooth stack software.
The features in short:
- DB9 female serial connector, max speed 921600 bps
- Bluetooth 2.0 + EDR (SPP = Serial Port Profile)
- DC power connector for external power supply/charger
- Stub antenna (there are various antenna options for longer reach if needed)
- DB9 female-to-male converter
- USB-to-DC cable for power/charging
- AC power adapter with DC connector for power/charging
- A power lead with DC connector (for custom power installation)
- Standard battery pack.
The power can be supplied in various ways:
- battery (Standard and Extended) (optional)
- USB-to-DC cable (included)
- AC power adapter (optional)
- DC cable (just a piece of cable with connector so that you can feed the power from various sources) (included)
- pin 9 of DB9 connector (it’s up to your serial device).
The pin 9 option means that in some cases you don’t have to do anything special to get the thing powered, just plug it in the serial port. To be on the safe side (my guess is that Cisco-style RJ-45 console ports don’t deliver the power) I ordered the Standard battery with my adapter. The AC power adapter is not necessarily included, depending on the package, and the battery is not part of any manufacturer-provided packaging, it has to be purchased separately.
In addition to the Standard battery there is also an Extended battery available. As expected the battery makes it possible to use the adapter without connecting external DC source. According to the specifications the Standard battery is supposed to last about 4.5 hours and the Extended battery about 16.5 hours, depending on the usage. If the battery is not present (or is empty) and pin 9 power is not available, a DC source is obviously needed. The battery will automatically charge when whatever DC power is connected.
The Standard battery is very slim and doesn’t practically add any weight to the adapter (which is light as such anyway). It’s only a couple of millimeters thick and can be seen below attached to the bottom of the adapter.
The serial connector is female DB9, which means that if you want to connect it to a Cisco-supplied rollover console cable you need to use the included female-to-male converter. Not a big deal. In addition to the rollover cable I carry a DB9-RJ-45 adapter with me so that I can plug the rollover cable to a DB9 device as well. You may ask why I wanted to do that as the adapter itself already provides a DB9 interface. There are two reasons I presume I’ll use the cable anyway: First, if I’m working far enough from the adapter I can position the adapter with the serial cable to a better place for larger Bluetooth range. The second reason is the battery charging: If the battery is empty (and pin 9 power is not available) I can maybe find a USB port somewhere near so that I can power and charge the adapter while using it. The USB-to-DC cable is only about 30 cm so that may not be enough alone. And I need some kind of rollover cable anyway with me so the small adapter is not too much to have in the bag anyway. The rollover cable can be shortened if needed.
Using the adapter
As you can see from the topmost image there are some buttons in the adapter. The power switch is not shown, it is on the side of the adapter. The DIP switches are used to set the serial port speed and flow control, and the speed can also be controlled in software. Basically the adapter also obeys some AT commands. I haven’t touched them, read the manual from the manufacturers site if you’re interested. I just set the switches to 9600 bps and continued. Keeping the Pairing button pressed a couple of seconds using a paperclip it starts to look for a partner. At this point the Bluetooth discovery can be started in the computer. The adapter presents itself as “SD1000v2.0.8-xxxxxx”. After pairing there were two COM ports added in Windows 7. I don’t actually know yet why there are two ports, I have just used the first of them (COM8) and been happy with it. The PIN code was 1234 and it can probably be changed with some AT commands.
In the following uses it is enough to just switch the adapter power on and it will automatically pair with the last partner. Again, there can be some even more sophisticated logic but that’s how I’ve used it this far. The console connections with laptop cannot get any easier than this!
The few occasions I have used the adapter so far I’ve been extremely happy with it. It is easy to use and gives me the flexibility I wanted. The price (about 130 EUR with all the accessories above and shipping from Sweden to Finland) is quite high but good stuff always tends to cost something. I got mine from LAWICEL (www.lawicel-shop.se).
I haven’t really explored all the adapter options yet. For example, the data sheet says it supports up to 4 simultaneous connections. I guess that is something good.