I was finally motivated to get my hands on some Bluetooth hardware so I could figure out why my latest ASCOM driver wouldn’t work with Bluetooth. I found mine at U. S. Converters. I needed two–one that would plug into a USB port on my notebook (I bought model BLDONG for $9.99), and one that would plug into the serial connector of my digital setting circles interface (BT232B for $45.00). The BT232B serial Bluetooth adapter also requires a gender changer because it has a female DB9 connector just like my DSC interface, so I bought 10GC-D1 for $7.99, too. I know that AirCable sells this kind of stuff, too, but U. S. Converters seemed a little more economical.

Now it was time to get it all hooked up and functioning.

The BT232B adapter needs to be powered. There are three options:

  1. a USB cable (only for power, not data)
  2. an external 3V – 5V battery (not included, but a small cable and connector are included)
  3. 5V at pin 9 of its DB9 connector

I chose option 3. Since my DSC interface board already has a 5V supply available, it’s a simple matter to feed it to pin 9 of the DB9 connector (note, however, that this combination will consume more than double the current of the DSC interface by itself, so you’ll want to use something bigger than a 9V battery to provide power). Here’s a photo of how I installed a small jumper wire on the underside of the board to provide the 5V at pin 9 (click to enlarge):

DSC board with jumper to provide 5V to pin 9 of the DB9

Be careful that the jumper wire doesn’t short with any other circuit board traces.

Once the board is providing 5V to pin 9 of the DB9, you’ll need to set a switch on the BT232B. There’s a switch that determines whether it’s expecting power on pin 9 or from the USB or external battery. Set the switch so that it expects power from pin 9. As a test, you can plug the BT232B into the DSC board (using the gender changer) and then power up the board. The BT232B Power LED should glow red, and the Status LED should flash blue.

The next thing you’ll need to do is configure the BT232B for 9600 baud, 8 data bits, 1 stop bit, no parity, and no flow control. The included instructions tell you how to do this, but the basic procedure is to set it for DCE (there’s a switch on the side to change it between DCE and DTE, depending on whether your plugging it into a computer or another device like the DSC board), plug it into a serial port on your computer (or through a USB-serial converter), give it power (the USB cable is convenient for that, but change the power selector switch), and then connect to it using Hyperterminal at 19200 baud, 8 bits, 1 stop bit, no parity, no flow control. you can then type commands in Hyperterminal that will change the configuration of the BT232B.

First, type “AT” (without the quotes) and hit the Enter key. The BT232B should respond with “OK” (again, without the quotes). If not, double check your settings and switches and try again.

Then type the following commands:

  • FLOW=N
  • BAUD=9600

After each command the BT232B should respond with some sort of confirmation of the command. However, after you set the new baud rate, Hyperterminal will no longer be able to communicate with the BT232B because the baud rate was changed. Don’t sweat it–you’ve done everything you needed to do.

Now you should be able to disconnect the BT232B from the computer. Set it for DTE and for getting power from pin 9 of the DB9, and plug it back into the DSC board, and power it up. If your PC doesn’t have built-in Bluetooth, you’ll need to insert your USB-Bluetooth adapter into a USB port (don’t forget to install any drivers if needed–check the documentation).

Now turn on Bluetooth on your PC and connect to the BT232B. Usually this is done by right-clicking on a Bluetooth icon in the system tray and selecting Connect from the menu. Windows will search for nearby Bluetooth devices and give you a list from which you can choose the serial Bluetooth adapter. Once it’s connected, it will hopefully report which COM port it’s configured as. If not, go into the Device Manager (right-click on My Computer in the start menu and select Properties from the context menu) and look at the list of ports to determine which port number is assigned to the serial Bluetooth adapter.

If you want, you can use Hyperterminal to connect to that port (9600 baud, 8 bits, 1 stop bit, no parity, no flow control) and test the connection. Once Hyperterminal connects to the port successfully, the flashing blue LED on the BT232B will stop flashing and glow steady blue. Try typing “H” and “Q” (without the quotes) and see if you get a response from the interface. If not, go back and double-check your steps and try it again.

Now you’re ready to use your favorite astro software with the DSC interface via Bluetooth. Just make sure that you set the COM port in the Settings to be the one for Bluetooth.

Let me know how it goes.


9 thoughts on “Bluetooth Adapters for My Digital Setting Circles

  1. Dave I’m trying to set my system up with the BT232B and the USB dongle on my laptop and am having trouble. It won’t stay in sync. (blue light starts flashing) I’m very close so it is not a weak signal. I was wondering how you had the switches set on the BT232B. Slave or Master and group or no group?


    • Pat, mine’s set up with the DCE/DTE switch set to DTE and the two DIP switches set to M and G. the USB/Battery/DB9-Pin9(5v) switch on mine is set to DB9-Pin9, but yours probably needs to be different if you’re powering it with the battery or the USB cable. Did you change the baud rate for the converter to be 9600 baud?


  2. Hi Dave

    I am using the BT-232B adapter with my Ouranos DSC box. I have used the settings PARITY=N, FLOW=1, PARITY=N and BAUD=9600. When I connect to it with terminal software and send the command “Q” I expect to recieve -02000-02000 (the values in angle brackets are hex codes).

    Instead I am getting -0200B. (I am ultimately wanting to connect to Sky Safari on my HTC Desire Android phone.) I can only assume that adapter is not receiving the output from the box quick enough. I have tried other terminal software, including terminal software on my phone, I get the same result.

    Have you experienced this issue with your DSC card? Do you think I have a faulty adapter card? Do you recommend that I purchase your DSC card?

    Many thanks for your attention.


  3. Hi again Dave

    I’ve just noticed that my earlier posting does not show what the hex codes which I had put between angle brackets – your message board must have removed them.

    So, to recap (using square brackets this time for hex codes) – I was expecting:


    But when using the BT232B adapter I was getting:

    -02000[92][82][82][82] i.e. garbled data.

    I am able to successfully communicate with the Ouranos box via a serial cable with my PC’s serial port, using 9600 baud, no parity, no flow control and no parity as given in its manual.



    • Keith, in your first post you indicated that FLOW=1, but I assume that you meant FLOW=N. Regardless, double-check to make sure all your settings are correct: 9600 baud 8 bits 1 stop bit no parity no flow control. Also, make sure you’ve switched the BT232B to “DTE”. Beyond that, I’m not sure what’s wrong–I haven’t run into that problem myself.

      Good luck –


  4. HI DAVE,
    Been using your DSC setup for a while and am moving to Bluetooth.
    I have a small 12v lawn tractor battery I want to mount in the base of my dob with the DSC box. Think that would work for power using your option 3 above? Just don’t want too little or too much power to the box.

  5. Dave,
    Given the limitations on the Ipod Bluetooth I went instead with a serial WiFi adapter (WA232 from USconverters) and the gender changer. Most of what you say applies here too, including the power jumper. Just connect with a terminal program (the WA232 is already in 9600-8n1) and configure the IP settings. With an existing Wifi I used
    set ip dhcp 0
    set ip address 192.168.1.nnn
    set wlan join 1
    set wlan ssid
    set wlan phrase

    On the Ipod, DS Browser can talk to it, but I am having a bit of trouble with Astromist at the moment. As an IP device it is accessible from multiple hosts, so it might be possible to have more than one app on different systems monitoring telescope position.

    In the absence of an existing wifi network, eg out in the field, I believe the device can be configured to create an ad-hoc network that a handheld could connect to.


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