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Basic Electronics » USB cable and Bluetooth dongle ...

August 21, 2010
by paraplegic
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I'm trying to get my head around replacing the USB serial connection with a bluetooth link to my PC. Assuming the that USB cable has the FTDI circuitry to change the 12v to ttl/5V for the Nerdkit, could one not then just stick a USB adapter and a cheap Bluetooth USB dongle on the end of the cable and pair that with the PC???

I see that Sparkfun has all kinds of $65 adapters, and smirfs and stuff, but I'm not sure why a $10 USB cable and a $12 USB bt adapter can't do the same thing?

August 22, 2010
by Ralphxyz
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Wouldn't you also need to supply power?

The USB cable plugged into the PC is powered by the PC if the bluetooth dongle replaces the PC's power source where does the power come from?.

Also a bluetooth dongle needs a associated driver where would this driver reside?

Since I do not have the slightest idea what I am talking about I find your concept interesting.

I am also always looking for the least expensive way of doing things and right now wireless communications between the NerdKit and PC or other devices is growing in interrest.

So if I could get bluetooth for $20.00 instead of $60.00 that would get my interest.

Ralph

August 22, 2010
by paraplegic
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Ralphxyz, I believe that the USB standard allows it to deliver 500ma at 5v, IIRC. Power is not the issue, it is rather that the dongle has the ability to act like a serial port, and the USB cable has the FTDI circuitry to connect the dongle to the AVR. I'm just looking for a bit of guidance, here ...

August 22, 2010
by Ralphxyz
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That is correct a "standard" USB cable "plugged into a computer" will have 500ma at 5v.

If I understand you correctly the USB cable would be connected to the Nerdkit, not to a computer, as currently done, with the bluetooth dongle in the end. So where is your power source? Possible you could plug the red wire into the hot rail (+) but where would you get your ground?

Again I wish you well, I would hope someone with more knowledge would jump in here and give us some guidance. As I said before this would be interesting.

Maybe I am not understanding your proposed wiring correctly.

Ralph

August 28, 2010
by hevans
(NerdKits Staff)

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Hi all,

Ralph's explanation about the driver requirement is spot on. When you connect a USB/bluetooth dongle to your computer, it is connected to a complicated USB software stack and a driver for your dongle (this bluetooth module might be internal to your computer). You can't just connect a USB/bluetooth dongle to the end of the USB cable because there is no USB stack or driver on the NerdKit to drive a USB device. Notice how both the USB cable and the USB/bluetooth dongle would be the male end of the USB connector. Both of these devices are a USB devices that would need to be connected to a USB host for it to work.

There are however, bluetooth to serial devices out there that could connect to the NerdKit via the UART link. That would then connect to your computer via bluetooth and most likely show up as a COM port just the way the cable currently does.

Hope that clears things up a bit!

Humberto

August 30, 2010
by paraplegic
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Thanks, Humberto. I suppose I'll have to drop $60 or so on a USART bt interface ...

September 01, 2010
by Hexorg
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Also dont forget that USB needs a Host-controller to operate. BT dongle and USB serial adapter are clients. Correct me if i'm wrong, but you can't connect two usb clients together, without a host controller (like your PC has)

September 14, 2010
by zrouse
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Just a thought,... I am definitely new at this.... So I was thinking of how to connect wireless to my mcu when I reading through your posts the other day.
Later that night it came to me, i have an old bluetooth headset, could the be used? My thinking is that it is a transceiver so what is it limited to transceive? I was thinking for using your input to the mcu would be the line going into the to the speaker on the headset, and the information going away could ride on the microphone side.

I would assume that you would have to set something up on a count method... Again, I am just starting to learn code... I wouldn't know how to begin writing it to use this application, Although I am going to pursue searching if this method is possible. If anyone does figure it out, that would be awesome. otherwise it was just a thought.

September 14, 2010
by Ralphxyz
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The problem is you do not have a interface from the MCU to the bluetooth module, true you could "program" one but good luck with that and keep us posted (I want this also). In the mean time because we do have the UART interface why not communicate with some inexpensive rf modules? Receiver Transmtter

Now for <$20.00 plus shipping and tax you would have wireless communications, and any programming that is done would be a start on implementing a bluetooth connection.

Ralph

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