Bluetooth

I should add that the criteria isn't purely financial. There are many advantages to having a wireless connection. However, I have to keep costs down. I found a module by National that goes for about USD $16 and it integrates it all. It communicates with the MCU via a serial port. Nice, but three times what I can afford. Quantities to be purchased are 50 to 100 pieces per run.

Thanks,

-Martin

For $4 to $5, we can get FSK RF modules in 300MHz to 500MHz area. It's not bluetooth, but you don't have to pay bluetooth prices either.

Forget about bluetooth. Its total crap. Been there done that. Just finding a serial-cable-replacement dongle that works and keeps working reliably for weeks(!) is almost impossible. I'd go for a controller with internal USB.

--
Failure does not prove something is impossible, failure simply
indicates you are not using the right tools...
                     "If it doesn't fit, use a bigger hammer!"
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Atmel has a multichip thing that has a uP with analog and digital ports and ZigBee, for around $5 I think.

John

Geeee! I wonder who might have had a hand in designing the analog portions ?:-) ...Jim Thompson

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What's the deal with ZigBee in terms of regulatory requirements? I understand that testing and certification for Bluetooth can cost a bundle and that there's a steep per-product fee to be paid? I guess this makes the National LMX9838 pre-certified module well worth the money.

Still...a cabled connection is so much cheaper, even USB is not a big deal today. Not as "sexy" as Bluetooth...but when it isn't absolutely necessary...

Thanks,

-Martin

Other than the obvious dongle issue, what problems did you have? Presumably the dongle issue would not be there if you were talking to a laptop that has built-in Bluetooth functionality. Right?

-Martin

In message , martin_05 writes

Think you'll find most laptops with 'built in' bluetooth are just hiding the USB connection. There's a standard 10 Pin (IIRC) connector for the modules and it's very definitely USB plus a few other control signals to enable power management.

--
Clint Sharp

The problems where mostly firmware issues like not being able to keep up with the serial data (9600 baud!), not being able to shutdown a bluetooth connection and various interoperability problems between bluetooth devices. Not to mention the pairing process and sudden loss of the pairing data. I'm talking about dongles in a price range between 15 euro and 150 euro.

I don't know about laptop dongles or internal bluetooth devices but I guess the misery will be the same.

--
Failure does not prove something is impossible, failure simply
indicates you are not using the right tools...
                     "If it doesn't fit, use a bigger hammer!"
--------------------------------------------------------------

You could look at the RFM12B module. You'd need an RFM12B

a small USB to serial converter (such as one of these: available from Farnell), and a small micro with an SPI interface. This would form your 'dongle' to plug into the PC.

On your sensor measuring device you'd need an RFM12B.

This means all development can be done with a simple serial interface using the RFM12Bs as a wireless serial connection. Much easier than Bluetooth IMO!

Mark.

Just to add to that, the RFM12B (available in 315, 433, 868 and 915MHz variants) and is about $2.10 in volume. The serial cable is just an FTDI USB to serial chip so you could embed this on your dongle to keep the cost of that down. Point is I think is the RFM12B is reliable and very cheap, and adds little to the cost of your sensors. They are also very low power when sleeping.

Mark.

Very interesting, thank you!

-Martin

Rather than bluetooth i would think more like RFID tags.