Arduino UNO + Bluetooth module headaches

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1

Hi all,

I am trying to get my Arduino UNO R3 to communicate with a bluetooth module and write characters sent over bluetooth serial to an LCD attached to the arduino.

Bluetooth module (http://www.lctech-inc.com/Hardware/D...d-4d58c2b3c0cb)

So far I have proven the Arduino and LCD using the 'SerialDisplay' example sketch by sending characters from hyperterminal through a MAX232 then to the arduino - works a treat!

I have also used hyperterminal to prove the bluetooth module. I had an android app that can send characters via bluetooth, which the module sends vi aserial through MAX232 to hyperterminal. Works great.

However, when I connect the bluetooth module directly to the Arduino and use the android app I get nothing on the LCD screen.

Any ideas why this is not working?

The bluetooth module has inputs for 5V & 3.3V, I have found that it wirks fine with hyperterminal at 5V only.

2

I would eliminate "... through a MAX232 then to the arduino ..." Since the Bluetooth is TTL signaling.

You may need a 3.3V to 5.0V voltage-level converter or a resistor bridge if the Bluetooth module is 3.3V

Alternately, you could use a 3.3V Arduino Mini if the Bluetooth is 3.3V

I will leave the resistor bridge solution to your research as it is not the optimum of solutions.

IF your Bluetooth is 5.0 Volts, I do not know the problem... Maybe signal inversion?

Ray

3

Firstly, thank you for replying and helping.

I was just using the MAX232 to test both serial connections with hyperterminal (both communicate fine using this method), it won't be in the finished circuit.

Perhaps you are right on the voltage front. I think the serial from the Bluetooth device is at 3.3V. So I'm guessing I just need a voltage divider to take the 5V from the Tx of the arduino down to 3.3V for the bluetooth module?

Should the arduino Rx be ok with 3.3V input?

Cheers.

4

Should the arduino Rx be ok with 3.3V input?

Yes, it will.

5

I used a voltage divider to get the voltage down but no luck. Really confused as both the Bluetooth module and arduino work perfectly with hyper terminal but together they won't play ball.

Any other thoughts?

6

If this does not work, I have no other thoughts...

7

Thanks. I will give it a go and post back what I find.