RN-41 SM interfacing questions

Hi Guys,

I just recently bought an RN-41 SM (http://www.rovingnetworks.com/documents/rn-41sm-ds.pdf) bluetooth module for my Arduino UNO.

I actually intended to use it with Arduino UNO but I have a problem communicating with it. Although I can enter the CMD mode of the RN-41 via Bluetooth, I cannot pass the data from RN-41 SM to Arduino.

I know it’s not my code for Arduino because it is working with USB as serial. If the RN-41 would work as just a wireless serial port, it should also work the same.

Here are my connections: I used the Header B so I disconnected the R6 and R8 resistors. Then connected the TX of RN-41 SM to RX of Arduino and RX of RN-41 SM to TX of Arduino. The VCC is connected to 5V supply from Arduino UNO board and GND to GND of Arduino. CTS tied to RTS. Forced the Baud rate to 9600 using the jumper.

Am I missing something with the connections or something? Does anyone already tried working with this BT module? Your help is very much appreciated.

Thanks, Francis


While waiting for answers, I am continuously debugging my setup.

Since my Arduino UNO is not responding to data I sent from my PC to Arduino via BT, I wrote a code that will do the other way. (this time from Arduino to PC via BT)
The code is will just continuously send data every second while I am monitoring via my hyperterminal.

What I found out is that I can receive the data sent by Arduino to my PC but it seems my Arduino cannot receive what I sent from my PC.

Any ideas about this?
Is there a problem with my Arduino Tx pin?

I got the same problem and i can't figure out what is happening.. When i try through windows i can't send anything but when i try from my MacBook Pro i send a value 10 times in a raw and then sometimes arduino recieves it. Why is that?

Hi lperissis,

Try to remove R2 from RN-41 SM and short the pins together. This resistor becomes a high pull-up when you connect the Tx pin of RN-41 to Rx pin of UNO

By the way, are you using the same set as mine? (UNO + RN-41 SM)

yes i do. i will try removing the resistor and see if this helps at all. I also found out this tutorial and says that your bluetooth module has two com ports one for outgoing and one incoming. Did this , resistastor removement helped you at all?


Yes. It does help. Don't forget to short the pins after removing the resistor.

If you were able to connect to BT module from PC then this solution should work.

But if you were not able to establish connection between PC and BT module then it is another issue/problem.