Bluetooth SMD Module - RN-42

This module from Roving Networks is powerful, small, and very easy to use. This Bluetooth module is designed to replace serial cables. The Bluetooth****stack is completely encapsulated. The end user just sees serial characters being transmitted back and forth. Press the 'A' character from a terminal program on your computer and an 'A' will be pushed out the TX pin of the Bluetooth module.

The RN-42 is pin a compatible substitution for the RN-41. The primary difference between the RN-42 and RN-41 is that the RN-42 is a Class 2 device meaning its range is about 50 to 60 feet and correspondingly the power consumption is reduced.

The RN-42 is perfect for short range, battery powered applications. The RN-42 uses only 26uA in sleep mode while still being discoverable and connectable. Multiple user configurable power modes allow the user to dial in the lowest power profile for a given application.

Supporting multiple Bluetooth profiles such as SPP and HID and simple UART hardware interface, it is simple to integrate into an embedded system or simply connect to an existing device. The RN-42 is FCC and Bluetooth SIG certified making it a complete embedded Bluetooth solution.

  • Fully qualified Bluetooth module
  • FCC Certified
  • Fully configurable UART
  • UART Data rates up to 3Mbps
  • Over air data rate of 721kbps to 2.0Mbps
  • Low power sleep mode
  • Compatible with all Bluetooth products that support SPP
  • Includes support for BCSP, DUN, LAN, GAP SDP, RFCOMM, and L2CAP protocols
  • 3.3V operation
  • Status pin
  • Bluetooth Technology v2.0 compatible
  • Class 2 power output

Bluetooth SMD Module - RN-42 Product Help and Resources

Using the BlueSMiRF

September 16, 2013

How to get started using the BlueSMiRF and Bluetooth Mate Silvers.

Core Skill: Soldering

This skill defines how difficult the soldering is on a particular product. It might be a couple simple solder joints, or require special reflow tools.

3 Soldering

Skill Level: Competent - You will encounter surface mount components and basic SMD soldering techniques are required.
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Core Skill: Electrical Prototyping

If it requires power, you need to know how much, what all the pins do, and how to hook it up. You may need to reference datasheets, schematics, and know the ins and outs of electronics.

3 Electrical Prototyping

Skill Level: Competent - You will be required to reference a datasheet or schematic to know how to use a component. Your knowledge of a datasheet will only require basic features like power requirements, pinouts, or communications type. Also, you may need a power supply that?s greater than 12V or more than 1A worth of current.
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Looking for answers to technical questions?

We welcome your comments and suggestions below. However, if you are looking for solutions to technical questions please see our Technical Assistance page.

  • Bunk / about 12 years ago * / 5

    question deleted to protect intellectual property rights

    • S_Adolph / about 11 years ago / 4

      That does not matter - if it was disclosed, it is a disclosure, even if it was deleted.
      Acknowledging the disclosure with a deletion notice is pretty funny!

      • thebrit / about 10 years ago / 1

        Damn I all Kwang right now is toknowwhatthe question was.

  • Loopy / about 10 years ago / 2

    Is it possible to send data from the iPhone to a RN42 in HID mode without an apple chip? What mechanism can be used to send data to a HID device? AFAIK HID devices are usually input only devices.

    • thebrit / about 10 years ago / 1

      Yes absolutely however apple disables the on screen keyboard when an HIDdevice connects. Is this ok in your product?

      • tobs / about 9 years ago / 1

        I was wondering about the exact same thing. Is it possible to send data from the host (linux computer in my case) to the microcontroller attached to the RN42 in HID mode? Did you succeed with this? If so, could you share how you did this exactly? Would be highly appreciated.

  • Gerpus / about 10 years ago / 2

    Are you guys sure this module consumes 26 uA while still discoverable? I'm trying to figure out for how long will this module run on 2 AAA batteries (or one 3V coin battery) while only being discoverable (no communications or pairing necessary). My use case has to do with rf id only. I need an active tag visible from at least 10 meters by an Android mobile device. Thx!

    • Gerpus / about 10 years ago / 3

      Answering my own question here. Please correct the product description. "26uA consumption while still being discoverable" is incorrect. I just got the following message from Roving Networks support:

      "The module is not discoverable in deep sleep. The module can be put in a mode that toggles between deep-sleep (26uA) and discoverable (35mA). The duty cycle can be adjusted to trade off visibility and power consumption. About 3mA average is typical with 260uA still giving reasonable (10 sec) visibility."


  • Member #417563 / about 9 years ago / 1

    I have a rather urgent question.

    We've used the Rn41 Sparkfun BlueSmirf v4.77 for a while. Now, we purchased 10pcs. It turns out that the SW version on these are v6.15

    The problem is that the command S7,1 (7-bit mode) gives an error. That worked in v4.77

    Why is that? How do i simply downgrade the Firmware back to 4.77?

    Hoping for a fast answer since this is very, very urgent (as i mentioned before). We're shipping this unit to a customer abroad on Monday!!

  • Mariano / about 9 years ago / 1

    I see two analog inputs on this device. Can you configure the GPIO for extra analog inputs? I need 3 ADC's.

  • Member #491419 / about 9 years ago / 1

    I'm trying to pair two RN-42 using Arduino Mini Pro for a school project. I'm really lost. I'm trying to connect them together using the master/slave combination. Does anyone know of any tutorials that would help me? Or anything? Thank you!

    • Member #148178 / about 9 years ago / 1

      That video helped me out. Also, the data sheet and user manual above are fairly detailed.

  • Mariano / about 9 years ago / 1

    There are two analog inputs and there are also GPIO. Can the GPIO be configured as analog inputs also?


  • So am I correct in assuming powering this directly from a 3.6V Lipo will damage it?

    • Kamiquasi / about 9 years ago / 1

      That's a pretty good assumption. While 3.6V is already at the max for the module (see datasheet), Lipo batteries actually have a voltage range well above that (~4.15V) when they're fully charged and tend to linger around 3.7V for most of their discharge curve.

  • Member #243083 / about 9 years ago / 1

    Is can be possible use to sent data(not voice) from another devices(android phone or window pc) to iphone.

  • hi everyone i am using this module in one of my project to send data from RN42 module to PC after paring I am able to see COM3 and COM4 can any one tell me why there are 2 COM port. And this COM port is visible in device manager but not in terminal. why?

  • Member #453376 / about 9 years ago / 1

    If I have, let's say 4 of these chips transmitting at the same time and location, will the device receiving the transmission be able to distinguish each chip? Do each chip transmit in a unique id? can I configure it to do so?

  • Member #436126 / about 9 years ago / 1

    Hi Is there a breakout board for this or some simple way of connecting it to an Arduino Uno? Many thanks James

    • Kamiquasi / about 9 years ago / 1

      While not breakout boards per se, could these be a solution for you?
      Bluetooth Mate Silver
      Bluetooth Modem - BlueSMiRF Silver

      If you do need a full breakout, scroll up a few comments for a link to some on offer from another vendor. You may also be able to get away with soldering this to a protoboard yourself, but the irregular pitch of the module makes that a bit of a challenge.

  • Member #435788 / about 9 years ago / 1

    sir we are doing a delta robot project and we are using a rn 42 module ...and here it is not possible to read the input data from the android phone (using sketchy application) to the microcontroller using this bluetooth module wheather RN 41 satisfy our needs .. can u pls help us to solve this issue

    • The AirBoard / about 9 years ago / 1

      Thanks for your answer. I'll test with the RN41 and let you know.

  • The AirBoard / about 9 years ago / 1

    I want to remote program an Fio board with the RN42 Bluetooth module but I can't have the DTR signal driven to remotely reset the board. I pulled low pins UART_CTS, DCD (PIO3), DSR (PIO6) and CTS (PIO7). The only profile that seems to drive remote DTR & RTS is MDM SPP (the Roving networks datasheet states that profiles DUN should also drive them but I can't see that). But with the MDM SPP profile, the device is automatically recognized as a keyboard which prevents use of the terminal or the Arduino IDE. Can anybody help ?

  • Member #433028 / about 9 years ago / 1

    i have a doubt please help me out. i want to connect this chip to my mobile phone. so how do i connect? i want to use this chip to triger signal. say a button click. i.e like a button , when cliked uses this module to connect to my smart phone. how will this chip be usefull. please xplain me. wil be really useful for my project. regards, viswa s s

  • Member #425531 / about 10 years ago / 1

    can you use this module to recive audio from a cell phone? also can you slave them together so that you can send data to both of them with one connection? i would like to use two of these to create a piar of wireless earbuds and need some compact wireless solutions. any help is greatly appreciated.

  • satan's_soldier / about 10 years ago / 1

    Hi, I have been trying to use this module and I want to save power when I am not transmitting. Here is the user manual -

    Now My requirements are these 1. keep the module connected to my pc 2. transmit "Hello" to pc when a button pin 12 goes high on the arduino, this will happen by button press

    So when I am not transmitting, I want to be able to keep the device in sleep mode. The command for that is SW,8000 However my module is still consuming 25 miliamps when not transmitting. Has anyone tried this?

  • Member #40880 / about 10 years ago / 1

    Can I use this device to wirelessly receive audio from my iPad or Android Tablet?

  • HrvPav / about 10 years ago / 1

    Will this module work with a BlackBerry - more specifically, running OS6?

  • dizot / about 10 years ago / 1

    I just wanted to share my experience with using the RN42 and RN41 at high [115k+] data rates. It may apply to lower rates, but I haven't tested. These devices seem to disconnect from the BlueTooth host after communicating for a short period [in some cases less than 1 sec]. After some trial-and-error, I realized that the power supply needs decent bulk capacitance. I didn't test exhaustively for the optimal cap value, but bypassing power via a low-ESR 470uF capacitor totally stabilized my module. Now it works all of the time.

    Hope this saves someone else some aggravation.

    • Member #182792 / about 8 years ago / 1

      I believe I have solved this. The earlierst firmware revision I have for this device was dated in 2010 [using the breakout module from Sparkfun], and it did NOT exhibit this behavior. I added extra filter capacitors onto the board containing the module, similar to 10uF up/downstream capacitors on the Sparkfun module, and there was no change in behavior [so it's not filtering]. As it turns out, it is caused by the command mode processing and appears to be an RN-42 FIRMWARE BUG. To make the problem go away, disable command mode via "ST,0" and you should be able to transfer data without disconnects. It works for me. I would guess that you might have allowed 'command mode' filtering to time out when you did your filter capacitor testing, and that's why it 'worked' with the capacitor.

    • thebrit / about 10 years ago / 1

      Atypical RF Scenario me thinks, but greatthatyou highlight this.....

  • charlesfries / about 10 years ago / 1

    I am trying to make a pair of Bluetooth headphones that I can connect to my iPhone. Will this module work for my purpose?

    • thebrit / about 10 years ago / 1

      The 42 is data module. RN will launch an audio module very soon.

  • Mehrdad / about 10 years ago / 1

    Does anyone know where I can buy RN-42-APL (iPhone compatible version of RN-42) without having to go through MFi. I am just making a prototype and I won't be eligible to pass MFi business credit review right now. I just need one sample.

    • CodyCan / about 10 years ago / 1

      Unfortunately I don't believe you can purchase the RN-42-APL version without a MFi license. Even if you would get your hands on the RN-42-APL you would still need an authentication coprocessor from Apple and you are absolutely required to have an MFi license to purchase those.

  • LaserGecko / about 10 years ago / 1

    What would I need to add to this module to use it to control my telescope via the controller's RS-232 port? I'd like to use it with SkySafari instead of having to use the sketchy Android support for WiFi ad-hoc.

    • thebrit / about 10 years ago / 1

      Remember though that they also support 'softAP' mode. Which is basically point to point but infrastrucre mode. Roving already have solved this...

      • I think you are both talking about the wrong product. This is the bluetooth board. It sounds like you are discussing the RN-131 or RN-171

  • onaclov2000 / about 10 years ago / 1

    My latest project using one of these devices connected to and arduino, and communicating to an android phone:

  • Doov / about 10 years ago / 1

    Has anyone tried to configure the time delay between power on and discoverable? I'm finding that after powerup it takes about a minute using default settings for the device to actually be discoverable and a connection made.

    • Doov / about 10 years ago / 1

      FYI I changed this in about 2 seconds. Just send $$$, wait for the CMD, send ST,0, and then send ---. No more long wait times to connect.

  • Member #98966 / about 10 years ago * / 1

    Does this chip support A2DP or Audio? I'm working on a wireless audio project and would love to know if this would work!

    • thebrit / about 10 years ago / 1

      Rumor mill has it that a audio modules on its way. Roving intent to launch one very soon.

  • Member #231866 / about 11 years ago / 1

    Why post prices for 10+ and then limit it to 9 per customer? -.- Or is it only limited when stock is somewhat low?

  • trandi / about 11 years ago / 1

    Great product, I bought the cheaper, no-name version from eBay, but for a few dollars more I would have preferred this one !

    In any case, here's a nice example of usage:

    Basically making a simple Ikea night lamp remotely controllable by your Android phone ... pretty sleek !


  • andywh / about 11 years ago * / 1

    This is definitely a fantastic BT module to use. It pairs easily w/ Android, Windows Mobile, Windows..etc. Haven't tried it w/ an Apple product though.

    If anyone needs RN-42 breakout boards, a board that supports a PIC24F micro along w/ the RN-42, or vehicle OBDII Bluetooth interface modules, check out the ones I've designed here: OBD-II Bluetooth Adapters The adapters are open source, hackable, and Altium sources are available on the linked page!

  • Member #272175 / about 11 years ago / 1

    Have anyone tried to connect this module with an iPhone? would it work? I've read that bluetooth at iPhone is very limited.

    • thebrit / about 10 years ago / 1

      The RN-42apl is the device you want but you will need to be a member of apple's MFI program before you can procure one.

    • thebrit / about 11 years ago / 1

      goto the Roving site and look at this:

    • Maxim / about 11 years ago / 1

      I'm puzzled as well. On the Roving Networks site it says that the unit "Supports Bluetooth data link to iPhone/iPad/iPod Touch", but the UM doesn't make any reference to that.

      In my case i'd like to be able to use the RN42 to tether with an iPhone so my device can access the internet.

  • EliTheIceMan / about 11 years ago / 1

    This works great with Google App Inventor. I have made several projects controllable from my Android (even using the accelerometer). I'm just in the process of trying to speed up the connection process. Every time I open the app I have to attempt to connect and sometimes it takes several attempts-not sure if phone or module.

  • KLD / about 11 years ago / 1

    In the item description it says "UART Data rates up to 3Mbps" however in the data sheet "Roving Networks Users Manual" there is no mentioning of how to accomplish this, only limits up to 921K is available! Can you explain this please?

  • OlegM / about 11 years ago * / 1

    I wrote a short post showing how to check this module using Android phone, please take a look here ->

    • snacker / about 11 years ago / 1

      Thanks for posting this.
      It was actually helpful to see how simply it can be used!

  • Hyperian / about 11 years ago / 1

    is it possible for this to be connected to bluetooth on a phone so the phone can transmit data back and forth?

    • Jonathon Cox / about 11 years ago / 1

      You can also use the BluetoothChat example in the Android SDK to connect to the module. Just change the UUID like this:
      private static final UUID MY_UUID = UUID.fromString("00001101-0000-1000-8000-00805F9B34FB");

    • Julio Terra / about 11 years ago / 1

      It depends on the phone. You can use Amarino to connect an arduino to an android phone using bluetooth in SPP mode. Not possible with the iPhone though, as far as I know.

      • thebrit / about 11 years ago / 1

        It is possible with the RN42 (and RN41) but Apple requires you add an apple authentication chip to your widget. RN modules can handle direct communication with the auth chip but Apple requires you buy the auth chip directly with them.

        Roving explains the procedure very well via the phone.

  • dainita / about 11 years ago / 1

    este producto me interesa cuanto seria de 6 piezas en pesos mexicanos y cuanto tiempo tardan en llegar a mexico y se paga envio

    • SomeGuy123 / about 11 years ago * / 1

      I'm going to do my best with Google translate here.
      Sparkfun hace envios internacionales. Ir al su cart y haga clic en "Checkout". Los gastos de envio se debe mostrar que despues de agregar una direccion de envio.
      Vaya aqui para seleccionar su moneda.
      En contacto con para obtener más información.

  • Jon Andrews / about 11 years ago / 1

    Does anybody know - or had experience, in using two of these modules together in a slave/master combination with two separate microcontrollers?
    i.e - One arduino passing some serial data to another arduino.
    The above manual seems to indicate to me that this is possible, but I'm keen to know if any of you guys has had any joy doing this?
    Thanks in advance - Replies appreciated!

    • Member #211675 / about 11 years ago / 1

      Yes, I did it successfully with these modules (RN-42 / RN-41) to sync two pace clocks together over a large range in a master / slave configuration (about 75 meters indoors using the RN-41). They're still working great!

      The remote module's address can be set in the configuration mode. If you want persistently paired modules this only needs to be done once and can be done with auto-connect pin settings or in the configuration mode (the latter is easier to understand).

      If you want the host microcontroller to initiate pairing with multiple modules (only one-at-a-time is possible), it either needs to 1) enter the local module's command mode and choose a different remote address or 2)turn off all other nearby slave modules except the target remote module, and then use the auto-connect mode.

      Depending on the application, one might be better than the other, although in my experience the settings done in the configuration mode are much simpler than the procedures automatically carried out by the module when IO pins are flipped (like auto-connect mode, for example).

      • Member #491419 / about 9 years ago / 1

        I'm trying to pair two RN-42 using Arduino Mini Pro for a school project. I'm really lost. I'm trying to connect them together using the master/slave combination. Do you know of any tutorials that would help me?

  • norinori / about 11 years ago * / 1

    I had trouble finding information about using this module with osx and processing, so now that I have a working setup, I thought I would post my code.
    1) add RN42-0321 SPP to your bluetooth setup
    2) need to "edit serial ports" to activate it.
    3) Once you set that up, you can use this processing program to automatically activate your bluetooth connection and set command mode.
    // Processing program for connecting and getting data from RN-42
    // Steps:
    // 1) Turn on RN-42
    // 2) Start program within 60 seconds
    import processing.serial.*;
    int lf = 10; // Linefeed in ASCII
    String myString = null;
    Serial myPort; // Create object from Serial class
    int val; // Data received from the serial port
    boolean init = false;
    void setup()
    size(400, 400);
    String[] ports = Serial.list();
    String portName = "";
    for (int i= 0;i 0) {
    myString = myPort.readStringUntil(lf);
    if (myString != null) {
    void keyPressed() {if (key == 'd') {

  • Member #227689 / about 11 years ago / 1

    can you please help me by telling me where can i find how to connect the mobile phone with the rn42??

    • thebrit / about 11 years ago / 1

      what mobile phone?.... An Apple phone? Apple requires YOU to add an Apple authentication chip to your product before it will show up in the BT list unless it is a headset or keyboard.

  • Member #211675 / about 11 years ago / 1

    If anyone needs a PCB layout, gerber files, connection help, or design tips for one of these RN-42 / RN-41 modules, check out our project website by googling "ece 4760 time system". We bought the modules here at Sparkfun and used them to make an Android-controlled programmable pace clock.

  • erich81 / about 12 years ago / 1

    any plans to get these added to the Eagle library?

    • thebrit / about 11 years ago / 1

      According to RN, they are being removed from the module to avoid confusion.

  • S_Adolph / about 12 years ago / 1

    Hi everyone.
    I'm laying out a board to carry the RN42. The RN41 has 3 extra pads where the antenna would have been connected/grounded. Are they an issue for RN42?
    Does anyone have an updated eagle device for the RN42?

  • Legolas8911 / about 12 years ago / 1

    Hi guys
    I have a question. Can i use this with arduino for connecting my phone to it? I want to trigger a relay when my phone comes in the range of the bluetooth module and connects to it.
    And another question, how can I wire this module, because it seems a little too small :)
    Thanks in advance

    • Beto / about 11 years ago / 1

      yes you can. I am controlling 2 of my robots with my Android phone using SPP. One of the robots is here: I'll be updating the forum with a video detailing everything. Yes you can saughter directly onto it, but you need a steady hand and one of those alligator-clip based helping hands from radio shack to hold/line both the wire and board together.

  • Jay18g / about 12 years ago / 1

    Hey guys. Once you link another bluetooth device to the Rn42 radio can you toggle the GPIO pins on the RN42 via the other linked device?

  • Jeff Rowberg / about 12 years ago / 1

    I would absolutely love to have the resources and instructions necessary to use this exact module with a HID profile for a mouse/keyboard device. It seems everything out there is SPP-only, designed only for serial communication...unless I'm missing something. I've had no luck so far finding a Bluetooth module with keyboard/mouse support available in small quantities to hobbyists.

    • WimL / about 12 years ago / 2

      I agree, it's really frustrating how limited the Roving modules appear to be. Despite the sparkfun description text there doesn't seem to be any way to support HID, or really anything other than SPP or DUN. There are hints in the manual that you could flash the module with different firmware to enable HCI on the serial port, but neither SF nor Roving's website have any more information on this.

      • Julio Terra / about 11 years ago / 1

        Has anyone ever figured out how to use these bluetooth modules in HID mode? Is it really possible to do so?

  • This is a great module, good to see SFE carrying it. Now if only BLE would hurry up and mature!

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