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RFM22B-S2 SMD Wireless Transceiver - 434MHz

The RFM22B is a low-cost ISM FSK transceiver module which offers communication at 433MHz ISM and adjustable output power of up to +20 dBm. The wide operating voltage range of 1.8–3.6 V and low current consumption makes the RFM22B an ideal solution for battery powered applications.

Communication with the RFM22B is achieved via a standard 4-wire SPI interface. Three configurable general purpose I/Os are also available, the use of which can be tailored towards the needs of your project. A host of other features are also available including an 8-bit ADC, temperature sensor, RX and TX FIFOs, and low-battery detection. See the datasheet below for a complete description of every register and command.

The module comes in a 16-pin, 16 x 16mm, SMD package, with pins spaced by 2mm. Look for a breakout board coming soon!

Note: These modules are 433MHz and Rev3.0.

  • Frequency Range: 433MHz ISM
  • Sensitivity = -121 dBm
  • Output power range: +20 dBm Max
  • Data Rate = 0.123 to 256 kbps
  • FSK, GFSK, and OOK modulation
  • Power Supply = 1.8 to 3.6 V
  • Ultra low power shutdown mode
  • Digital RSSI
  • Wake-up timer
  • Auto-frequency calibration (AFC)
  • Power-on-reset (POR)
  • Antenna diversity and TR switch control
  • Configurable packet handler
  • Preamble detector
  • TX and RX 64 byte FIFOs
  • Low battery detector
  • Temperature sensor and 8-bit ADC
  • –40 to +85 °C temperature range
  • Integrated voltage regulators
  • Frequency hopping capability
  • On-chip crystal tuning
  • 16 x 16mm (0.63 x 0.63 in)

RFM22B-S2 SMD Wireless Transceiver - 434MHz Product Help and Resources

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: Programming

If a board needs code or communicates somehow, you're going to need to know how to program or interface with it. The programming skill is all about communication and code.

2 Programming

Skill Level: Rookie - You will need a better fundamental understand of what code is, and how it works. You will be using beginner-level software and development tools like Arduino. You will be dealing directly with code, but numerous examples and libraries are available. Sensors or shields will communicate with serial or TTL.
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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.

2 Electrical Prototyping

Skill Level: Rookie - You may be required to know a bit more about the component, such as orientation, or how to hook it up, in addition to power requirements. You will need to understand polarized components.
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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.

  • can anyone help with a straight forward implementation using arduino uno and arduino ide ?

  • This device now has a RF22S chip on it, and reading the device type register shows version 6. There are e new register datasheets corresponding to this version at:

    SI4430/31/32 Register Descriptions

    FIFO mode, Direct mode, and Packet Handler Operation

    (edited to fix link formatting)

  • Why is 14-PIN DIP listed as a feature when sparkfun is selling the SMD package?

  • Anyone have interests in long range low power transceiver modules? The RF distance is much longer.

  • Any chance SFE could stock the HopeRF RFM69HW modules? Whilst not a RFM22B replacement per se they are the "next generation" of modules. They look pretty good and can be hard to find.

  • I managed to brick an openLRS RF module - I am going to replace it with one of these and see what happens.

  • Using full power, 100mW, at 434Mhz, the correct 434Mhz tuned module, 1kbps packets, 1/4 wave vertical whips, line of sight between hilltops is at least 40kM, maybe a few kM more.

    In a Forrest or urban area, with the modules at ground level, the range is around 300M.

  • Does anyone know if this is a good radio tech module to base a new development on. I am looking at wireless sensor networks for heating control and other odd and ends projects. I like the possibilities of mesh networks.

  • I bought 2 of these. One is connected to arduino Uno and acts as a reciever the other connects to arduino nano and acts as transmitter. The problem is that they can't communicate with each other using the 3.3V coming from the arduinos. Only when connecting an external 3.3V for any of the RFM22 I get great communication. Is that makes sense??

    • The Arduino Nano uses the FTDI chip for its 3.3V supply. Unfortunately the FTDI chip can only supply about 50mA, which probably isn't enough to successfully run the RFM22. Use a beefier external 3.3V supply for the Nano. The Uno has a "real" 3.3V regulator and doesn't have this problem.

  • Would it be possible to set these up so that one unit transmits and multiple other units receive the same message? As in, without having to send the message multiple times.

  • RTFM22-S2

  • POSSIBLE BUG : If a zero data length packet is received with a CRC error, no subsequent valid packets can be received until the device is reset via power recycle (maybe with a soft reset.) I had attempted to use zero data length packets for ACK/NAK responses and into this problem. Once I changed them to one data byte packets all was well - going to contact HopeRF and SiLabs.

    Overall, this is a great module and I highly recommend it!

  • Check out my little Data Logger (using an RFM22B of course):

    Facebook: example

    YouTube example

  • Question: from reading the comments, it looks like this only works on the 433mhz band. So, Is there any way to get more than one of these operating at the same time?

    • 5 months in the making.... the answer is yes, the carrier frequency, baud rate, frequency deviation are all programmable, as well as programable headers for different data packets. You could have several operating around each other all at once.

  • I'm slightly curious how these things are legal in the US seeing as how they can be tuned anywhere from 260-960Mhz. Is it exempt from FCC rules or something?

    The only legal way I know of to operate this thing outside of its original frequency is with an amateur radio licence and then only on 70cm and 23cm bands. I believe to operate on the ISM bands it would have to be approved by the FCC.

    • You are right. The 260-470MHz unlicensed band in the US is where these operate and the FCC specifically prohibits periodic data transmission. The one exception is if you transmit less than 300mSec every 10sec. But even then, you are limited to like 5dBm into a 1/4 wave monopole. These are not legal in the US, period unless you have a license. If you are a hobbyist, you wont have a problem, but there is no way you will be able to put this into a product you intend to sell. 902-928, 2.4GHz, and 5.8GHz are the only options for unlicensed data in the US that I know of.

      You can follow my blog for topics like this one at: www.stevetherfguy.com.

    • the two bands in which this operates is located in the 70cm and 33cm band. both of these are secondary allocations for the amateur operators. the 260Mhz appears to be allocated for "fixed, mobile, and mobile satellite" uses (http://www.ntia.doc.gov/files/ntia/publications/2003-allochrt.pdf).

      personally, this is a great little device - and since i am a ham operator i plan to use this within frequency that i can legally use in a fun science project with the boys. a small series of stations that collect weather information and xmit back to the "mother ship".

      HOWEVER, it appears that on page 3 of this document: http://transition.fcc.gov/Bureaus/Engineering_Technology/Documents/bulletins/oet63/oet63rev.pdf that

      "Hobbyists, inventors and other parties that design and build Part 15 transmitters with no intention of ever marketing them may construct and operate up to five such transmitters for their own personal use without having to obtain FCC equipment authorization."

  • I am thinking about putting one of these in a key fob, but my concern is the antenna. Any ideas if this can work with such a small antenna being coiled in such a small enclosure?

  • So let me ask a dumb question. What do you call that surface mount part, which accepts a wire which acts as the antenna for the 433MHz? I've been doing all kinds of searches for wire connector, receptacle, etc, but I can't seem to find what I'm looking for.

    I want to be able to connect and disconnect the antenna from the board.

    Thanks for any suggestions.

    • I hope you found what you were looking for before my reply here, but even if you did this may help someone else. The part you are referring to is a board edge, end launch connector like this http://www.digikey.com/product-detail/en/CONREVSMA003.031/CONREVSMA003.031-ND/340146 this one is a rp-sma connector (probably the kind you want). You'll need a board of some kind to mount it to. It may be possible to use a proto board, just make sure you're rf connections are good or you'll have lots of loss.

  • Can anyone tell me what this (the -S2) version weighs in hundreds of a gram? I wish to use this in a very weight sensitive application. I wrote the company and asked but they don't seem to want to answer. Thanks!

    • Mine, purchased Mar 2011, weighed .70-.71 g fresh out of the bag

      If you really need to, you should be able to shave a few .01s off that with a jewelers file

  • Hi, I'm considering to buy this chip. But I have a question: is this chip packaged already? I mean if it's in this form, what should I do to attach my wire on this chip? Thank you very much!

  • Going through the sample code, in the init_RFM22 function it writes to the register 0x58 (and some others similarly), but this register seems to be reserved (according to http://www.hoperf.com/upload/rf/AN440.pdf). Am I reading the wrong document or is there some other reason for this? Thanks!

  • I'm expecting to buy this device but I don't understand If this IC could be used as Transmitter and Receiver at once, well as for example first sends data and it can wait for a response. I'm newbie sry for the question.

    • Hi Guys I want to buy 2 of these for my project and hope to get some confirmation from you smart people:-) will I be able to use a small GPS unit and send lats and longs over this RF unit via a 328p lets say ever 10min?
      is there breakout boards available for this units?
      Thanx in advance

  • I'm a bit irked to hear this won't work out of the box for the 915 Mhz band as well. Of course I read the comments after placing an order for two :| Would have been nice if the product description explicitly said that.
    That said, it would be great if you carried the 915-tuned module.

  • Hi has any one of you, used the RFM22B-S2 SMD Wireless Transceiver as a Aircraft Down Locator Beacon on 434 MHz. I'd be interested to learn if it is feasable or not? Is there a circuit of a modulator floating around that could be used as a CW ID'er?
    Well, Thank you for your time and information. Richard T.

  • Does this one have an RF switch (SPDT) on the antenna line, after the matching network? It seems like it does from the photos but the diagram on page 12 of the manual doesn't show one. Anyone know?
    Anyone know where you can get the 915MHz ones in North America?

    • Actually it's an AMP the RM23B doesn't have that chip, does not require RX_ANT and TX_ANT inputs and hax max transmit power of 13dBm. This one requires use of RX_ANT and TX_ANT pins (which go directly to that small chip) and transmits at a max of 20dBm -> that chip must be an amp

  • Just wondering if SF is offering the 915MHz version?
    You cannot simply adjust register values to get a different frequency, the cap, inductors, and resistors in the matching network must be changed as well.

  • Hello.
    Can you make module or breakout card with Silabs SI1000 ?
    Incorporating C8051F930 SI4432 on same chip, should be smaller and have greater potential.

    • I second that.
      I have plans to use it in my project, so a breakout board with SI1000 would be nice to have.

  • When do you guys expect this to be back in stock? I'd really like to use this for a project but you seem to be the only US distributor.

  • Um...wow. This item covers the amateur 440,220 and 900mhz allocations (here in the US at least) That is major coolness.

  • I assume I can place this on a board where the antenna line goes out to an SMA connector for any antenna I want. Let's assume I connect a standard quarter wave monopole (ducky) antenna to this connector and crank it up to full power (+20dBm). Assuming line of sight, what does this (order of magnitude) translate to in terms of range? <br />
    <br />
    A comparable device is the Atmel AT86RF212 at 900MHz. The Atmel part has a max tx power of +10dBm and has receive sensitivity down to -110dBm. Meshnetics claims they verified its functionality at 6km (assuming a directional antenna was used). <br />
    <br />
    Can we extrapolate that this device can do better than that based strictly on tx power, receive sensitivity and band (900MHz)?

    • As Dan said, your milage WILL vary, but for anecdotal reference:
      I used these in a project transmitting a small data packet twice a second. The basics were:
      434 MHz, with 2.4 kbps data rate, GFSK modulation, 45 kHz frequency deviation, +20 dBm output power and these antennae:
      With the transmitters sitting on my desk, I got the receiver out the door of the office and about 200 m up the road before the signal dropped out (industrial area). That was more than sufficient for the project so I didn't experiment much further. You'd probably do 50 to 100 % better with a 14 cm piece of wire on both ends for antennae, but my project was space-constrained.
      Higher over-the-air data rates will reduce power consumption but would probably reduce the range - by how much I couldn't guess.
      SI Labs has an Excel spreadsheet that helps you work out a lot of the register settings. See the EZRadioPro Register Calculator under Design Tools:
      The radios I got were revision B1, but I got them direct from Hope RF before SparkFun started carrying them. I'm 90% sure SparkFun has revision B1 units. You can figure it out by reading register 0x01, which will return 0x06 in revision B1 units.

    • Your milage WILL vary, depending on everything in your environment. Really have to just build and test it to get real-world experience.<br />
      <br />
      When you talk about a radio link, you have to take into consideration transmitter power, antenna gain or loss (ususally loss), propagation loss (stuff in the way), rx antenna gain or loss, and then reciever sensitivity. This is the link equation, and adds up to what people think of 'distance'. <br />
      <br />
      Calculating it gets you close, often it's just easier to do your best, and find out what you end up with.<br />
      <br />
      So if you want more range, power is a minor piece. Often getting a resonant high gain antenna on both ends, and pointing them at each other with nothing inbetween will exceed manufactuers specs.<br />
      <br />
      -Dan N7NMD<br />

  • Either I am missing it, or one of the top questions isn't answered - how far apart will it reliably communicate? I understand there are factors and caveats; inside a shielded warehouse with line of site is going to do much better than outside with buildings and trees in the way. Most of the applications suggested seem to imply the range is fairly short.

    • I put a SMA connector and dipole antenna on a 915MHz unit and got about 150m through an urban environment (through houses and care etc.) at 150kbps.

  • Will you only be selling the 434Mhz version?

    • The module is adjustable in software from 260MHz to 960MHz. Have a look at the datasheet on pages 21-22.

      • Yes, that's what the datasheet says. However, when we got some of these modules, there were several frequency options printed on the silkscreen of the PCB, and "434MHz" was marked. This didn't make sense to me - has anyone tried using these modules at anything other than the 434MHz band?

        • Yes, you can transmit and receive anything between 260MHz and 960MHz. That being said, there is a filter in place that will probably significantly limit your range outside of its intended band of operation.

          Even at something like 550MHz, I have these things about 30 feet apart (with a couple of walls), and some random wire antenna of improper length, and they work fine using the RF22 Library's datagram server/client. I see an RSSI of 125-130. No errors.

          The 550MHz setting is seeing much better SNR than the 433MHz setting, so I suspect these filters aren't that tight.

        • The transceiver chip the unit is based on (the SI4432) will do the full frequency range, but I'm pretty sure the other components on the board (antenna matching components) are tuned for the 433 MHz band.

          • Can somebody at SFE confirm this? I would really like to use this system at 915 MHz. If it is tuned for 433 MHz output, then what is the output power at the other bands?

            • John:

              Can somebody at SFE confirm this? I would really like to use this system at 915 MHz. If it is tuned for 433 MHz output, then what is the output power at the other bands?
              Any answer to this? Can you use a different frequency?

              • I'm interested in confirmation on the frequency, too.

                • I'm using these units in a design right now and can confirm the physical components on the module are tuned based on the frequency indicated on the silkscreen. You cannot adjust a 433MHz module for 900MHz through software.
                  If you want 900 or 815MHz units, contact HopeRF directly, they will sell small volumes (like 2 or 5) if you ask really nicely.

  • A slight confusion. Desc. says a max output power of +17 dbm, while the Features says +20 dbm

  • We are currently waiting for stock on these. You can backorder them for now and they will ship as soon as we get them in. Thanks!

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Haven't used it yet

Nice board. I have been tied up on another project and have not used this yet. Once I do use it I will give a report. I must say the folks at Sparkfun are the best.