Designing an RF transceiver

[William Dillon] is finishing up his degree. His final project as a student was to design an RF transceiver. He decided to work with the Microchip MRF49XA, which runs around $3 but will cost you $20 if you want it in a ready-to-use module. He didn’t find a lot of info on the Internet about communicating with these chips so he’s shared his design, code, and board files. If you’re ever wanted to delve into RF design this is a good primer. [William] talks about building around the example circuit from the datasheet but also includes a discussion of the calculations he made in working with the 434 MHz band, and an AVR-based library for using his module.

Comments

  1. Jared says:

    The MRF49XA is used in the Radica Puppy Tweets toy. You get two of these MRF49XA modules, one integrated into a USB dongle. I haven’t yet got to hacking these myself, so I have no idea how easy it is to hack these, but it can’t be rocket science. Go to the FCC OET license site (https://fjallfoss.fcc.gov/oetcf/eas/reports/GenericSearch.cfm) and look up FCC IDs “PIY T7004D1″ and “PIY T7004T1″. In the details, there’s even full circuit diagrams!

  2. Brian says:

    Huzza! I am making a wireless engine monitor and designed in this part for the wireless…this will help a lot!

  3. hpux735 says:

    @Jared

    Great find. There are several neat things about this. The first is that the design company is obviously using Altium schematic capture. The second is that they either use, or thought they may want to use, the direct interface to the frequency-shift-keying (FSK) pins. These are FSK and DCLK. This is an option if you want to use a higher bit rate, or if you want more control over packet synchronization. If you wanted to integrate this into your own project, you’d need to customize the schematic on my design for the 915 Mhz balun, and some changes to the code. Also, you’d need to figure out what bitrate and packet structure they’re using.

  4. Pete says:

    $6.67 for the RFM12B

    http://shop.moderndevice.com/products/rfm12b-radio

    This company even sells the RF transceiver embedded with microcontroller with code: $22.50

    http://shop.moderndevice.com/products/jeenode-kit

    Just bought some myself, so can’t vouch for performance, yet.

  5. hpux735 says:

    @Pete

    There’s a lot that can be done with quantity and the magic of outsourced labor. I added up the parts alone in single (or 10 for passives) unit quantities from Digikey and it came out to $5.73 w/o the PCB. Keep in mind that they also don’t use a package for the IC, opting instead for the cheaper epoxy blob.

    It’s very interesting to me, however, that the datasheet doesn’t give really any information about how to use it. When you find the programming guide, it’s obvious that this is likely made from the same IC. If that is the case, the library should be useful for those as well. There is some precedent for this, SILabs has a chip that is identical: http://www.silabs.com/products/wireless/EZRadio/Pages/Si442021.aspx

  6. Pete says:

    @ hpux735

    Here’s the programming guide via sparkfun:

    http://www.sparkfun.com/datasheets/Wireless/General/RF12B_code.pdf

    Here’s a link for the RFM12B uC code, geared arduino:

    http://jeelabs.net/projects/cafe/wiki/RF12

  7. hpux735 says:

    Assuming that they are compatible (and I think at this point it’s a safe assumption) then this library may also work:

    http://www.das-labor.org/wiki/RFM12_library/en

    ..from the sparkfun website

  8. polymorph says:

    hmm, this is going to be useful for my augmented reality paintball helmet.

    something about the cables on the left reminds me of the rainbow flag…

  9. George Johnson says:

    Oh yeah, this one is going to take some time to absorb….

  10. i always love seeing RF circuits :)

  11. strider_mt2k says:

    RF rules.

    -And I love seeing terms from my active ham days.

    FSK indeed! :D

  12. chamnan says:

    I can only say one word it the best.

  13. Dharmendra singh says:

    radio frequency hack

  14. John says:

    Hello,

    I am attempting to develop code for two RF transceivers to transmit data through a PIC16F877A micrcontroller. I am a first time user of both and not very familiar with programming in general. Can anyone offer some advice/assistance?

Leave a Reply

Fill in your details below or click an icon to log in:

WordPress.com Logo

You are commenting using your WordPress.com account. Log Out / Change )

Twitter picture

You are commenting using your Twitter account. Log Out / Change )

Facebook photo

You are commenting using your Facebook account. Log Out / Change )

Google+ photo

You are commenting using your Google+ account. Log Out / Change )

Connecting to %s

Follow

Get every new post delivered to your Inbox.

Join 96,376 other followers