Introducing the SM1000 Smart Mic

For the last few months Rick Barnich KA8BMA and I have been working on the SM1000, a embedded hardware product that allows you to run FreeDV without a PC. Just plug it into your SSB or FM radio, and you now have Digital Voice (DV). It’s based on a STM32F4 micro-controller, has a built in microphone, speaker amplifier, and transformer isolated interfaces to your radio. It’s just 80 x 100mm, and can be held in you hand and used like a regular PTT microphone, or sit near your radio in a small box form factor. The SM1000 will be in production later in 2014 and will retail for US$195.

Here is a block diagram of the SM1000 (click for larger version):

The whole design is open hardware (TAPR license). It will run an embedded version of FreeDV which is also 100% open source. You can forget about proprietary, expensive DV modes from other vendors that force you to use their hardware and make it illegal for you to experiment. Open source is the future of Digital Voice.

The schematic, PCB and other design files can be found in SmartMic SVN. The software is taking shape in the stm32 part of Codec 2 SVN.

The SM1000 has a RJ45 and 3.5mm sockets to interface to your radio, including a little patch panel to configure the RJ45 wiring. As it’s hand held and operates from 6-12V it could even run with low cost FM HTs, as an external mic.

We would welcome a review of the schematic and PCB design. Suggestions are welcome, but contributions much more so! Many hardware and software tasks are available for volunteers who are interested in contributing to the free and open future of Digital Voice. Rick Barnich KA8BMA is a recently retired engineer who is a veteran of over 100 PCB designs. He has done a fantastic job at schematic entry, sourcing parts, analog and digital design, and PCB layout – and he is having a great time in the process!

Rick and I are currently wrapping up the schematic and PCB design, and will be building up prototypes and various pieces of software over the next few months. Most of the analog design has been prototyped, Codec 2 is running on the micro-controller, but the modem still needs some work to reduce memory use. Lots of work required for the user interface, integration, and general micro-controller software.

81 thoughts on “Introducing the SM1000 Smart Mic”

  1. Mmmm, try *that* with D-Star.

    One question though, I see mention of a speaker jack, presumably for headphones. Have you considered a microphone and external PTT jack? I normally prefer a headset and a separate hand-held PTT, since I might be holding a clip board (and the PTT) with one hand, and writing down things with the other.

    It’d also make the device a useful and universal break-out box for plugging a conventional computer headset into a myriad of radios. (RF problems not withstanding.)

    1. Well lets see. It has an external mic jack, the PTT jack is an output intended to switch the radio. The internal PTT switch contacts would be easy to access if use of say a foot switch was reqd. Real estate along the board edges is also kind of tight….

      1. An alternative design:

        Have the microphone, speaker, PTT button connections on a header.

        So the main board would carry the MCU, power supply (a small 9V battery for example) and radio connections, a daughter board would have the speaker, microphone and PTT.

        The speaker/microphone/PTT can be a module that is swapped out for another with connectors if the user wishes.

  2. Very desirable or a Rasberry Pie style box in the Mic line. For Mobile/backpack HF we need.

    1. Actually I think we will build rigs into the uC next. It’s just a few more MIPs to move the radios into software.

  3. I want one too!!!

    Great. From the beginning of the codec2 soft that I expect hardware use, this are a great news.

  4. Great to see this idea that you talked about a year ago coming to fruition!

    Any chance of a demo model before Friedrichshafen?

    Perhaps you could start taking pre-orders there?

    I’m assuming this is aimed at HF rigs but you mentioned HTTs so maybe VHF/UHF as well?

    Looking forward to hearing one of these “in action”.

    73 Ed VK2JI / DD5LP.

    1. Sorry, not in time for Friedrichshafen. Yes with a viable Codec 2 FM mode it could run on UHF/VHF HTs. There has been a lot of talk about such a mode on the lists, but alas no code as yet.



  5. Can’t this be done cheaper though as a standalone device, just using a Raspberry Pi etc?

    73 G1KQH

    1. Hmm, that might be a good idea. Would let us gauge the interest and help scope and fund the initial production run.

  6. Hi David and all,


    How about a piggyback or mod so it can talk over the local ethernet? i.e.- allow it to interwork with the various stuff on the web. ip telephones, asterisk, etc. Maybe just a way to connect it to a local Beagle bone black or equiv. and then onto the internet?


    1. Hi John,

      The uC chip we are currently using actually has Ethernet hardware but we are short on real estate for the connectors. If you are keen on writing software for Ethernet support we could break out the uC pins for Ethernet to solder-able pads.

      Alternatively USB can be used to bridge to a Host.

      – David

  7. Hi David

    This sounds identical to an email request I sent to you about two plus years ago regarding the request for a stand-alone unit.

    Do not remember getting much feedback .

    Great idea and already see it being posted all over the net .Regards

    Bradley ZS5BG

    1. Hi Bradley,

      It’s been a common request/idea from many people for some time now.



  8. David,

    This is a fabulous idea. I heard about it on the VK_SOTA mailing list and is just the thing that may make DV practical for those of us who enjoy mountain top radio.

    I don’t think I’m qualified to review your schematic and layout (and compliments to you and Rick on the schematic and board – one of the clearest schematics I’ve seen in a while), I’d offer the following ideas for consideration:
    – The current board is going to be fairly large in a housing I suspect that may not make it too practical to hold up to ones mouth. It would make a nice interface box though between a conventional mic and a rig. I also note that it requires external power which would mean an additional wire I guess.
    – From the perspective of a portable operator, it would be greatly desirable to have a truly compact – single wire solution. I suspect this may be possible if you:
    1) remove the non-essentials (such as separate jacks for external mic, speaker etc). Does the uP have an adequate internal oscillator rather than using an external crystal? Do you really need isolation transformers to the rig if it’s battery powered with no potential ground loops ?
    2) re-layout PCB placing components on both sides (obviously using SMT as much as possible); re-purpose the VDD plane to carry signal traces to reduce the board area as far as possible; replace the patch header with just 0.1″ pads for solder jumper config; shape the PCB to fit a standard mic housing with the RJ45 at the end. Perhaps get a standard mic that has a PCB in it (e.g Yaesu MH-31; use the existing mic board outline as the basis of your design)and source the housings as spare parts from that company.
    3) Fit the PTT switch onto the board edge to match the mic housing as per a standard mic
    4) Use a speaker/mic model so that the speaker is in the housing too (with optional ear-piece jack maybe)
    5) Look at powering internally – most rigs produce about 8V at 10mA, but I suspect you need more power than that for the uP. Depending on the ability to use power down uP modes, is it possible to power this from a super cap charged from the 8v/10mA supply (i.e. can you get average power down to 80mW ?). If not, maybe look at a small rechargeable battery charged from the USB port (there’s good Li ion charger chips available in SMT that are designed to charge from USB).

    I’ll continue to watch this project with interest!

    I agree with an earlier suggestion that helping fund via KickStarter may be a great idea – I’d certainly back you.



    1. Re the external Xtal the uC does have an internal clock source however I’m not game to try it as the sample clock accuracy is important for the modem. Not that important however, +/- 2000ppm is OK. However I’d like to minimise risk on rev 1.0.

  9. Hi David,

    Gosh that’s a big comment!

    Well the current SmartMic PCB is 8,000mm sq, my FT817 mic is 60×90=5,400 – not hugely different. Plenty of larger rig mics than my FT817 too, e.g. those with keyboards. My Baofeng HT is 100×60 and that’s quite comfy. So I think we are in the ball park – close enough to test the “mic” form factor idea.

    I am sure your suggestions will give Rick some ideas. You are also welcome to try custom permutations of the design. It’s open hardware so go for it! The mods you suggest should run with the software we are developing.

    Yes I’d like to see internal battery operation, but we need to draw the line of features somewhere for rev 1.0, and 6-12V is pretty common – even on mountain tops! IIRC I think we need up to 200mA, depending on speaker volume. We haven’t done much analysis of power req yet.



  10. Certainly understand the need to be conservative and limit the scope for version 1! Ouch, 200mA is quite a lot – my whole transceiver only draws 100mA on receive (KN-Q7A)! I guess that’s DSP for you! You could probably use the internal clock source as most allow calibration, but then you’d make the setup more complex, so understand why you would want to stick with a crystal.

    If I had lots of spare time, I’d be tempted to try and adapt a very compact variant, but unfortunately I’m rather time poor and have three other projects on the go ๐Ÿ™

    I’ll continue to watch with interest.

  11. I think Rick estimated 160mA peak, largely due to full volume (0.7W) on the speaker, it’s not the quiescent figure which I imagine is << 100mA. I suspect the uC is actually very power efficient, we just haven't explored that yet.

  12. It seems an exciting project to work on. I heard about it from Bruce Perens and I am sure it is going to be a major step in spreading the use of FreeDV.

    One question though: does embedded mean that the codec can’t be upgraded? It would be a shame if the hardware becomes obsolete when Codec 2 gets further developed and becomes non backward compatible.

    I also would go with a kickstarter campaign. I would surely sign up for one.

    73 de Hans

    1. Hello Hans,

      You will be able to reflash the firmware at any time via a USB memory stick, or USB, or JTAG connection to a PC.



  13. This is a great addition to ham radio. Awesome project! I’m very much looking forward to being able to mess around with FreeDV out in the field.

  14. All,
    The 16 MHz internal RC oscillator is factory-trimmed to offer 1% accuracy over the full temperature range. I’m not sure what David’s clock accuracy requirements are, but 1% doesn’t meet specs for USB operation. Currently, USB is used to flash/re-flash program memory via boot loader built into processor and images provided by David.


    1. I think we need +/-2000ppm for the demodulator. Hmmm, I think that’s +/-2%? Might be worth trying, although given it’s not good enough for USB. I’m just curious.

  15. All,
    With regard to power consumption…
    Keep in mind that SmartMic is replacing a PC.

    With regard to size…
    Easily 1/3 of the PCB area is used for connectors. I am currently working at rotating the electronics 90 degrees, which gets the 100mm x 80mm size oriented in the right direction. Our plan from day one was to get something that works, then refine.

    Rick KA8BMA

  16. Is there enough horsepower left in the chip to handle digital data (either dedicated or along-side an audio stream)? I’m thinking of various other options:
    GPS location ‘burst’ when transmitting
    ID burst
    send/receive data when not talking (D-RATS style communication)

    1. The firmware isn’t finished so we don’t have an accurate CPU load estimate ATM. But yes, I imagine these features would fit CPU-wise. One benefit of “owning the stack” (i.e. hardware/modem/codec/control software all open source) is we can do as much optimisation as we like if more CPU is needed. Try doing that with a binary blob vocoder or modem.

      1. Indeed… another thought was if it can do full-duplex (satellite work or monitoring your own output). Imagine if this was tied into the radio bits as well… the digital portion could auto-tune the radio as it drifts down in frequency, making it super-easy to talk on a satellite (just lock onto a signal, and then see how fast it drifts off frequency to command the radio to keep up with it, both transmit and receive). This would be more useful on SSB than FM birds…

        Of course you could just use 2 smartmics.

        Would this unit benefit from being plugged into the ‘back’ of the radio, into the TNC port, and take advantage of the 9600baud setting available on most radios? Could we adjust smartmic to increase it’s baud rate, and throw more FEC/data across the radio?

        Also, I’ll also say that I’m glad this is open source. I’d see a few local ‘makerspaces’ that has a ham radio club to jump on this and run a few ‘learn-how-to-solder’ classes and assemble some of these as kits. If we could buy the smartmic un-assembled for a cheaper price, I’d imagine we’d have a few groups buy these in bulk for these classes. A stack of PCBs, and a bag of components.

        1. The fdmdv modem is pretty good at tracking frequency offsets, but not sure how I’d do that for SSB. FreeDV on the PC already runs full duplex BTW.

          Sure you could experiment with different connections to the rig, and bit rates – it’s all open! My particular interest is turning a $60 HT into a DV radio.

          For kit assembly you might want to re-layout the PCB to use larger components, it’s all surface mount ATM

          1. Agreed, this is something I’ve thought about/wanted for awhile… turning my existing radios into DV radios. I could see this as the ‘base’ to build a more more complete DV radio system off of (to replace DSTAR’s functionality).

  17. This looks to be a great way to get more people to use FreeDV ๐Ÿ™‚

    $195 (I hope!) to get a radio (or more) into DV without the need for a dedicated PC. I’m bookmarking the page so I can watch for progress and looking forward to the time I can see a kit offered.

    For those of us who run Windoze, and whose PCs are required to spend most of the time in the “home office”, this promises to be a god-send, and it could be used on the HF rig, as well as experimenting with the V/UHF FM set.

    All power to the gurus who are doing the coding as well as the hardware design and procurement research.

    Stu, G3OCR

  18. Fantastic, I want one too. I think this is going to be huge in the world of har radio. Just let me know if you are looking for folks to beta test for you !

  19. WOW this really a step in the right direction I want one too. (very keen as a beta tester Hi Hi) DV has a small following in South Africa but with this tool I am sure interest will grow.

  20. Gimmie, gimmie, gimmie!!!!

    Kickstarter is a great idea for this kind of project. Where do I sign up?

  21. Dear All, I’ve just discovered this project and I’m so excited.
    When/Where I can order the smart mic?
    Thank you again for your fantastic job!

  22. Hi David,

    I am watching this project with great interest.
    What do you need from us, your potential customers, to advance this product to being commercially viable? How can we help?


    1. Hi Ben,

      That’s a good question! On the technical side I have quite a few C programming tasks that don’t involve DSP knowledge. I could use some help with them.

      By the end of 2014 we will have Beta SM1000 hardware ready for purchase and use. Feedback on that (and even better small mods to the hardware to improve it) would be very welcome.



  23. I have as many questions as anyone else, but I looked at the Const-SM1000-C.pdf and in that document you can see the connector layout.

    To me, this IS a breakout box, not a hand mike…don’t get me wrong, I can see what the plan is…

    But look at the row of connectors at the bottom.
    Power IN
    RJ-45 (to radio I assume)
    Speaker OUT

    RIG Speaker
    RIG Mic

    So it seems you could lay this on the table, (or stick to radio) hook up your headset and foot switch…if so desired.

    BTW What is the USB connector at the Top (I assume it is the top) used for. Power is at the bottom…digital interface?

    1. The SM1000 is designed to operate in the “small box on the desk” form factor, or as a hand held mic. Currently USB is used for reflashing from a Host PC.

  24. Thanks for the response, I apologize, I did not realize this was the oldest entry (linked from a QRZ forum entry about FreeDV, I caught up to the most recent articles, and you explain all about the handmic or desk box options…

    I look forward to plugging this into my Yaesu!


  25. Hi David,
    The idea of Kickstarter funding has been mentioned a few times in this thread, with no conclsion as far as I can see. As development appears to be continuing without extra funding I guess it is not needed?
    I think once the beta units are out and being demonstrated, you’ll need a production capability to come on-line and ramp-up quickly to meet demands. Otherwise we’ll quickly have a two class system – those with smart-Mics and those waiting for them to be built!

    I’m looking forward to using the mic with my FT817 from a SOTA mountain top here in Germany as soon as possible in the new year.

    73 Ed DD5LP / VK2JI.

  26. Hi Ed,

    I’m OK for funding production of the first Qty 100 Beta order, although a kickstarter might be useful for other reasons, like marketing and publicity. But only so many hours in the day.

    Thanks for your enthusiasm about the SM1000, once we get a feel for sales on the first 100 units we can plan more production. There are other ways to find cash flow if required, like pre-orders. High demand is a “good” problem I can manage ๐Ÿ™‚

    Good luck with the SOTA work.



  27. This is interesting! Had heard about FreeDV previously, but just read about it in QST. Re-kindled my interest. I will want one to play with! I can imagine DV displacing SSB…

  28. Hi David,
    thanks for codec2. i just used it and its fantastic… well done ๐Ÿ™‚
    but i used it on linux x86 architecture. so i hav doubt is this compatible with ARM or Cortex architecture… becoz i am planning to use codec2 in one of my project based on cortex m3 microcontroller.
    so if possible will you plz tell me is this possible to port this? if es then how i can port this codec2 on my cortex m3 board.

    thanks & regards,

  29. Hi david,
    thanks for your kind and quick reply..

    1) the micro-controller which i am using is CC2538 from Texas instruments and its a Cortex -M3 based. and it dont hav any FPU.
    so isn’t it possible to port Codec2 on this micro-controller ?

    2) is there any other way to port codec2 on cortex-M3 micro-controller without FPU support ? becoz now i am in middle of my project and already i did lots of work on cc2538 so at this time its not possible for me to change the micro-controller.

    i hope u can understand my situation…
    waiting for your reply..
    Any help or suggestion will be appreciated..

    Thanks & Regards,

  30. What’s the latest ETA David? I’m moving QTH next month and hope to get an/some antenna(s) up for the higher HF bands. I could probably run a “shack computer” under Windoze for Codec 2, but it would be much neater to use Smartmic ๐Ÿ™‚

    The first production run ETA has been mentioned as “late 2014” for some time, and we’re not far from Christmas now. I know “things take time”, but it would be great to buy myself a Christmas present!

    Stu, G3OCR

  31. Hi Stu,

    Latest estimate is shipping early Jan. Edwin is currently getting two pre-beta units made. We thought this would be best as quite a few footprints have changed since the prototype. Once these are tested by Rick and I (mid Dec), we’ll press the button for Qty 100 manufacture and they’ll be shipped worldwide direct from China.



  32. Scuse me, but my question is very simple.
    Can I use an external module to operate
    in Digital Voice (Codec 2) in a normal
    2 KHz Bandwith (SSB Transceivers) ?

    If yes, what are the performances compared
    with the Standard SSB Signal to Noise ??

    Best regards and an happy 2015

    Paolo, IW2ACD

    1. Hello Paolo,

      Yes the SM1000 is an external device that will let you use your SSB radio for HF DV. Or you can use the FreeDV application on your PC with two sound cards. Current performance is not quite as good as SSB on fading channels. However new FreeDV modes are being developed that will improve performance in 2015.


    1. Hi Mark,

      Yes there have been some developments, sorry I should have posted about them. I’ve tested 1 pre-beta (see part 10) and it works fine. We are scheduled for production in March and I will start taking pre-orders as soon as I set up the store page! (next few days).



  33. Why would anyone want to buy hardware for this mode, when it can be done with software? I already have a rig (using USB interface), and a PC hooked up to it! With the right software, I already have what is needed!



    1. Hi John,

      Mobile and SOTA operation, PC free operation, elegance, ease of set up, ease of use, low power consumption …..


    1. Some people have used the FreeDV 1600 mode (a FDMDV modem) over FM radios and it seems to work. Later in 2015 there will be a firmware upgrade for a VHF FreeDV mode with a more suitable modem.

  34. Hello David..! I’m very excited about this new product, which I assume it’s going to become a “must have” gadget for clever hams..!
    I’ve been using FreeDV since the first version released, with excellent results, and that is why I carry my laptop with me every
    time I go into the fields.
    But in order to leave my computer behind, I’d need a gadget for PSK-31 and JT-65. Do you think it is possible, for future versions,
    to include these protocols in your SM1000? It would need a 2×16 LCD display and maybe PS/2 (easier) or USB keyboard port.
    If I’d have a FreeDV/PSK-31/JT-65 gadget, I’d sleep embraced to it every night..!! ha ha.
    Thank you so much for your work. Julian, LU2DJL

    1. Hi Julian,

      Adding PSK-31 and JT-65 is a fine idea. The STM32F4 would be “idling” on PSK31 (it already does PSK at 1600 bit/s) so CPU load is not an issue. There is also plenty of flash available for extra modes.

      I am sure a keyboard could be connected to the STM1000 USB OTG port, or even a tablet/smartphone to use as a GUI. A LCD (or even touch screen) would be straight fwd to add too. There is also a RS232 type UART broken out on internal pins, and some GPIOs.

      The issue is my time! I have many important projects lined up …. and there is just one of me. However I am very happy to work with anyone who wants to integrate new software into the SM1000.



  35. I’m interested in your thoughts on using this codec in an open source, non-vendor (radio) specific version of DMR.

  36. Ordered my SM1000 through “AliExpress” last week. Any idea as to the shipping time. I have been using FreeDV for a couple years. The SM1000 has me excited.
    Pace, Florida

  37. Thanks, David. I am looking forward to the SM1000. I am anticipating considerable growth as more hams acquire the 1000 and FreeDV garners a large place in the digital communications arena.


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