SmartMic Prototype PCB Ready for Manufacture

Over the past few weeks Rick Barnich KA8BMA has been doing some fine work on the schematic and PCB design for SmartMic. Yesterday Rick and I had a PCB and schematic review meeting over Skype, and Rick is now working on a few small changes. The PCB board layout will go in for manufacture this week by my good friend Edwin Chen from Dragino. I plan to be soldering the first prototype in early July.

Here is the current schematic, it would be helpful to have some more eyes on it to see if we have missed anything!

The design is now just 90 x 65 mm, so I feel we have achieved our PTT hand-held microphone form factor requirement. As the connectors are at either end of the PCB, it can also be mounted in a small box. Rick and his son are working on a 3D printed enclosure for the prototypes, we are undecided on the final enclosure.

Here is an image of the PCB, note the mechanical details showing the connector locations. Click for a larger version.

From my side I’m working on squeezing the FDMDV modem into the STM32F4 micro-controller. The main issue is run time memory, the high over sampling rate (M=160) means we are using too much RAM. No matter, I’ll re-arrange a few loops and trim that down a bit.

7 thoughts on “SmartMic Prototype PCB Ready for Manufacture”

  1. That looks great :)

    Maybe a bit large (to my liking) for a Fist Mic, but just fine for an add-on “FreeDV Box”.

    Is the controller chip flash-able? – At the current time, I have the impression that FreeDV is still not in whatever will be its final version, so I envisage the need for upgrades will come along – and this would hopefully be possible from a (Windows?) PC. Is that the purpose (or one of them) of the USB connector?

    You seem to have packed a hell of a lot (especially all the I/Os on peoples’ “wish-lists”) onto that board.

    A magic job! Kickstarter? Or are you set up for a production phase? Still $195?


    1. Hello Stu,

      Yes the uC can be flashed via USB fro a Host PC or a USB memory stick. Yes there are many people asking us for a Kickstarter!



  2. I wouldn’t worry too much about the box size, this unit will sit next to the rig.

    Some feature requests:
    * runs either on 12V (13.8V) so it can be powered with normal rig power.
    * The off switch also bypasses everything

    A kickstarter would be great if you need help ramping production. I’m ready to order any time!



    1. Hi Peter,

      Yes it runs from 6-16V.

      Hmm, complete bypass on power off is a good idea for future revisions. I suspect we might need relays for that. It’s been suggested that a Kickstarter would help marketing and promotion, as well as helping ramp up production.



  3. Hi David.

    Usb is nice but VERY proprietary A rather nice open debug expansion port can be made by combining CPU power with serial. It only takes 3 or 4 pins. I have a LOT of stuff that just plugs in and runs. I usually add a few other nearby pins making 10 pins total on a 0.1 pin array. Most cheap micros can then run off system power and talk to the host via serial (half or full duplex). This makes an easy way to add features and try out new stuff…. Add gps or voice logging…. Add digital modes…. Sometimes I add spi to the firmware for faster data flow. Just a few pins. Not much PCB space. Big payoff later :).

    This makes the ‘mic’ a building block that can be interconnected with other devices either as a host or slave.

    Just my two cents :) :).


    1. Hello John,

      Check out the schematic – we have a 3 pin header connected to one of the uC’s UARTs, and also have some test pads fanned out from the uC from the I2C port. No room for any more headers, and we need to draw the line of effort for this rev. However it’s open hardware, so feel free to grab the files and go for it :-)



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