MMDVM board for Arduino Due

To build a multimode digital repeater, G4KLX have developped a complete software called MMDVM (Multimode Digital Voice Modem). It is compatible of main digital modes (to date, C4FM, DSTAR and DMR).

This board interfac on one side transmitter and receiver and, on the second hand the Arduino Due. A computer (such as a Raspberry Pi for example) is connect via USB to the Arduino. This provide a complete controler for numerical repeater.


I design this PCB, like some other OM, with components in conventional sizes (DIL integrated circuit, resistors quarter-Watt, …). There is still a quite small component that is the TCXO . To eliminate an CMS component, I chose to install a HCMOS TCXO directly compatible of 3.3V expected voltage of the Arduino. The selected reference is the FOX924B-12 with an announced stability of +/- 2.5 ppm.

I replaced the bulky components (in TO220 housings) with equivalent components in TO92 case. The tests are to be carried out. However, even the largest components can be positioned, as I left the possibility of mounting one or the other versions. The board plugs directly on Arduino Due.

The MMDVM hardware is under KI6ZUM CC BY/SA/NC licence

The MMDVM hardware is under KI6ZUM CC licence BY/SA/NC

In PDF format : MMDVM F5UII v1.1

Here is the BOM

Pos Component Value Précision Case
1 C1 10µF D4R2,54_ELKO
2 C2 10µF D4R2,54_ELKO
3 C3 10nF 10% 3X5R2,54
4 C4 47µF D4R2,54_ELKO
5 C5 47µF D4R2,54_ELKO
6 C6 10nF 10% 3X5R2,54
7 C7 10nF 10% 3X5R2,54
8 C8 10µF D4R2,54_ELKO
9 C9 47µF D4R2,54_ELKO
10 C10 1nF 5% 3X5R2,54
11 C11 1nF 3X5R2,54
12 C12 470pF 3X5R2,54
13 C13 39nF 5% 3X5R2,54
14 C14 10nF 10% 3X5R2,54
15 C15 100nF 3X5R2,54
16 C16 47µF D4R2,54_ELKO
17 C17 39nF 5% 3X5R2,54
18 C18 1nF 5% 3X5R2,54
19 C19 100nF 3X5R2,54
20 C20 47µF D4R2,54_ELKO
21 C22 22nF 3X5R2,54
22 C29 100nF 3X5R2,54
23 C-RX1 Receiver Mini Din DIN6POL-MINI
24 C-TX1 Transmitter Min Din DIN6POL-MINI
25 D1 SQUELCH LED_3mm_vert
26 D2 PTT LED_3mm_vert
27 D3 POWER LED_3mm_jaune
28 IC1 LF33CV TO220
29 IC2 MCP6002-I/P DIL8
30 IC3 MCP6002-I/P DIL8
31 IC4 LP2950ACZ3,3 TO92
32 J1 RX TX Stiftleiste_1x06_G_2,54
33 JP3 GND Stiftleiste_1x02_G_2,54
34 JP4 5V Stiftleiste_1x02_G_2,54
35 JP5 TEST Stiftleiste_1x02_G_2,54
36 JP6 TEST Stiftleiste_1x02_G_2,54
37 Q1 2N7000 TO92
38 Q2 IRL530NPBF TO220
39 Q3 2N7000 TO92
40 R1 330 0204_MET
41 R3 4,7K 1% 0204_MET
42 R4 5,1K 1% 0204_MET
43 R5 22K 1% 0204_MET
44 R7 4,7K 1% 0204_MET
45 R8 4,7K 1% 0204_MET
46 R10 220 0204_MET
47 R11 220 0204_MET
48 R12 220 0204_MET
49 R13 10K 0204_MET
50 R14 330 0204_MET
51 R15 47K 0204_MET
52 R16 1M 0204_MET
53 R17 47K 0204_MET
54 R18 5,1K 1% 0204_MET
55 R21 22K 1% 0204_MET
56 R22 4,7K 1% 0204_MET
57 R23 22K 1% 0204_MET
58 R30 100K 0204_MET
59 R98 10K VISHAY_64W
60 R99 100K VISHAY_64W
61 TCXO1 12MHz (FOX924B-12) 2,5ppm CFPX-104
62 X49 POWER Stiftleiste_1x08_G_2,54
63 X50 A0 A7 Stiftleiste_1x08_G_2,54
64 X51 A8..DAC1 Stiftleiste_1x08_G_2,54

In order to make your copy of the electronic card, you will find here all production files and drilling of the card in standard format Gerber: MMDVM F5UII licensee CC by-nc-sa

Concerning transceivers, I will test the operation with two TM451E Kenwood (transmitter, receiver). This model has an “wide spectral” audio output. Indeed, for the digital radio protocols, you must use the audio output once used in packet radio (AX25) in 9600 baud.

The tests will follow on my blog, in the MMDVM category … Your comments are welcome below.

Here is the board mounted, tested and functional.

MMDVM mounted with discrete components

MMDVM mounted with discrete components – Rear view


MMDVM board mounted with discrete components

MMDVM board mounted with discrete components – View mini-Din connectors to radio transceivers


MMDVM board on its arduino due and mini 6 pin Din connections to the receiver and transmitter

MMDVM board on its arduino due and mini 6 pin Din connections to the receiver and transmitter. (TCXO at the top left)

If you would be interested to participate in a possible future new grouped order (MMDVM board), leave your email below to be reported!

If you would be interested to participate in a possible future new grouped order (MMDVM board, SvxLink Card), leave your email below to be reported!

10 thoughts on “MMDVM board for Arduino Due

  1. Great project, where can you get the board or a kit? Will it work with a DR1 and the tested?

    1. Thank you Frank,

      I have to finish the tests for validate the board. I will then offer the possibility the get one pieces of my liitle PCB stock, via my online ShopChip

      I think that DR1 is yes compatible for the MMDVM project. I know several D-STAR (with DVRPRTv1) working with this Yaesu analog/C4FM repeater. For example

      Also, here a video demonstrating a DR-1X converted in DMR repeater thanks to MMDVM :

  2. Bonjour,
    Beau travail.
    Je suis intéressé par un PCB (et peut être aussi d’autres OM du coin).
    Avez vous prévu une commande groupée ?
    Jeff, F5BCB

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  4. Bonjour,

    Je viens de finaliser les tests et réglages de ma platine ce week-end. Elle fonctionne de façon parfaite. Le TM451E que j’ai essayé en premier temps en émission ne permettait pas d’avoir le bon point de fonctionnement. A approfondir… Il est remplacé par un FT7800 qui fonctionne très correctement.

    Prochainement je vais ouvrir une commande groupée de carte MMDVM pour Arduino, avec kits de composants et câbles mini DIN 6 broches. Cela sera proposé sur
    ou suivez mes annonces via mon compte twitter



    I just have finalized the tests and settings of my MMDVM shield and Arduino this weekend. It works perfectly. The TM451E I tried first time oes not allow to have the right operating point. To be tested angain. It is replaced by a FT7800 which works correctly.

    Soon I will open a grouped purshase of MMDVM filter board for Arduino with component kits and mini DIN 6-pin cables. It will be proposed on
    Foloww my news via my twitter account


  5. Good afternoon, by the way, what are the dimensions of the pcb mmdvm for building the board, thank you

    Bonjour, au fait, quelles sont les dimensions de la platine mmdvm pour la construction du circuit imprimé, merci.

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  7. Hi, what did you use to solder the 12MHz TCXO onto the board?
    John G3VRF

    Salut, qu’avez-vous utilisé pour souder le TCXO 12MHz sur la carte ?
    John G3VRF

    1. To solder the TCXO, I use a conventional soldering iron equipped with a fine pointed tip. It is a question of heating the pad and the side of the TCXO at the same time. It is advisable to add a small amount of tin to the pads before soldering.
      Good luck with that.

      Pour souder le TCXO, j’utilise un fer à souder classique équipé d’une fine panne pointu. Il s’agit de chauffer la pastille et le coté du TCXO en même temps. Il est convenable d’ajouter un tout petit peu d’étain sur les pastilles avant de souder.
      Bon courage


      1. J’ai 2 TM451E avec lesquels je voudrais faire un relais MMDVM
        Pourrais tu me dire à quelles PIN de la mini-DIN du RX et mini-DIN du TRX tu reprends les signaux?
        J’ai un problème avec l’émission. Mon TM451 en TX ne passe pas à l’émission.
        Sur le RX, je prends GND et RX Audio et aussi le RSSI après une petite modif interne
        Sur le TX, je prends GND, PTT et TX Audio
        Merci 73
        Paul, ON6DP

        I have 2 TM451E with which I would like to make an MMDVM repeater.
        Could you tell me which PIN of the RX mini-DIN and TRX mini-DIN you take the signals from?
        I have a problem with the show. My TM451 in TX does not go on transmission.
        On the RX, I take GND and RX Audio and also the RSSI after a small internal modification
        On the TX, I take GND, PTT and TX Audio
        Thank you 73
        Paul, ON6DP

        1. Paul,

          Je ne crois pas que les TM Kenwood puisse faire correctement l’affaire pour du MMDVM; Mes premiers tests sur des 451 n’étaient pas probant et je me suis rapidement tourné vers les mobiles Motorola.
          Les matériels déjà testés avec MMDVM sont listés sur cette page

          Le câblage du connecteur Mini-DIN est droit et conforme à celui qui est sur mes platines MMDVM (voir schéma ci-dessus, en bas à gauche). Pour le RSSI, cet article suivant précise la modification que vous avez surement déjà mis en oeuvre.



          I don’t think Kenwood TMs can do the job properly for MMDVM; my first tests on 451s were inconclusive and I quickly turned to use Motorola mobiles.
          The materials already tested with MMDVM are listed on this page

          The wiring of the Mini-DIN connector is straight and conforms to the one on my MMDVM boards (see scheme above, bottom left). For the RSSI, this article specifies the modification that you have probably already implemented.


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