To realize a multimode digital repeater, G4KLX has developed a very complete software called MMDVM (Multimode Digital Voice Modem). It is compatible with the main digital modes (to date, C4FM, DSTAR, DMR Tier 2 and now P25).
I realized this PCB trace, like some other OM, with components of classic sizes (integrated circuits in DIL format, resistances in quarter of Watt, …). There is only the TCXO which remains rather small. To get rid of a SMD formatting component, I chose to install a TCXO HCMOS directly compatible with 3.3V. The reference chosen is FOX924B-12 with a stated stability of +/- 2.5 ppm.
The plate is inserted directly below the Nucleo STM32 board, on CN7 and CN10 connectors.
The following features have been added to the previous MMDVM interface card running with an Arduino Due:
- Measurement of RSSI signals sent by the receiver (with validation jumper)
- An LED signaling the life of the deck (Live Led)
- Four LEDs indicating the active mode (DStar, DMR, YSF, P25)
- Integrated radio interface pins between the two mini-Din connectors
- Switching to a single mini-Din connector Transmitter / Receiver
- Nextion touch screen LCD interface
- Four additional mounting brackets 3mm (50.00mm x 75.56mm)
Diagram of the MMDVM board for Nucleo STM32F4 – The MMDVM filter is under CC BY / SA / NC license established by KI6ZUM
PDF Format : Diagram MMDVM shield for STM32
MMDVM shield for Nucleo STM32 (Top view – dimensions in mm)
MMDVM shield for STM32 – Rear face with ground plane, with 2 femal connectors
Here the Bill Of Materials:
| Name | Value | Precision | Mounting box |
| C1 | 10µF | D4R2,54_ELKO | |
| C2 | 10µF | D4R2,54_ELKO | |
| C3 | 10nF | 10% | 3X5R2,54 |
| C4 | 47µF | D4R2,54_ELKO | |
| C5 | 47µF | D4R2,54_ELKO | |
| C6 | 10nF | 10% | 3X5R2,54 |
| C7 | 10nF | 10% | 3X5R2,54 |
| C8 | 10µF | D4R2,54_ELKO | |
| C9 | 47µF | D4R2,54_ELKO | |
| C10 | 1nF | 5% | 3X5R2,54 |
| C11 | 1µF | D4R2,54_ELKO | |
| C12 | 470pF | 3X5R2,54 | |
| C13 | 39nF | 5% | 3X8R5,08 |
| C14 | 10nF | 10% | 3X5R2,54 |
| C15 | 100nF | 3X5R2,54 | |
| C16 | 47µF | D4R2,54_ELKO | |
| C17 | 39nF | 5% | 3X8R5,08 |
| C18 | 1nF | 5% | 3X5R2,54 |
| C19 | 100nF | 3X5R2,54 | |
| C20 | 47µF | D4R2,54_ELKO | |
| C21 | 100nF | 3X5R2,54 | |
| C22 | 22nF | 3X5R2,54 | |
| C29 | 100nF | 3X5R2,54 | |
| C-RX1 | Receiver | DIN6POL-MINI | |
| C-TX1 | Transmitter | DIN6POL-MINI | |
| D1 | LED SQUELCH | LED_3mm_vert | |
| D2 | LED PTT | LED_3mm_rouge | |
| D3 | LED POWER | LED_3mm_jaune | |
| D4 | LED DSTAR | LED_3mm_vert | |
| D5 | LED DMR | LED_3mm_vert | |
| D6 | LED YSF | LED_3mm_vert | |
| D7 | LED P25 | LED_3mm_vert | |
| D8 | LED LIVE | LED_3mm_jaune | |
| IC2 | MCP6002-I/P | DIL8 | |
| IC3 | MCP6002-I/P | DIL8 | |
| IC4 | LP2950ACZ3,3 | TO92 | |
| Q1 | 2N7000 | TO92 | |
| Q3 | 2N7000 | TO92 | |
| R1 | 330 | 0204_MET | |
| R3 | 4,7K | 1% | 0204_MET |
| R4 | 5,1K | 1% | 0204_MET |
| R5 | 22K | 1% | 0204_MET |
| R7 | 4,7K | 1% | 0204_MET |
| R8 | 4,7K | 1% | 0204_MET |
| R13 | 10K | 0204_MET | |
| R14 | 330 | 0204_MET | |
| R15 | 47K | 0204_MET | |
| R16 | 1M | 0204_MET | |
| R17 | 47K | 0204_MET | |
| R18 | 5,1K | 1% | 0204_MET |
| R20 | 220 x 8 | SIL9 | |
| R21 | 22K | 1% | 0204_MET |
| R22 | 4,7K | 1% | 0204_MET |
| R23 | 22K | 1% | 0204_MET |
| R24 | 27K | 0204_MET | |
| R25 | 47K | 0204_MET | |
| R30 | 100K | 0204_MET | |
| R98 | 100K | VISHAY_64W | |
| R99 | 100K | VISHAY_64W | |
| TCXO1 | 12MHz (FOX924B-12) | CFPX-104 | |
| J1 | Radio interfaces | Stiftleiste_1x07_G_2,54 | |
| J2 | Nextion LCD | Stiftleiste_1x04_G_2,54 | |
| JP1 | Connector Sel. | Stiftleiste_2x02_G_2,54 | |
| JP2 | En.RSSI | Stiftleiste_1x02_G_2,54 | |
| CN7, CN20 | Female conn. 2×19 | Stiftleiste_2x19_F_2,54 | |
In order to make your copy of the electronic card, you will find here all the production and drilling files of the standard Gerber card : MMDVM STM32 F5UII v2 – licenced CC by-nc-sa
Here is the board mounted, tested and functional
MMDVM shield mounted under the STM32 board of ST Microelectronics
The STM32F4446RE behind the MMDVM filtering shield
In the table below, you will find the pinout to follow according to the board. Like my previous MMDVM board for Arduino uses the NTH definition.
Sur le tableau ci-dessous, vous retrouvez le brochage à suivre en fonction de la platine. Comme ma précédente platine MMDVM pour Arduino utilise la définition NTH.
And for tuning, I invite you to read the article dedicated to the installation of MMDVHost and the DMR mode calibration.
If you are interested to participate in a possible future new grouped order, leave your email below to be reported !
