V3 F446 publish begin 2019-6-25, with STM32F446, FOX 12MHz TCXO, DB9 interface, 4PIN header for Nextion , higher performance .

With DB9 cable (option 0.5/0.75/1.0/1.5 Meter)

V3F4 Definition

1, Radio Data

Transmitter radio
TXA
PTT
GND

Receiver radio
RXA
RSSI
GND

Extend
HB heartbeat

Cancel
COS

2, Nextion
5V <-> HAT 5V
RXD <-> HAT TX
TXD <-> HAT RX
GND <-> HAT G

3, OLED
V3F4 Cancel OLED interface, please follow Raspberry GPIO definition, and jump line yourself.
http://mmdvm.bi7jta.org/search/label/Definition_GPIO_PCB_Case

4, Potentiometer ( High-precision )
RX : Adjust RX level
RV2: Secondary adjustment, suggest keep default
TX : Adjust TX level
RSSI: extend

5, External LED
J7 : Connect external led
J8 : Open,GND for external LED

Features:

Repeater and Simplex mode change anytime , through change the RX/TX board line order.
Support MMDVM mode DMR/YSF/P25/NXDN/DSTAR/POCSAG
Double timeslot in DMR mode, act as a mini Digital voice repeater.
Support VHF/UFH, frequency range: depends on your external radio.
High-quality ECS TCXO, stable with low BER.
Support Raspberry Pi 3B, 3B+, Pi ZERO, Compatible with NanoPi NEO, Orange Pi, Compatible to BlueDV(Required to add USBtoTTL or Bluetooth model)
With USB interface ,can connect to Raspberry Pi and PC, inner PL2303 model.
Upgrade through ST-Link, USB, GPIO, continue upgrade support.

Including && components
1x PCB with complete soldering,
1x External radio connector cable
1x Motorola Linker,(suit to GM300/M120/GM338/GM3188/CDM1250/GM340/GM950/FT-7800/FT-8900 etc)

Specs and Docs:
Power require: 5V2A
MCU: STM32F446x
TCXO: 12.0MHz ,FOX924
HAT: 1.6mm thick,unleaded process
Interface: MicroUSB, GPIO, DB9 female, 6 PinOut

After sales and support:
bi7jta@gmail.com