This link is only for Mini Duplex MMDVM boardsSetting up Pi-star software and raspberry hardware (rpi 0-3) New pi4b needs to remove Right SocketPi-star general configuration for MMDVM_DUPLEXSet controller mode: duplex repeater or simpleRadio frequency: Freq: 144-148, 219-225, (main frequency band) 420-475, 842-950Duplex mode: Example: RX:438.000000 TX:433.000000Duplex mode: Example: RX:145.000000 TX:433.000000Simple mode: Example: RX:438.000000 TX:438.000000Radio/Modem Type: STM32-DVM/MMDVM_HS-Raspberry pi Hat(GPIO) or any other (GPIO board)Options: (not needed now, some older boards need to be set)Admin->Expert->Edit MMDVMHOST->RXOFFSET=0 TXOFFSET=0 (default value in pistar)(Update: 2019/2 new 3225 TCXO so 0ffset is 0 )Update new firmware: (pi-star/Expert/ssh access/user:pi-star pass:raspberry)sudo pistar-mmdvmhshatflash hs_dual_hatThe default bit error rate is less than 5%, and the default 0ffset is 0. If the bit error rate is greater than 5%, as long as the signal can be received, it can be corrected through 0ffset.

Features:
1. Versatile: This duplex MMDVM hotspot supports DMR, P-25, D-Star, and System Fusion, accommodating various radio communications preferences.
2. Raspberry Pi Compatible: The hotspot mounts cleanly on all current types of Raspberry Pi, inclusive of the Pi Zero W, 2W, 3B+, 4B, and 4B+, making it ideal for Raspberry Pi enthusiasts.
3. Dual Mode: The device supports both Duplex and Simplex modes, allowing for flexible communication sessions. In Duplex mode, it supports 2 time slots with simultaneous Tx and Rx.
4. No Ofset Required: With the best adjustment set at TX=0, RX=0, this device requires no ofset, simplifying the setup process for users.
5. Indicator LEDs: The board includes built-in LEDs that indicate status, along with status words on the shell for clear and straightforward device operation.

Package Includes:
1 x Duplex MMDVM Hotspot Board