Selling point : Our simplex and duplex systems all use an offset of 0, which is our duplex system. Regardless of simplex or duplex, the offset is 0.
We are using high-precision temperature compensated crystals, so it is 0
We use high cost TCXO crystal with extremely low bit error rate, offset of 0,
and frequency error of 0

STM32_MMDVM_HS HAT  Guide
new pi4b need remove R1 Resistor.

STM32_MMDVM_HS HAT Rev1.7 Guide

1.Hardware add (SDA,SCL)R20,R21 Connect stm32 i2c 2 bus to OLED,and raspi.  oled message pwr on without RPI using mmdvm_hs custom fw,and i2c 2 bus.

2.Support i2c communition with raspi

Setting For Pi-star software and raspberry hardware (rpi 0-3) new pi4b need remove R1 Resistor.

Controller Mode:Simplex Node

Radio Frequency : Freq:144-148,219-225,(Main Band)420-475,842-950

Example:438.000000

Radio/Modem Type:STM32-DVM(GPIO)

14.7456 TCXO with RXOFFSET=0 TXOFFSET=0

Quick start:

1.download image https://www.pistar.uk/downloads/  write it to card

2.insert card to rpi  

3.wait to boot 5 minutes connect wifi Pi-star-setup pass raspberry

4.open http://pi-star/admin/
5.set freq ,dmr id ,dmr mode,add home's wifi ssid...
Default Username: pi-star
Default Password: raspberry

to support i2c communication change MMDVM_HS code(by Andy Uribe CA6JAU)->Config.h

// Host communication selection:

//#define STM32_USART1_HOST

//#define STM32_USB_HOST

#define STM32_I2C_HOST

to disable i2c 2 to raspi and oled just remove R20,R21  

update new FW: (pi-star / expert / ssh access / user :pi-star pass:raspberry)

sudo pistar-mmdvmhshatflash hs_hat

ps:update new FW no oled pwr on message.