I did not post too much updates recently, but I was quite busy with new version of gateway. I manage to draw and let fabricate new PCB with 32bit ARM chip as main controller. For the purpose of first design I have shrunk the PCB to 100x100mm, but I have managed to squeeze all component I wanted there. Good news is that I was able to stay on 2 layers, and avoid much more expensive 4 layer PCB. I made the board at pcbway with the cheapest 6/6 method and the quality stays similar to my free boards. I will stay with them for sure.

After realizing that 100x100mm PCB includes all I need, I will most probably stay with this new format. To sum up there is:

• STM32F407 with 1GB of flash and 128KB of usable free RAM, running at 180MHz.
• LAN8720A Ethernet PHY with 10/100Mbit.
• Two step power supply with 12V to 4V switching and 4V to 3V3 LDO.
• Battery for RTC CR2032. STM32F407 has on-board RTC.
• 10 analog (balanced) inputs for PIR, smoke, ...
• 2G SIM800C module
• Radio for RFM69 or RFM95.
• 64KB SPI FRAM, bit expensive, but no wait times and blazing speed compared to I2C EEPROM.
• RS485 for wired connections.
• 2 relays for sirens.
• 1 tamper zone for enclosure. 
• Micro USB port for firmware update and direct console access.
• ST-LINK V2 port.
• 3 LEDs.

I guess it will pretty decent update to existing ATMega1284P.

More on https://openhomesecurity.blogspot.com/2019/09/gateway-2.html