While routing the project slipped from simple arduino chip towards a full blown micropython platform and roughly 50 I/O pins. http://docs.micropython.org/en/latest/ This 5$ chip is super rich in interfaces, memory and insane speed The core of the board is compatible to the pyboard, so all software and tools managed by that community can be used for PA radio play. The interface and IO options are sort of Ham Radio specific, so I call the design a "Hampy" STM32F405RG microcontroller 168 MHz Cortex M4 CPU with hardware floating point 1024KiB flash ROM and 192KiB RAM On-board 3.3V POL voltage regulator, capable of supplying up to 3A, input voltage range 5V to 17V Micro USB connector for power and serial communication DFU bootloader in ROM for easy firmware upgrade and flash drive function Total 51 GPIO channel 14 Relais output coked with LPF + ULN driver chip 12 ADC with 1kHz LPF 2 ADC 2.2MS/s 2x DAC 2.2MS/s 2x I2C (1 is 12V level extender) 2x UART 1x SPI / I2S options for software are now: 1. STM32Cube - full STM IDE and C/C++ environment for the geeks 2. use it as a power arduino: https://www.stm32duino.com/viewforum.php?f=35 3. as a pyboard running full micropython: http://docs.micropython.org/en/latest/ bootloading requires minimal tools: FTDI USB-serial cable to burn the image once a lifetime after that, use arduino IDE via USB DFU or micropython via usb file system. it is a flash drive disk to a windows/linux/PI abundant choice of displays. I will try to add an e-paper (instead of stupid LED blinking) https://eckstein-shop.de/Waveshare-27-inch-264x176-E-Ink-E-Paper-Raw-Display-three-color-Arduino a buzzer to allow error codes to be acustically send as morse code? Several use-case for the connector: act as PA interface to be controlled by different Radios, simple arduino code available here: https://remoteqth.com/wiki/index.php?page=Band+decoder+for+Arduino ICOM CIF,Anlaog, YAESU, Kenwood CAT, or general Serial interface. Hermes-Lite 2 I2C interface (in both directions = we can send measured data back to SDR PC software or HL2) The board can drive 16x 30V @ 500mA has free wheeling diodes so directly able to drive 5,12,24V Relais without additional peripheral. Analog measurement with stable low pass filtering electronically and digital. The I/O is massive oversampling analog values. 2MHz sample rate allows even oscilloscope type of triggered scans up to 1MHz (no idea for what though) t lest there is a abundance of data that will allow to raise analog sampling precision mathematically to be improved to 16/18bit ADC resolution. The DB9 connector contacts are mapped by a jumper array to change different connections, like UART vs I2C vs serial by jumper settings we can choose which pin does what on the connector my measurements in the PA are: 3x RF power forward, 3x SWR power, inrush current, voltage, 3x temperature, BIAS current, output frequency each measurement will be written to a 10min ringbuffer and need to be transferred to PC by I2C? so I can have a chart recorder on it. The analog out may be used to output mp4 speech messages or simply morse text.