|"Sometimes I needed an external serial monitor like the Serial Monitor in the Arduino Editor, to see what is going on. So I made one.|
The first picture shows an example how could be it designed.
For the ESM I used an Atmel Atmega328 (based on the Arduino-Board) because it have an internal SRAM with 2KBytes. It's necessary for the big data processing.
So you need more than 1KByte SRAM."