more readme

README.md

@@ -1,5 +1,7 @@
 # Giess-o-mat
 
+Firmware for automatic plant-watering machine, with web interface, LCD and keypad support, using two MCUs communicating via I2C.
+
 For more please also [take a look at Giess-o-mat on my website](https://www.xythobuz.de/giessomat.html).
 
 ## Quick Start
@@ -11,12 +13,49 @@ Before building for an ESP32 or ESP8266 target, execute the following commands,
     echo '#define WIFI_SSID "..."' > include/wifi.h
     echo '#define WIFI_PW "..."' >> include/wifi.h
 
-Then simply run the build for all supported configurations with platformio:
+Then simply run the build for all supported configurations with platformio.
 
     pio run
 
 You can of course also use pio to flash your targets.
 
+## Hardware
+
+In general, the project consists of two parts, the controller and the ui.
+They both communicate via I2C.
+In my own setup, I'm running the controller on an ESP32, and the UI on an Arduino Nano.
+It is also possible to run the controller with an ESP8266 or an Arduino instead.
+You can also run both on one board, but this was up to now only used on Arduino for testing purposes.
+
+Of course you need to take care of voltage levels when connecting different boards.
+I'm running the UI with 5V and the ESP32 is using 3.3V.
+For safety reasons I added a bi-directional I2C level converter between them.
+
+## Details
+
+The following targets are defined for this project.
+
+| Name          | Board            | Function   | Tested | Usable |
+| ------------- | ---------------- | ---------- | ------ | ------ |
+| esp8266_main  | ESP8266          | Controller | No     | ?      |
+| esp32_main    | ESP32            | Controller | Yes    | Yes    |
+| arduino_ui    | Arduino Pro      | UI         | Yes    | Yes    |
+| arduino_test  | Arduino Pro      | Both       | Yes    | No     |
+| leonardo_main | Arduino Leonardo | Controller | Yes    | Yes    |
+| leonardo_test | Arduino Leonardo | Both       | Yes    | No     |
+
+The "unusable" test targets were only used for easier development.
+They do not have enough GPIOs for all functionality!
+
+ESP8266 should work in theory, as long as the board has enough GPIOs, but I have not tested it.
+
+See 'include/config_pins.h' for the GPIO number definitions for the different configurations.
+Some other options can be set in 'include/config.h'.
+
+When an ESP is used, a webinterface and OTA updater will be included as well.
+For the ESP32, you can upload a new firmware using a webbrowser.
+Simply use the link on the main page of the web ui, then upload the '.pio/build/esp32_main/firmware.bin' file from the project directory after building.
+
 ## License
 
     Copyright (c) 2021 Thomas Buck <thomas@xythobuz.de>