Building a system

You can follow these steps to build a working system.

Router

Set the 2.4GHz band of your router to "fixed" channel 1
- I personally use a separate Router defining a sepatate WiFi network (SSID) which works fixed on channel 1.

Program 1 (or more) ESP8266 or ESP32 with the sketch in espnow_sensor. Use ARDUINO IDE.
- Remember to set the appropriate #define USE_ESP8266 or USE_ESP32.
- If using several sensors, please remember to set unique UNIT (ID) for each of them.
HW configs:
- Connect RST to D0 (GPIO16) on the ESP8266 board.
  - Only needed for ESP8266. To be able to wake up from Deep Sleep.
  - On a WEMOS/LOLIN D1 Mini Pro V2.0.0 board you can do this by soldering the pad "SLEEP" (which connects RST to D0).
- Connect BAT to A0 on the ESP8266 board.
  - Only needed for ESP8266.
  - If you are using a battery and want to read the battery level.
- Connect a battery to the ESP board
  - You can of course run the sensor on USB 5V if you want. But the main idea with ESP-Now is low power which is needed for battery operations.
- Connect a Temp sensor to the ESP board.
  - Either use a SHT30 or DS18B20 sensor with provided code, or add your own code for any other sensor type.
As a first test you may skip these HW changes and just run without a temp sensor but send dummy temp data and with "manual" resets emulating a wake from deep sleep. You can also comment out the deep sleep code and just add a "delay(1000 * 10); ESP.restart();" for a 10 secs delay between restarts and readings. This is of course only for test as it will still consume lots of energy.

Program 1 ESP8266 or ESP32 with the sketch in espnow_gateway. Use ARDUINO IDE.
- Remember to set the appropriate #define USE_ESP8266 or USE_ESP32.
The ESP should normally run on USB 5V.
No HW modifications needed.