ESP-01, the simplest USD 1.50.- ESP8266 gets a firmware that allows the user to control it by serial port. Therefore it can be used along with any terminal, computer or microcontroller, which is equipped with a serial port (or USB port)
-) Connect / disconnect to WiFi and Flespi MQTT broker
-) Publish messages
-) Subscribe to topics / Unsubscribe from topics
-) Read the messages received
Furthermore a GUI is on developing process to demonstrate the use.
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