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Enable serial interface and configure baud rates.  Each serial interface is usually a TTL serial port on the microcontroller which may be connected directly to another device.  That other device may provide a USB port, or WiFi (SWS), or Bluetooth, etc.

Change this setting by editing Config.h then compile and upload using the Arduino IDE.


  • Default Value: 9600
  • Other Values: 9600,19200,57600,115200
  • Notes: The secondary interface SERIAL_B is a TTL serial port that is often attached to the WiFi or Ethernet Add-ons (which "bridge" the serial traffic to IP.)
  • Associated Options:
      • Allows upload of firmware to the ESP8266 WiFi Add-on through OnStep.  This is so you can update everything without opening the controller case to pull the WeMos D1 Mini (or ESP-01) for flashing.
      • Only two OnStep controllers allow this, the MiniPCB1 and MaxESP3, and then only if setup for it (shunts in the correct positions.)  Just connect to OnStep on its primary serial interface (SERIAL_A) and send the :hF#:ESPFLASH# commands to place the controller in firmware upload mode.
      • The Smart Web Server page has more information on how to flash the ESP8266.
  • Reminder:
    • This is usually not changed.
    • This port might not work on an MKS Gen-L due to the boards h/w design.