Activity Forums Questions & Troubleshooting Issues with MEGA Serial1 Reply To: Issues with MEGA Serial1

  • JamesC

    June 1, 2023 at 10:46 am

    Just to close the loop on this.

    The issue here was that the MAX232 board that I mentioned above has an onboard 1k pull down resistor on the TX line. The Controllino MAXI and MEGA must have an internal pullup resistor installed on PD3 and that internal pullup resistor and the 1k pull down resistor were acting as a voltage divider.

    When I removed the 1k pulldown resistor the board worked fine with Serial1.