I want to use an ATMEGA32u4-Beetle sensor to transmit data to a FrSky receiver via the S.Port interface. I use the Softwareserial library to invert the data. The High-TTL level of the receiver (see picture) is 4V, but the High-TTL level of the ATMEGA32u4 is only 2V. I have also tried various resistors between 5V and/or directly in the S wire but without success. What am I doing wrong?
ATMEGA runs with 5V