LeananKite

This my original code with the definition of the serialbuf: #define HWSERIAL1 Serial1 unsigned long now; #define USB_TIMEOUT 1000 byte...

I think the problem is the Serial.begin in the setup() function. This creates unexpected side effects.

:) you are right. And some secrets must remain unrevealed.

Oh, my, it works!!! I do not understand why. Can you explain it to me, please?

I have a model car and I receive information from remote control by Serial1 (RX1) on Teensy 4.1. When I first connect my Teensy with USB on Serial and turn on the battery everything works fine. I see my wheels moving accordingly. When I just turn...