Hi! I wonder if Serial.print/println could be arranged in a way that interrupts from the UNO-UART would make the UNO load the next character to be transmitted. This would make the UNO able to do its work without the "long" delay caused by waiting for the entire message to be transmitted. Of course…

Serial output using interrupts

holmes4 May 25, 2018, 7:10am 12

Sounds like the op needs to produce LESS output to keep the speed up!

Mark