it's completely irrelevant, which OS runs on the host computer, if I'd like to know how I can control the pins RX5/TX5. Don't you think so?
Ok, well, here's my best attempt to help you understand how to use Serial5, without any disclosure from you about what you're actually trying (that isn't working).
Here is a known good program which transmits data on TX5 (pin 33)
Code:
void setup() {
Serial5.begin(9600);
}
void loop() {
Serial5.println("Hello World");
delay(500);
}
I tested this just now on a Teensy 3.6 with a FTDI TTL level USB-serial cable. Here's a photo of the test running on my workbench.
To view the data from the FTDI cable, I ran the "seyon" terminal emulator on Linux (Ubuntu 14.04 64 bit). Here's a screenshot.
It's also possible to view the data in the Arduino Serial Monitor. To do this, I had to select the correct port from the Tools > Ports menu. Here's a screenshot:
Notice in this picture that /dev/ttyACM0 also appears. It is the USB serial which communicates with "Serial" on Teensy. But since this case is using the FTDI cable, the other /dev/ttyUSB0 port needs to be selected, because that is the port for the cable. You must select the correct port to make this work.
Here's a screenshot when I open the serial monitor.
I really do want to help you. But since you refuse to give any info about what you're actually doing, I can not guess what you are doing wrong. I hope these screenshots, the photo and this code helps you to repeat these steps.
As I and others tried to explain, all you need to do is use the usual Arduino Serial functions, but use "Serial5" instead of "Serial" or "Serial1". It really does work very easily.
This page has the complete documentation on all the functions. Hopefully this helps?
https://www.pjrc.com/teensy/td_uart.html
If it still doesn't work for you, perhaps try another computer. Or you could post a message with photos and exact details about what you are actually doing. If something is wrong and you show us what you're actually doing, odds are good we'll be able to see the problem and help you solve it. But this only works if you actually show what you're doing.