I'm not good at this, so forgive me.
Not too long ago, I had trouble with a CSS selector, and the problem was fortunately solved, however.
I now stand with the problem that I'm trying to transfer (a string) information from my Node-red, a clock time of 14:00 (for example) and I'm not having much luck.
Here's a picture of the flow.
I know that the Arduino and Serial can't share the port, but it's to show that I have tried two things. First with the Arduino (which I can mostly get connection with) and then with a serial. I had a light shine up if it received something, but alas to no luck.
Any suggestion what functions I should use in Arduino? The Arduino node writes to pin 13, am I to expect that pin 13 just saves whatever I send to it?
If you want to send serial data to an Arduino and are having issues, the easiest thing to start with is to validate your Arduino code. Connect it to the machine you use to program it and use the serial console in the Arduino IDE to test sending the data you want.
Use serial write statements generously in your Arduino code to get debug output - use a function and a switch variable if you like so that you can easily turn on/off the debug data.
Once you've validated that, the next thing to do is to ensure that your serial port is correctly configured on the Node-RED device. It is easiest to do that with a terminal program that supports serial ports. That checks that the device and receive and send data correctly.
If you have debug output coming from your Arduino you can now use a serial-in node to check that Node-RED actually connects properly to the serial port.
Finally, you can try sending data which hopefully you mirror back to the serial port so that you can see the response inside Node-RED. If the light is still not working, you know you have a logic error on the Arduino side or you are not sending what you think you are from Node-RED - use a debug node to check that and make sure you don't have anything odd in there - linefeeds can throw out your Arduino code if you haven't properly trimmed and validated the input - which you should always do with any external input to prevent security and operational problems.