Serial Port COM3 does not receive or send any thing

Hi! Please can someone help me.
Only debug 10 displays the data, but debug 11 doesn't display any thing.
My flow is as follows:


Thank you very much for youy help

Do you have something physically attached to COM3?

Have you tried using putty or another hyperterminal to see if it responds to sending it 30?

Are you using a known working serial cable?

Have you tried the Serial Request node?

Do you have the settings correct on the COM config?

No, I have nothing physically attached to COM3.
The settings are correct on the COM3 config.
I do not tried anything else.
I just want to make a simulation: write 30 on the port com3 and read its content.
I am a beginner.
Thank you very much for your help.

Then this is your issue. you either need a device or a loop back or a pair of virtual com ports that are "wired".

What you are doing is transmitting data to a COM port TX pin & because it is not connected to anything, the data bits are falling out the end all over your desk (a metaphor I hope you understand)

Thank you very much for your response.
Please, is there a way to simulate data from e.g. a temperature sensor without having (a physical sensor) and capture it (the data) on a serial port, then display it for educational purposes?

Must it be a serial port?

Not necessarily.

It is to stimulate a simple use case of IoT.

OK, so if it MUST be serial then, on windows, you can use com0com to setup a pair of virtual com ports.
e.g. virtual com 8 <- -> com 9
then you write to com 9, it appears in com 8, you respond to com 8 and the response appears on com 9

NOTE: This is by no means simple and serial devices are becoming less and less common - so in my opinion, not typical of many of todays IoT setups.


If you just want to simulate sensors, then I would recommend using MQTT (publish random sensor values over MQTT then subscribe to the same topic and then use the values on a dashboard or whatever you need to do do.)

MQTT is pretty much the defacto means of publishing IoT data at this present time.

Honestly, thank you very much for your help and your time.

I will try it all and see if I will succeed in working this.

If you want to learn more about MQTT then see this tutorial MQTT Essentials - All Core Concepts explained

Thank you very much Colin for your help.
I appreciate.

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