# Send data using WLAN from Serial control node (ttyUSB0) from Raspberry Pi Zero W to a Raspberry Pi 4B

**URL:** <https://discourse.nodered.org/t/send-data-using-wlan-from-serial-control-node-ttyusb0-from-raspberry-pi-zero-w-to-a-raspberry-pi-4b/101125>\
**Category:** General\
**Created:** [24 May 2026 11:13 UTC](https://discourse.nodered.org/t/send-data-using-wlan-from-serial-control-node-ttyusb0-from-raspberry-pi-zero-w-to-a-raspberry-pi-4b/101125 "2026-05-24T11:13:45Z")\
**Posts on this page:** 7\
**Page:** 2

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**Author:** ![dynamicdave](https://sea2.discourse-cdn.com/flex026/user_avatar/discourse.nodered.org/dynamicdave/32/96_2.png) [@dynamicdave](https://discourse.nodered.org/u/dynamicdave)\
**Post date:** [5 June 2026 14:55 UTC](https://discourse.nodered.org/t/send-data-using-wlan-from-serial-control-node-ttyusb0-from-raspberry-pi-zero-w-to-a-raspberry-pi-4b/101125/21 "2026-06-05T14:55:31Z")

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I'm not sure why you are using `Dynamic Subscription`.  
Try changing the `Action` to `Subscribe to single topic` and enter `homeassistant/sensor/#` as the topic in the MQTT-In node ?

**Edit:** Just checking - are you using HomeAssistant rather than Node-RED

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**Author:** ![TotallyInformation](https://sea2.discourse-cdn.com/flex026/user_avatar/discourse.nodered.org/totallyinformation/32/31_2.png) [@TotallyInformation](https://discourse.nodered.org/u/TotallyInformation)\
**Post date:** [5 June 2026 15:51 UTC](https://discourse.nodered.org/t/send-data-using-wlan-from-serial-control-node-ttyusb0-from-raspberry-pi-zero-w-to-a-raspberry-pi-4b/101125/22 "2026-06-05T15:51:14Z")

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> [@nosered1966](#):
>
> Do you have any ideas?

The broker and Node-RED are on the same Pi aren't they? If so, the broker's address in Node-RED is `localhost:1883` or `127.0.0.1:1883`.

Using a `192.168.*` address forces Node-RED to try to go _out_ to your LAN, through the router to find the right place - back on the Pi. Not what you want.

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**Author:** ![nosered1966](https://sea2.discourse-cdn.com/flex026/user_avatar/discourse.nodered.org/nosered1966/32/52859_2.png) [@nosered1966](https://discourse.nodered.org/u/nosered1966)\
**Post date:** [5 June 2026 16:57 UTC](https://discourse.nodered.org/t/send-data-using-wlan-from-serial-control-node-ttyusb0-from-raspberry-pi-zero-w-to-a-raspberry-pi-4b/101125/23 "2026-06-05T16:57:52Z")

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@dynamicdave @TotallyInformation

All clear – everything is working as it should!

I didn't understand, that it is important that a MQTT client has to subscribe to the topics of messages and that the `'#'` in `mosquitto_sub -v -t '#'` is a wildcard for all topics, why it worked in the SSH but not in Node-Red.

After setting the correct topic / using the wildcard in the mqtt in node, it works perfectly:

 ![image](https://us1.discourse-cdn.com/flex026/uploads/nodered/original/3X/1/a/1a2e2a7df62444bfeb43bc9b720d1331bfdfe602.png)

Thank you so much for your help!!!

**==================================================================**

Would you still be willing to help me read data via the serial interface?  
I reckon I’ll need to use the following device on the ESP32 for this.  
But the first question is:  
Which micro-USB port should I connect my USB-to-serial adapter to, and  
which serial port should I select for this?

 ![image](https://us1.discourse-cdn.com/flex026/uploads/nodered/original/3X/6/4/649a0a64dd8e09c9598cdd30ca8d0815ed690469.png)

The documentation for the [ESP32-S2-DevKitC-1](https://docs.espressif.com/projects/esp-dev-kits/en/latest/esp32s2/esp32-s2-devkitc-1/user_guide.html#id3) provides the following information:

 ![image](https://us1.discourse-cdn.com/flex026/uploads/nodered/original/3X/2/5/256e63b4df3803fed4e841d83ad82706564fadff.jpeg)

**ESP32-S2 USB Port**  
ESP32-S2 full-speed USB OTG interface, compliant with the USB 1.1 specifications. The interface is used for power supply to the board, for flashing applications to the chip, and for communication with the chip using USB 1.1 protocols.

**USB-to-UART Port**  
A Micro-USB port used for power supply to the board, for flashing applications to the chip, as well as the communication with the chip via the on-board USB-to-UART bridge.

**USB-to-UART Bridge**  
Single USB-to-UART bridge chip provides transfer rates up to 3 Mbps.

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<div class="post-metadata">

**Author:** ![TotallyInformation](https://sea2.discourse-cdn.com/flex026/user_avatar/discourse.nodered.org/totallyinformation/32/31_2.png) [@TotallyInformation](https://discourse.nodered.org/u/TotallyInformation)\
**Post date:** [5 June 2026 19:10 UTC](https://discourse.nodered.org/t/send-data-using-wlan-from-serial-control-node-ttyusb0-from-raspberry-pi-zero-w-to-a-raspberry-pi-4b/101125/24 "2026-06-05T19:10:17Z")

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I've not used that model but I would imagine either Serial 0 or Serial 1.

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**Author:** ![dynamicdave](https://sea2.discourse-cdn.com/flex026/user_avatar/discourse.nodered.org/dynamicdave/32/96_2.png) [@dynamicdave](https://discourse.nodered.org/u/dynamicdave)\
**Post date:** [5 June 2026 20:01 UTC](https://discourse.nodered.org/t/send-data-using-wlan-from-serial-control-node-ttyusb0-from-raspberry-pi-zero-w-to-a-raspberry-pi-4b/101125/25 "2026-06-05T20:01:15Z")

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I reckon you need to use the pins on the chip - NOT the USB sockets.  
The pinouts for the ESP32 show 3 UART controllers.  
GPIO43 and GPIO44 look like suitable candidates to try.

 ![DevKit](https://us1.discourse-cdn.com/flex026/uploads/nodered/original/3X/c/5/c59f6b1585525c503a9a67b1fea10f79a2261663.jpeg)  
 ![DevKit_UART](https://us1.discourse-cdn.com/flex026/uploads/nodered/original/3X/4/2/422d0b87d9b97a1bc4754ebdb0509f9e38ba6152.jpeg)  
Like @TotallyInformation I've not used that particular device - looks like it has many, many pins.

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<div class="post-metadata">

**Author:** ![TotallyInformation](https://sea2.discourse-cdn.com/flex026/user_avatar/discourse.nodered.org/totallyinformation/32/31_2.png) [@TotallyInformation](https://discourse.nodered.org/u/TotallyInformation)\
**Post date:** [5 June 2026 20:22 UTC](https://discourse.nodered.org/t/send-data-using-wlan-from-serial-control-node-ttyusb0-from-raspberry-pi-zero-w-to-a-raspberry-pi-4b/101125/26 "2026-06-05T20:22:28Z")

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> [@dynamicdave](#):
>
> I reckon you need to use the pins on the chip - NOT the USB sockets.

I wasn't sure about that. The doc seems to suggest that you can use them:

> [@nosered1966](#):
>
> for communication with the chip using USB 1.1 protocols

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**Author:** ![system](https://us1.discourse-cdn.com/flex026/uploads/nodered/original/1X/d073cd938eafa2e558d7c2cd59003b3ef4963033.png) [@system](https://discourse.nodered.org/u/system)\
**Post date:** [3 September 2026 20:23 UTC](https://discourse.nodered.org/t/send-data-using-wlan-from-serial-control-node-ttyusb0-from-raspberry-pi-zero-w-to-a-raspberry-pi-4b/101125/27 "2026-09-03T20:23:07Z")

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