# Serial port will not work with cable already plugged in

**URL:** <https://discourse.nodered.org/t/serial-port-will-not-work-with-cable-already-plugged-in/1560>\
**Category:** General\
**Created:** [13 July 2018 16:15 UTC](https://discourse.nodered.org/t/serial-port-will-not-work-with-cable-already-plugged-in/1560 "2018-07-13T16:15:13Z")\
**Posts on this page:** 14\
**Page:** 2

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**Author:** ![willemx](https://avatars.discourse-cdn.com/v4/letter/w/a4c791/32.png) [@willemx](https://discourse.nodered.org/u/willemx)\
**Post date:** [17 July 2018 20:10 UTC](https://discourse.nodered.org/t/serial-port-will-not-work-with-cable-already-plugged-in/1560/21 "2018-07-17T20:10:01Z")

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The serial node is configured as `/dev/ttyUSB0:115200-8N1`

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**Author:** ![Colin](https://sea2.discourse-cdn.com/flex026/user_avatar/discourse.nodered.org/colin/32/17040_2.png) [@Colin](https://discourse.nodered.org/u/Colin)\
**Post date:** [17 July 2018 20:32 UTC](https://discourse.nodered.org/t/serial-port-will-not-work-with-cable-already-plugged-in/1560/22 "2018-07-17T20:32:15Z")

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And the rest of the serial node config?

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**Author:** ![willemx](https://avatars.discourse-cdn.com/v4/letter/w/a4c791/32.png) [@willemx](https://discourse.nodered.org/u/willemx)\
**Post date:** [18 July 2018 08:11 UTC](https://discourse.nodered.org/t/serial-port-will-not-work-with-cable-already-plugged-in/1560/23 "2018-07-18T08:11:00Z")

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Input:

```auto
Split input on the character \n
and deliver ascii strings

```

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**Author:** ![markost](https://avatars.discourse-cdn.com/v4/letter/m/3d9bf3/32.png) [@markost](https://discourse.nodered.org/u/markost)\
**Post date:** [18 July 2018 08:31 UTC](https://discourse.nodered.org/t/serial-port-will-not-work-with-cable-already-plugged-in/1560/24 "2018-07-18T08:31:22Z")

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Do you know what is USB/serial chip is in your device?

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**Author:** ![willemx](https://avatars.discourse-cdn.com/v4/letter/w/a4c791/32.png) [@willemx](https://discourse.nodered.org/u/willemx)\
**Post date:** [18 July 2018 09:04 UTC](https://discourse.nodered.org/t/serial-port-will-not-work-with-cable-already-plugged-in/1560/25 "2018-07-18T09:04:47Z")

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Chip: FT232R (see: [https://www.sossolutions.nl/slimme-meter-kabel](https://www.sossolutions.nl/slimme-meter-kabel))

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**Author:** ![markost](https://avatars.discourse-cdn.com/v4/letter/m/3d9bf3/32.png) [@markost](https://discourse.nodered.org/u/markost)\
**Post date:** [18 July 2018 09:20 UTC](https://discourse.nodered.org/t/serial-port-will-not-work-with-cable-already-plugged-in/1560/26 "2018-07-18T09:20:27Z")

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Ok,  
is it possible to try with cp2102 or ch340g chip?

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<div class="post-metadata">

**Author:** ![willemx](https://avatars.discourse-cdn.com/v4/letter/w/a4c791/32.png) [@willemx](https://discourse.nodered.org/u/willemx)\
**Post date:** [18 July 2018 11:17 UTC](https://discourse.nodered.org/t/serial-port-will-not-work-with-cable-already-plugged-in/1560/27 "2018-07-18T11:17:17Z")

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No sorry, this is my only serial device...

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<div class="post-metadata">

**Author:** ![markost](https://avatars.discourse-cdn.com/v4/letter/m/3d9bf3/32.png) [@markost](https://discourse.nodered.org/u/markost)\
**Post date:** [18 July 2018 18:00 UTC](https://discourse.nodered.org/t/serial-port-will-not-work-with-cable-already-plugged-in/1560/28 "2018-07-18T18:00:43Z")

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My idea is to try some other usb/serial chip.  
Cp2012 and ch340g are about 1-2 USD/each.  
You need just connect tx to rx on the module. On the node-red take inject node and set to send anything every few second to the usb port.

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**Author:** ![Colin](https://sea2.discourse-cdn.com/flex026/user_avatar/discourse.nodered.org/colin/32/17040_2.png) [@Colin](https://discourse.nodered.org/u/Colin)\
**Post date:** [19 July 2018 08:04 UTC](https://discourse.nodered.org/t/serial-port-will-not-work-with-cable-already-plugged-in/1560/29 "2018-07-19T08:04:04Z")

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> [@willemx](#):
>
> Split input on the character \n and deliver ascii strings

Try it with a fixed number of characters instead, in order to see whether anything at all is being received. Perhaps it is not syncing correctly on startup or something.

When you run cu does the node-red log show anything (in both working and non-working cases)?

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**Author:** ![dceejay](https://sea2.discourse-cdn.com/flex026/user_avatar/discourse.nodered.org/dceejay/32/38_2.png) [@dceejay](https://discourse.nodered.org/u/dceejay)\
**Post date:** [19 July 2018 08:31 UTC](https://discourse.nodered.org/t/serial-port-will-not-work-with-cable-already-plugged-in/1560/30 "2018-07-19T08:31:20Z")

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this is still very odd - I have several FTDI based devices - GPS, cable to Arduino etc... and so far I can't provoke this behaviour at all.

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<div class="post-metadata">

**Author:** ![willemx](https://avatars.discourse-cdn.com/v4/letter/w/a4c791/32.png) [@willemx](https://discourse.nodered.org/u/willemx)\
**Post date:** [19 July 2018 11:04 UTC](https://discourse.nodered.org/t/serial-port-will-not-work-with-cable-already-plugged-in/1560/31 "2018-07-19T11:04:02Z")

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Starting today, I will be on vacation for a couple of weeks, so I cannot perform more tests now. I have my Pi connected to a UPS, so I hope it will keep running during my absence...  
When I return I will continue to investigate this problem.  
Thanks everyone for your help so far!

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**Author:** ![asandford](https://avatars.discourse-cdn.com/v4/letter/a/eb8c5e/32.png) [@asandford](https://discourse.nodered.org/u/asandford)\
**Post date:** [19 July 2018 23:19 UTC](https://discourse.nodered.org/t/serial-port-will-not-work-with-cable-already-plugged-in/1560/32 "2018-07-19T23:19:18Z")

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This has been reported on the Raspi boards here [https://www.raspberrypi.org/forums/viewtopic.php?f=31&t=213230&hilit=ftdi](https://www.raspberrypi.org/forums/viewtopic.php?f=31&t=213230&hilit=ftdi)

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<div class="post-metadata">

**Author:** ![Colin](https://sea2.discourse-cdn.com/flex026/user_avatar/discourse.nodered.org/colin/32/17040_2.png) [@Colin](https://discourse.nodered.org/u/Colin)\
**Post date:** [20 July 2018 16:05 UTC](https://discourse.nodered.org/t/serial-port-will-not-work-with-cable-already-plugged-in/1560/33 "2018-07-20T16:05:04Z")

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> [@asandford](#):
>
> This has been reported on the Raspi boards here [https://www.raspberrypi.org/forums/viewtopic.php?f=31&t=213230&hilit=ftdi](https://www.raspberrypi.org/forums/viewtopic.php?f=31&t=213230&hilit=ftdi)

That is not the same problem is it? That is describing a situation where the port is not recognised at all on boot. In the case here it works fine using cu but not in node-red. If it were the linked problem then cu would not work either would it?

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<div class="post-metadata">

**Author:** ![asandford](https://avatars.discourse-cdn.com/v4/letter/a/eb8c5e/32.png) [@asandford](https://discourse.nodered.org/u/asandford)\
**Post date:** [21 July 2018 19:13 UTC](https://discourse.nodered.org/t/serial-port-will-not-work-with-cable-already-plugged-in/1560/34 "2018-07-21T19:13:31Z")

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I don't know what cu is, but FTDI devices are unstable. I have many clone arduino nanos that are now useless as they aren't recognised at boot. cu might talk to them, but that's irrelevant if NR can't

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