# Modbus RTU using ch340 ttl to usb on pi 4

**URL:** <https://discourse.nodered.org/t/modbus-rtu-using-ch340-ttl-to-usb-on-pi-4/80188>\
**Category:** General\
**Tags:** modbus\
**Created:** [31 July 2023 13:26 UTC](https://discourse.nodered.org/t/modbus-rtu-using-ch340-ttl-to-usb-on-pi-4/80188 "2023-07-31T13:26:47Z")\
**Posts on this page:** 8\
**Page:** 2

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**Author:** ![issambfs1](https://avatars.discourse-cdn.com/v4/letter/i/ea666f/32.png) [@issambfs1](https://discourse.nodered.org/u/issambfs1)\
**Post date:** [31 July 2023 16:16 UTC](https://discourse.nodered.org/t/modbus-rtu-using-ch340-ttl-to-usb-on-pi-4/80188/21 "2023-07-31T16:16:15Z")

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leopard@raspberrypi:~ $ groups  
leopard adm dialout cdrom sudo audio video plugdev games users input render netdev lpadmin gpio i2c spi

also i did full update&upgrade

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**Author:** ![issambfs1](https://avatars.discourse-cdn.com/v4/letter/i/ea666f/32.png) [@issambfs1](https://discourse.nodered.org/u/issambfs1)\
**Post date:** [31 July 2023 16:24 UTC](https://discourse.nodered.org/t/modbus-rtu-using-ch340-ttl-to-usb-on-pi-4/80188/22 "2023-07-31T16:24:47Z")

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![1](https://us1.discourse-cdn.com/flex026/uploads/nodered/original/3X/9/7/97a3acfef8f29fbb71922d2236b08a638db16e39.png)  
 ![2](https://us1.discourse-cdn.com/flex026/uploads/nodered/original/3X/d/c/dcbd2a4f665772e1200baa0c484cbf49cb2dcc72.png)

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**Author:** ![issambfs1](https://avatars.discourse-cdn.com/v4/letter/i/ea666f/32.png) [@issambfs1](https://discourse.nodered.org/u/issambfs1)\
**Post date:** [31 July 2023 16:26 UTC](https://discourse.nodered.org/t/modbus-rtu-using-ch340-ttl-to-usb-on-pi-4/80188/23 "2023-07-31T16:26:08Z")

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after i select the show errors of node that is the output of it "Modbus Failure On State sending Get More About It By Logging"

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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:** [31 July 2023 16:33 UTC](https://discourse.nodered.org/t/modbus-rtu-using-ch340-ttl-to-usb-on-pi-4/80188/24 "2023-07-31T16:33:04Z")

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When do you see the connected and reconnecting status?

You might be better to use the modbus getter or flex getter rather than the read node. Then you can trigger when you want to get data, and it can be easier to analyse when it does not work. I assume that you only have one modbus read node.

The groups look ok.

> [@issambfs1](#):
>
> also i did full update&upgrade

I presume you mean update and full-upgrade.

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<div class="post-metadata">

**Author:** ![issambfs1](https://avatars.discourse-cdn.com/v4/letter/i/ea666f/32.png) [@issambfs1](https://discourse.nodered.org/u/issambfs1)\
**Post date:** [31 July 2023 20:04 UTC](https://discourse.nodered.org/t/modbus-rtu-using-ch340-ttl-to-usb-on-pi-4/80188/25 "2023-07-31T20:04:20Z")

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sudo nano /boot/cmdline.txt  
can this effect on it

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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:** [31 July 2023 20:16 UTC](https://discourse.nodered.org/t/modbus-rtu-using-ch340-ttl-to-usb-on-pi-4/80188/26 "2023-07-31T20:16:12Z")

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I don't know, but I do know that once again you have not answered the questions. There is no point me trying to help if you don't answer questions.

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**Author:** ![issambfs1](https://avatars.discourse-cdn.com/v4/letter/i/ea666f/32.png) [@issambfs1](https://discourse.nodered.org/u/issambfs1)\
**Post date:** [4 August 2023 16:23 UTC](https://discourse.nodered.org/t/modbus-rtu-using-ch340-ttl-to-usb-on-pi-4/80188/27 "2023-08-04T16:23:27Z")

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i fix my problem by upgrade the system raspberry os From 32bit to 64bit !

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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:** [18 August 2023 16:24 UTC](https://discourse.nodered.org/t/modbus-rtu-using-ch340-ttl-to-usb-on-pi-4/80188/28 "2023-08-18T16:24:15Z")

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