# MODBUS RTU connection issue

**URL:** <https://forum.inductiveautomation.com/t/modbus-rtu-connection-issue/12071>\
**Category:** Ignition\
**Created:** [August 26, 2016, 6:24pm UTC](https://forum.inductiveautomation.com/t/modbus-rtu-connection-issue/12071 "2016-08-26T18:24:13Z")\
**Posts on this page:** 3\
**Page:** 1

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**Author:** ![ksong](https://avatars.discourse-cdn.com/v4/letter/k/f6c823/32.png) [@ksong](https://forum.inductiveautomation.com/u/ksong)\
**Post date:** [August 26, 2016, 6:24pm UTC](https://forum.inductiveautomation.com/t/modbus-rtu-connection-issue/12071/1 "2016-08-26T18:24:13Z")

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Hello, everyone:  
I am new to ignition and I was trying to connect a MODBUS device on my desktop but could not connect to it. Here is my setup:

- Ignition installed on my desktop: Version 7.8.3 (b2016061017) 64 bit
- Desktop running Windows 10, 64 bit
- Module Installed: Serial Support Client 3.8.2 (b2016030813)
- Module Installed: Serial Support Gateway 3.8.2 (b2016030813)
- Connection: FTDI USB-to-RS485 cable

What I want to do is a very simple task. I want my desktop connected to a MODBUS RTU device via RS485 cable. And read real-time data using ignition in web browser like localhost:8088

Desktop PC (Ignition 7.8.3) \<-------- RS485 ------------\> MODBUS RTU Device

Here is what I did:

1. Install Serial Support Gateway and Serial Support Client modules. Then reboot my computer so I can see the MODBUS RTU type in the device window;
2. Log into Ignition, Config Tab\>\> OPC-UA Server\>\>Device, then clicked “create new Device”,
3. Select MODBUS RTU type, then type in “Serial Port” to COM5, which is the com port the FTDI USB-to-RS485 cable emulated; Set baud rate to match my Modbus RTU device, e.g. 9600, 8, N, 1 etc.
4. Click “Create New Device” button. But the device status always show “Disconnected”.

I tried unplug/plug back the USB cable, reboot computer, restart serial modules. Still shows “disconnected” in Device Status.

What steps was I missing to make it work? Any suggestions are welcome. Thanks in advance!

K.S.

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<div class="post-metadata">

**Author:** ![abishur](https://sea1.discourse-cdn.com/inductiveautomation/user_avatar/forum.inductiveautomation.com/abishur/32/9096_2.png) [@abishur](https://forum.inductiveautomation.com/u/abishur)\
**Post date:** [February 16, 2017, 3:42pm UTC](https://forum.inductiveautomation.com/t/modbus-rtu-connection-issue/12071/2 "2017-02-16T15:42:38Z")

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I know this is post is getting a little long in the teeth, but I was curious if you were ever able to get this working.

If not I’d be curious to know if you were able to connect to the PLC using a standalone modbus program.

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**Author:** ![adam.morales](https://sea1.discourse-cdn.com/inductiveautomation/user_avatar/forum.inductiveautomation.com/adam.morales/32/3405_2.png) [@adam.morales](https://forum.inductiveautomation.com/u/adam.morales)\
**Post date:** [February 17, 2017, 12:14am UTC](https://forum.inductiveautomation.com/t/modbus-rtu-connection-issue/12071/3 "2017-02-17T00:14:50Z")

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If it is still relevant, there was a bug in 7.8.3 that broke the Modbus RTU driver, which was fixed in 7.8.4.