# Ignition can't connect to ModBus RTU device **URL:** \ **Category:** Ignition\ **Tags:** modbus\ **Created:** [May 23, 2024, 5:56pm UTC](https://forum.inductiveautomation.com/t/ignition-cant-connect-to-modbus-rtu-device/90823 "2024-05-23T17:56:08Z")\ **Posts on this page:** 7\ **Page:** 1
**Author:** ![SMarcin](https://avatars.discourse-cdn.com/v4/letter/s/8e8cbc/32.png) [@SMarcin](https://forum.inductiveautomation.com/u/SMarcin)\ **Post date:** [May 23, 2024, 5:56pm UTC](https://forum.inductiveautomation.com/t/ignition-cant-connect-to-modbus-rtu-device/90823/1 "2024-05-23T17:56:09Z")
Hello, I have setup a ModbusRTU connection via RS232 which is valid since i am able to read the values from the device using qModMaster, but Ignition doesnt connect to it - status changes from Disconnected to Connecting and back to Disconnected. I am using one of those converters: _Teyleten Robot USB to RS485 485 Converter Adapter CH340T Chip_ ![71a8d6DoqrL.AC_SX466](https://us1.discourse-cdn.com/inductiveautomation/original/3X/4/b/4b44d1b8691c2034b5228a47a508f427cada422a.jpeg) My settings (sorry for poor quality, i had to improvise): ![set1](https://us1.discourse-cdn.com/inductiveautomation/original/3X/3/8/382d81dea665fab6ebf96729f67fefcd7dff927c.jpeg) ![IMG_0025](https://us1.discourse-cdn.com/inductiveautomation/original/3X/0/a/0ae8dbeb2aa3f0969f6e57a1b1bcfbe7c36bada8.jpeg) Dont mind the toggled RS-485 mode, i toggled it just to check it out since i had no other idea. ---
**Author:** ![Kevin.Herron](https://sea1.discourse-cdn.com/inductiveautomation/user_avatar/forum.inductiveautomation.com/kevin.herron/32/7259_2.png) [@Kevin.Herron](https://forum.inductiveautomation.com/u/Kevin.Herron)\ **Post date:** [May 23, 2024, 5:57pm UTC](https://forum.inductiveautomation.com/t/ignition-cant-connect-to-modbus-rtu-device/90823/2 "2024-05-23T17:57:23Z")
What have you tried? What's in the logs? Is the device status "Connected"? What address / OPC Item Path are you trying to read? ---
**Author:** ![SMarcin](https://avatars.discourse-cdn.com/v4/letter/s/8e8cbc/32.png) [@SMarcin](https://forum.inductiveautomation.com/u/SMarcin)\ **Post date:** [May 23, 2024, 6:10pm UTC](https://forum.inductiveautomation.com/t/ignition-cant-connect-to-modbus-rtu-device/90823/3 "2024-05-23T18:10:26Z")
Since im new to Ignition, i`ll have to say that i dont know how to check the logs. Device status was changing all the time: Disconnected - Connecting - Disconnected again. I wasnt trying any specific addresses, since i couldnt connect to the device at all. But as i said, i was able to connect to the device via qModMaster. ---
**Author:** ![Kevin.Herron](https://sea1.discourse-cdn.com/inductiveautomation/user_avatar/forum.inductiveautomation.com/kevin.herron/32/7259_2.png) [@Kevin.Herron](https://forum.inductiveautomation.com/u/Kevin.Herron)\ **Post date:** [May 23, 2024, 6:13pm UTC](https://forum.inductiveautomation.com/t/ignition-cant-connect-to-modbus-rtu-device/90823/4 "2024-05-23T18:13:27Z")
Not being able to "connect" with Modbus RTU means not being able to open the serial port. Usually this means you have it configured incorrectly (wrong COM port, etc...), or don't have permission, or something else already has that port open. > [@SMarcin](#): > > Since im new to Ignition, i`ll have to say that i dont know how to check the logs. Probably best bet is to call support and let them help you. ---
**Author:** ![SMarcin](https://avatars.discourse-cdn.com/v4/letter/s/8e8cbc/32.png) [@SMarcin](https://forum.inductiveautomation.com/u/SMarcin)\ **Post date:** [May 23, 2024, 9:45pm UTC](https://forum.inductiveautomation.com/t/ignition-cant-connect-to-modbus-rtu-device/90823/5 "2024-05-23T21:45:08Z")
I'd assume its because of the ch340 drivers maybe? ---
**Author:** ![pturmel](https://sea1.discourse-cdn.com/inductiveautomation/user_avatar/forum.inductiveautomation.com/pturmel/32/3295_2.png) [@pturmel](https://forum.inductiveautomation.com/u/pturmel)\ **Post date:** [May 23, 2024, 9:57pm UTC](https://forum.inductiveautomation.com/t/ignition-cant-connect-to-modbus-rtu-device/90823/6 "2024-05-23T21:57:50Z")
If you must use a USB-to-Serial interface, you will have best results with those built with an FTDI chipset. ---
**Author:** ![SMarcin](https://avatars.discourse-cdn.com/v4/letter/s/8e8cbc/32.png) [@SMarcin](https://forum.inductiveautomation.com/u/SMarcin)\ **Post date:** [May 25, 2024, 7:55pm UTC](https://forum.inductiveautomation.com/t/ignition-cant-connect-to-modbus-rtu-device/90823/7 "2024-05-25T19:55:18Z")
I will try it out and post the results.