# HMI Modbus breakdown help **URL:** \ **Category:** Ignition\ **Tags:** vision\ **Created:** [April 24, 2025, 9:33pm UTC](https://forum.inductiveautomation.com/t/hmi-modbus-breakdown-help/105541 "2025-04-24T21:33:49Z")\ **Posts on this page:** 9\ **Page:** 1
**Author:** ![Edmund\_Mayer](https://avatars.discourse-cdn.com/v4/letter/e/87869e/32.png) [@Edmund\_Mayer](https://forum.inductiveautomation.com/u/Edmund_Mayer)\ **Post date:** [April 24, 2025, 9:33pm UTC](https://forum.inductiveautomation.com/t/hmi-modbus-breakdown-help/105541/1 "2025-04-24T21:33:49Z")
I have to update an old HMI to Ignition. The old tags in the HMI are ModBus RTU using serial port COM1, 9600 bit rate, even parity, and stopbit1. Sample tags are MBUS\14$0571 and MBUS\14$10060 and these go to on/off buttons. This is what is under the old HMI tag. I cant find any information on a breakdown on what is what. When i put wright the tag ad [MBUS]14.HR0571 as an int or like [MBUS]14.C0571 as a Boolean it says bad value. any and all help appreciated. I don't know what the plc is that it is communicating with. all i know is all the tags are for buttons so they would be writing to the plc a 1 or 0. ---
**Author:** ![ryan.white](https://sea1.discourse-cdn.com/inductiveautomation/user_avatar/forum.inductiveautomation.com/ryan.white/32/73193_2.png) [@ryan.white](https://forum.inductiveautomation.com/u/ryan.white)\ **Post date:** [April 24, 2025, 9:44pm UTC](https://forum.inductiveautomation.com/t/hmi-modbus-breakdown-help/105541/2 "2025-04-24T21:44:10Z")
How is the device connection configured on your gateway? Which device driver are you using? Do you have a license for the Serial Module? (This is required if you are using the Modbus RTU driver on Ignition version 8.1.19 or earlier) Is the PLC connected to your gateway or to the device that the vision client is on? For the gateway to be able to talk to it the PLC needs to be connected to the gateway. What have you tried so far for troubleshooting? Is the PLC listing as connected in your list of devices on the gateway? Any errors in your gateway logs? ---
**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:** [April 24, 2025, 9:49pm UTC](https://forum.inductiveautomation.com/t/hmi-modbus-breakdown-help/105541/3 "2025-04-24T21:49:51Z")
> [@ryan.white](#): > > Do you have a license for the Serial Module? (This is required if you are using the Modbus RTU driver) It's not any more. Once upon a time this was true, but not in recent versions. ---
**Author:** ![Edmund\_Mayer](https://avatars.discourse-cdn.com/v4/letter/e/87869e/32.png) [@Edmund\_Mayer](https://forum.inductiveautomation.com/u/Edmund_Mayer)\ **Post date:** [April 24, 2025, 10:34pm UTC](https://forum.inductiveautomation.com/t/hmi-modbus-breakdown-help/105541/4 "2025-04-24T22:34:53Z")
The new version of ignition you don't need a license. and I am trying to set up my ignition screens and tags to look in the same location in the plc as the old HMI. i don't have the plc connected but on my opc server i do have the device and and the same parameters set up as the old one did. what i need to know is how to decipher the old tag and turn it into an ignition tag. ---
**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:** [April 24, 2025, 10:42pm UTC](https://forum.inductiveautomation.com/t/hmi-modbus-breakdown-help/105541/5 "2025-04-24T22:42:32Z")
> [@Edmund\_Mayer](#): > > what i need to know is how to decipher the old tag and turn it into an ignition tag. If you can't tell us anything about this HMI hardware / software then we're just guessing as much as you are. ---
**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:** [April 24, 2025, 10:45pm UTC](https://forum.inductiveautomation.com/t/hmi-modbus-breakdown-help/105541/6 "2025-04-24T22:45:20Z")
> [@Edmund\_Mayer](#): > > When i put wright the tag ad [MBUS]14.HR0571 as an int or like [MBUS]14.C0571 as a Boolean it says bad value. > [@Edmund\_Mayer](#): > > i don't have the plc connected As is to be expected then... ---
**Author:** ![Edmund\_Mayer](https://avatars.discourse-cdn.com/v4/letter/e/87869e/32.png) [@Edmund\_Mayer](https://forum.inductiveautomation.com/u/Edmund_Mayer)\ **Post date:** [April 24, 2025, 11:31pm UTC](https://forum.inductiveautomation.com/t/hmi-modbus-breakdown-help/105541/7 "2025-04-24T23:31:38Z")
sorry i forgot to add that information. it is a parker model: PA210T-133 serial: 140515R0059. and i thought it not being connected was that reason but I'm not sure how i should tag these buttons. if i should use [MBUS]14.HR0571 as an int or [MBUS]14.C0571 as a bool. I'm not sure how ignition writes to the tag in each case. ---
**Author:** ![ryan.white](https://sea1.discourse-cdn.com/inductiveautomation/user_avatar/forum.inductiveautomation.com/ryan.white/32/73193_2.png) [@ryan.white](https://forum.inductiveautomation.com/u/ryan.white)\ **Post date:** [April 25, 2025, 2:49am UTC](https://forum.inductiveautomation.com/t/hmi-modbus-breakdown-help/105541/8 "2025-04-25T02:49:36Z")
> [@Edmund\_Mayer](#): > > MBUS]14.C0571 as a bool. This is likely the correct method for these, if they are being treated as a bool in the original HMI. The original address seems to indicate that they are coils. ---
**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:** [April 25, 2025, 12:31pm UTC](https://forum.inductiveautomation.com/t/hmi-modbus-breakdown-help/105541/9 "2025-04-25T12:31:53Z")
> [@Edmund\_Mayer](#): > > not sure how i should tag these buttons Be aware you cannot use the OPC Item Paths directly in buttons. Buttons needs Ignition tags. So make Ignition OPC tags, with whatever names will be meaningful to you, to point at the OPC Item Paths you determine you need.