--- title: Adding Sub-Panels description: mercury,sub-panel,subpanel,discover bus,mr52,mr16in,mr16out,rs-485 --- [Skip to content](https://help.alocity.com/knowledge/mercury-adding-sub-panels#main-content) English Show submenu for translations [SUBMIT A TICKET HERE](https://help.alocity.com/knowledge/kb-tickets/new?hsLang=en) [![Alocity](https://help.alocity.com/hs-fs/hubfs/alocity-logo%20Full.png?width=181&height=48&name=alocity-logo%20Full.png)](https://www.alocity.com/) Open main navigation Close main navigation - English Show submenu for translations - [SUBMIT A TICKET HERE](https://help.alocity.com/knowledge/kb-tickets/new) - [Contact Support Now](mailto:support@alocity.com) [Contact Support Now](mailto:support@alocity.com) Hello. How can we help you? - There are no suggestions because the search field is empty. 1. [Alocity Help Center (Knowledge Base)](https://help.alocity.com/knowledge?hsLang=en) 2. [Mercury Installation, Setup And Configuration Guide](https://help.alocity.com/knowledge/mercury-installation-setup-and-configuration-guide?hsLang=en) 3. [Setup and Configuration](https://help.alocity.com/knowledge/mercury-installation-setup-and-configuration-guide?hsLang=en#setup-and-configuration) # Adding Sub-Panels ## How to Add MR52, MR16IN and MR16OUT Modules to a Mercury Controller Sub-panels are the RS-485 modules wired to a Mercury controller, such as MR52 reader interfaces and MR16IN/MR16OUT I/O boards. Add them after the controller is online. --- ### 1. Before You Start - The controller shows **Online**. See [Adding a Mercury Controller to Alocity](https://help.alocity.com/knowledge/adding-a-device-2-0?hsLang=en). - Each sub-panel is wired, terminated and powered. See [Installing Mercury Hardware](https://help.alocity.com/knowledge/mercury-panel-installation?hsLang=en). - Each sub-panel has a unique address and is set to 38,400 bps. Addresses must not overlap on the same bus. --- ### 2. Add Sub-Panels Automatically with Discover Bus 1. Go to **Hardware** › **ACUs** and click the controller's name. 2. On the **Topology** tab, click **Discover bus**. 3. The boards found on the RS-485 bus are listed. Check each board's model and address. 4. Accept the boards you want to add. 5. Check that each board appears in the board chain with a **MATCHED** badge. *![Screenshot 2026-11-05 113253](https://help.alocity.com/hs-fs/hubfs/Screenshot%202026-11-05%20113253.png?width=670&height=169&name=Screenshot%202026-11-05%20113253.png)* --- ### 3. Add a Sub-Panel Manually 1. On the **Topology** tab, click **Add subpanel**. 2. Choose the **Board model**: **MR52-S3**, **MR54-S4**, **MR16IN-S3**, **MR16OUT-S3** or **MR50-S3**. 3. Enter the **DIP address** (1–31). It must match the DIP switches on the board. 4. Click **Add**. *![Screenshot 2026-11-05 112458](https://help.alocity.com/hs-fs/hubfs/Screenshot%202026-11-05%20112458.png?width=526&height=313&name=Screenshot%202026-11-05%20112458.png)* > **Note:** The bus speed is set on the board's DIP switches, not in this dialog. Alocity's standard is 38,400 bps, shown as **BUS BAUD** on the Topology tab. --- ### 4. Check the Board Chain The Topology tab shows the bus as a chain of boards, for example MP1502-Onboard (address 0) → MR52 (address 1) → MR16OUT (address 2) → MR16IN (address 3). Each board card shows its serial number, firmware, port counts and a **MATCHED** badge when it matches the hardware. ![Screenshot 2026-11-05 113517](https://help.alocity.com/hs-fs/hubfs/Screenshot%202026-11-05%20113517.png?width=631&height=299&name=Screenshot%202026-11-05%20113517.png) Click a board to see its ports. Board actions include **Locate board**, **Change address…** and **Delete module**. #### If a sub-panel doesn't appear - Check the DIP switch address and speed, then power-cycle the board. Boards read DIP switches only at power-up. - Check TR+/TR- polarity and that termination is only at both ends of the bus. - If the board's RX LED flashes but TX doesn't, it hears the controller but isn't answering. Usually the address is wrong. - See [Adding MR52-S3 and MR52-S3B Sub Boards](https://help.alocity.com/knowledge/adding-mr52-s3-and-mr52-s3b-sub?hsLang=en) for DIP switch tables and LED meanings. 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