7-inch Industrial HMI Mainboard Reference Design
An illustrative 7-inch industrial HMI mainboard design for PLC operator panels, production-line workstation terminals, EV charger / energy-storage cabinet displays and building HVAC control panels: STM32MP135 MPU, DC 24V wide-range input, 2 × isolated RS-485, 1 × isolated CAN, Fast Ethernet and USB Host / Device, with parts selected for −20 ~ +70°C operation. This page covers the function, selection notes and available VOOHU parts for all 32 component positions on the board.
Illustrative PCB ⇄ Schematic
The illustrative layout shows placement and component positions; click any position to see its selection notes, recommended parts and package. The board view is an illustration neatly arranged by functional zone (not the actual layout); external interfaces sit along the bottom edge, and the LCD / touch flex cables leave from the top edge.
The two RS-485 channels are identical (U4 / J1 and U5 / J2); only one is drawn. The incoming lines pass the GDT (stage-1 discharge to chassis ground), the bidirectional ESD (stage-2 clamp) and the 4532 signal-line common-mode choke before reaching the isolated RS-485 transceiver, whose isolated side is powered by the push-pull isolated supply (ISO 5V). The GDT is a 2-pole part, one per port; to discharge both A and B to ground at the same time, use the 3-pole common-ground WHGT090V1P0A instead. Termination and bias resistor values depend on your design.
Board bill of materials
Click any row to jump to that position and view its selection notes
| No. | Zone | Position | Ref. | VOOHU category | Recommended part | Availability |
|---|---|---|---|---|---|---|
| 01 | A Fieldbus | Bus terminals (485-1 / 485-2 / CAN) | J1 J2 J3 | — | — | Non-VOOHU |
| 02 | A Fieldbus | Gas discharge tube (stage 1) | GDT1 GDT2 GDT3 | GDT | WHGD200V1P0B | VOOHU |
| 03 | A Fieldbus | Bus TVS (stage-2 clamp) | D1 D2 D3 | TVS / ESD | WHALD30E2B | VOOHU |
| 04 | A Fieldbus | Bus differential-line common-mode choke | L1 L2 L3 | Signal Line CMC | WHAC-4532A-601T0 | VOOHU |
| 05 | A Fieldbus | Isolated RS-485 transceiver ×2 | U4 U5 | — | — | Non-VOOHU |
| 06 | A Fieldbus | Isolated CAN transceiver | U6 | — | — | Non-VOOHU |
| 07 | B Ethernet | RJ45 port (with LEDs) | J4 | RJ45 Connectors | SYT561188AB1A1DB4 | VOOHU |
| 08 | B Ethernet | 10/100 LAN transformer | T1 | 10/100 LAN Transformers | WHS16037TG | VOOHU |
| 09 | B Ethernet | Ethernet ESD array | D4 | TVS / ESD | WHALD03G4U | VOOHU |
| 10 | B Ethernet | 10/100 PHY (RMII) | U7 | Ethernet PHY | JL1101BR-NI | VOOHU |
| 11 | B Ethernet | PHY 25MHz crystal | Y3 | — | — | Non-VOOHU |
| 12 | C USB · Storage | USB 2.0 Type-A receptacle (Host) | J5 | — | — | Non-VOOHU |
| 13 | C USB · Storage | USB Type-C receptacle (Device, USB 2.0 only) | J6 | USB / Type-C | WHTCAX01167303 | VOOHU |
| 14 | C USB · Storage | USB ESD array ×2 | D5 D6 | TVS / ESD | WHTA5V01P2C | VOOHU |
| 15 | C USB · Storage | USB signal-line common-mode choke ×2 | L4 L5 | Signal Line CMC | WHAC-2012A-900T0 | VOOHU |
| 16 | C USB · Storage | microSD card socket | J7 | SD Card Sockets | WHTF190T123101W | VOOHU |
| 17 | D Core | STM32MP135 MPU | U1 | — | STM32MP135FAF7 | Non-VOOHU |
| 18 | D Core | DDR3L memory | U2 | — | — | Non-VOOHU |
| 19 | D Core | eMMC / QSPI Flash | U3 | — | — | Non-VOOHU |
| 20 | D Core | Main crystals 24MHz + 32.768kHz | Y1 Y2 | — | — | Non-VOOHU |
| 21 | D Core | Core-supply filter molded inductor | L6 L7 | Molded Inductors | WHYTA0420 Series | VOOHU |
| 22 | E Display & touch | LCD FPC connector (RGB 24-bit, 40P) | J8 | — | — | Non-VOOHU |
| 23 | E Display & touch | Touch FPC connector (I²C, 6P) | J9 | — | — | Non-VOOHU |
| 24 | E Display & touch | Backlight boost inductor | L8 | Molded Inductors | WHYT0630 Series | VOOHU |
| 25 | E Display & touch | Backlight boost driver | U8 | — | — | Non-VOOHU |
| 26 | F Power | DC 24V input terminal | J10 | — | — | Non-VOOHU |
| 27 | F Power | Input fuse + TVS | F1 D7 | TVS / ESD | WHTB058VA | VOOHU |
| 28 | F Power | Power line common-mode choke (EMI) | L9 | Power Line CMC | WHAL-7060A-102T0 | VOOHU |
| 29 | F Power | Synchronous buck ×2 (24V→5V→3.3V) | U9 U10 | — | — | Non-VOOHU |
| 30 | F Power | DC-DC molded inductor ×2 | L10 L11 | Molded Inductors | WHYT0630 Series | VOOHU |
| 31 | F Power | Push-pull isolated power transformer | T2 | Push-Pull Transformers | WHST06K14A0 | VOOHU |
| 32 | F Power | Push-pull driver + isolated-side LDO | U11 U12 | — | — | Non-VOOHU |
Resources & downloads
Board bill of materials
Reference designators, zones, VOOHU categories, recommended parts and availability for all 32 positions. Opens directly in Excel.
Datasheet collection
Datasheet PDFs for the VOOHU parts recommended on this board.
Design files & footprint library
Schematic, PCB, and VOOHU part footprints and 3D models.
Coming soonRequest the HMI reference design full package
Includes the full-board BOM, datasheets for the recommended VOOHU parts and position-by-position selection notes. For selection advice tailored to your bus count, screen size or power supply, please include it in your requirements. We reply within 24 hours on working days.
