4 layers115 × 75 mm InduLink-485, the printed circuit board in 3D

InduLink-485

The board follows rigorous IPC (IPC-2152, IPC-2221, IPC-7351) standards, complete with galvanic isolation, industrial transient protection (TVS, Schottky, PTC Polyfuse), a wide-input step-down switching power…

Full screen GitHub .kicad_pcb

Size: 115 × 75 mm
Copper layers: 4
Thickness: 1.6 mm
Parts: 24
Nets: 24
Pads: 185
Tracks, vias: 332, 53
Routed: Yes
KiCad: KiCad 10.0 (file 20260206)
Created: 30 Aug 2026
Updated: 8 Sep 2026

Overview

InduLink-485 is an open-source printed circuit board by 8aChristian, from the 8aChristian/InduLink-485 repository on GitHub, published under the MIT licence. It is a 4-layer board of 115 × 75 mm with 24 parts on 24 nets, routed with 332 tracks and 53 vias.

It is built around the B0505S-1WR3, ESP32-S3-WROOM-1-N8R8 and MAX13487EESA+, with the SIM7080G, AP2112K-3.3TRG1 and ISO7721DWR among its other parts. Its parts include 7 ICs, 5 diodes, 4 connectors, 2 capacitors and 1 inductor. It belongs with the ESP32 boards of this library.

Main components

README

README.md

InduLink-485 | Industrial IoT Gateway & Isolated RS-485 Telemetry Node

[blocked] [blocked] [blocked] [blocked]

InduLink-485 is a rugged, industrial-grade IoT gateway and telemetry edge node designed for mission-critical industrial automation, SCADA networks, PLC monitoring, and remote field deployments. Built around the high-performance Espressif ESP32-S3 dual-core microcontroller and the SIMCom SIM7080G multi-band cellular modem, it delivers robust, isolated bidirectional RS-485 / Modbus RTU communication with dual-link connectivity over global LTE-M, NB-IoT, Wi-Fi, and Bluetooth Low Energy.

InduLink-485 3D Isometric Hardware Render
Figure 1: High-Fidelity 3D Isometric Photorealistic Render of the InduLink-485 Industrial Gateway PCBA.

📸 PCB Layer Breakdown & System Previews

The board features a high-density 4-layer architecture with dedicated signal, power, and ground planes. Below is the visual breakdown of every individual fabrication layer:

1. Top Layer (L1 - `F.Cu`) & Bottom Layer (L4 - `B.Cu`)

Layer 1: Top Copper & Silkscreen (`F.Cu`)	Layer 4: Bottom Copper & Silkscreen (`B.Cu`)

High-speed signals, 50Ω RF coplanar microstrips, Buck power loop, SMD pads	Secondary digital routing, control lines, and bottom ground shield

2. Internal Planes (L2 - `In1.Cu` GND & L3 - `In2.Cu` Power)

Layer 2: Solid Ground Plane (`In1.Cu`)	Layer 3: Power Distribution Planes (`In2.Cu`)

100% Continuous low-impedance ground reference plane (Zero slots)	Partitioned power planes (+3.8V GSM bus, +3.3V system rail, +5V_ISO)

3. Complete 4-Layer Composite & Schematic Diagram

4-Layer Multilayer X-Ray View	Complete Circuit Schematic
	📄 Download Schematic PDF
All 4 copper layers combined with Edge.Cuts & isolation barrier	Full hierarchical schematic capture with multi-domain protection

📁 3D CAD & Documentation: 3D models are available in docs/3d/InduLink-485.step and docs/3d/InduLink-485.glb. Manufacturing packages reside in fabrication/.

🏗️ System Architecture & Block Diagram

mermaid

graph TD
    subgraph Power_Stage ["⚡ Industrial Power Architecture (9V - 36V DC)"]
        VIN["DC Power In (9V - 36V, 24V Typ)"] --> PROT["TVS SMCJ33CA + PTC Fuse 750mA + Reverse Polarity Diode"]
        PROT --> BUCK["LMR14030 Buck Converter (3.8V / 3.5A Peak)"]
        BUCK --> LDO["AP2112K-3.3 Ultra-Low Noise LDO (3.3V / 600mA)"]
        BUCK --> POSCAP["1000uF POSCAP Polymer Buffer (GSM 2A Burst Support)"]
        BUCK --> ISODC["B0505S-1WR3 Isolated DC-DC (5V_ISO Domain)"]
    end

    subgraph Compute_RF ["🧠 Compute, Wireless & Cellular Core"]
        LDO --> ESP["ESP32-S3-WROOM-1 (Xtensa LX7 @ 240MHz, 8MB Flash/PSRAM)"]
        POSCAP --> MODEM["SIM7080G LTE-M / NB-IoT / GNSS Cellular Modem"]
        ESP <-->|UART High-Speed AT Bus| MODEM
        MODEM --> ANT_LTE["U.FL LTE-M Antenna (50Ω Coplanar)"]
        MODEM --> ANT_GNSS["U.FL GNSS Antenna (50Ω Active/Passive)"]
        ESP --> ANT_WIFI["ESP32 Integrated 2.4GHz PCB Antenna (Keep-Out Protected)"]
    end

    subgraph Isolated_Fieldbus ["🛡️ Galvanically Isolated RS-485 Fieldbus"]
        ESP <-->|Isolated TX/RX/DE Lines| ISO["TI ISO7721 High-Speed Digital Isolator (5kVrms, >8mm Creepage)"]
        ISODC --> ISO
        ISODC --> RS485_IC["MAX13487 AutoDirection RS-485 Transceiver"]
        ISO <--> RS485_IC
        RS485_IC --> ESD["Semtech SM712 Asymmetric TVS (+12V/-7V 30kV ESD)"]
        ESD --> TB_RS485["Phoenix Contact 3-Pin Terminal Block (A, B, GND_ISO)"]
    end

⚡ Technical Specifications

Parameter	Specification	Engineering Details
Input Supply Voltage	$9.0 ext{V} - 36.0 ext{V DC}$ ($24 ext{V DC}$ Nominal)	Reverse polarity diode + $33 ext{V}$ 1500W TVS (`SMCJ33CA`) + 750mA PTC fuse (`MF-MSMF075-2`)
Main Step-Down Converter	TI `LMR14030SDDAR` ($3.8 ext{V} / 3.5 ext{A}$)	High-efficiency Eco-mode buck regulator with $10\mu ext{H}$ shielded power inductor (`WE-HCI`)
Cellular Transient Buffer	$1000\mu ext{F} ext{ POSCAP } + 100\mu ext{F} ext{ MLCC}$	Ultra-low ESR ($10 ext{m}\Omega$) polymer tantalum capacitor for $<100 ext{mV}$ droop during $2 ext{A}$ LTE/GSM Tx bursts
Secondary Voltage Regulator	Diodes Inc `AP2112K-3.3` ($3.3 ext{V} / 600 ext{mA}$)	High PSRR ($55 ext{dB}$), ultra-low dropout ($250 ext{mV}$) linear regulator for low-noise MCU core
Main Processing Unit (MCU)	Espressif `ESP32-S3-WROOM-1-N8R8`	Dual-core Xtensa 32-bit LX7 @ 240MHz, 512KB SRAM, 8MB Quad SPI Flash, 8MB Octal PSRAM
Cellular & Satellite Subsystem	SIMCom `SIM7080G` Global Module	Multi-band LTE Cat-M1 (eMTC) & NB-IoT + Multi-Constellation GNSS (GPS, GLONASS, BeiDou, Galileo)
Wireless Connectivity	Wi-Fi 4 (802.11 b/g/n) & Bluetooth 5.0 (BLE)	Integrated PCB antenna with $100%$ copper-free keep-out zone on all 4 layers
Fieldbus Interface	Isolated Half-Duplex RS-485 / Modbus RTU	Maxim / ADI `MAX13487EESA+` with proprietary AutoDirection control (no software RTS/DE switching required)
Galvanic Isolation Barrier	$5000 ext{V}_ ext{rms}$ Isolation / $100 ext{kV}/\mu ext{s}$ CMTI	TI `ISO7721DWR` wide-body isolator with a $1.0 ext{mm} imes 31.0 ext{mm}$ routed slot ($>4.0 ext{mm}$ physical creepage)
Isolated Power Supply	Mornsun `B0505S-1WR3` ($1 ext{W} / 200 ext{mA}$)	$1.5 ext{kV DC}$ isolation between system ground (`GND`) and fieldbus ground (`GND_ISO`)
Operating Temperature	$-40^\circ ext{C} ext{ to } +85^\circ ext{C}$ (Industrial Grade)	All passive and active semiconductors derated $\ge 25%$ across full temperature envelope
Dimensions & Form Factor	$115.0 ext{ mm} imes 75.0 ext{ mm}$ ($R=3.0 ext{ mm}$ corners)	4x M3 plated mechanical mounting holes with $\ge 6.5 ext{mm}$ isolation keep-outs

🔬 PCB Layer Stackup & Controlled Impedance

The PCB is built on an industrial 4-Layer JLC04161H standard stackup ($1.6 ext{ mm}$ nominal thickness, $1 ext{ oz} / 35\mu ext{m}$ copper outer and inner layers):

text

========================================================================================
 Layer 1 (Top / F.Cu):        Component SMD Pads, 50Ω RF Coplanar Microstrips, Buck Power Loop
---------------------------------- Dielectric Prepreg (0.21mm, FR-4, Er=4.5) ----------------
 Layer 2 (Inner 1 / In1.Cu):  Solid Continuous Ground Plane (GND) - Zero Slots
---------------------------------- Core Dielectric (1.065mm, FR-4, Er=4.5) -----------------
 Layer 3 (Inner 2 / In2.Cu):  Power Planes & Rails (+3.8V_MODEM, +3.3V, +5V, +5V_ISO)
---------------------------------- Dielectric Prepreg (0.21mm, FR-4, Er=4.5) ----------------
 Layer 4 (Bottom / B.Cu):     Digital Control Signals & Secondary Ground Shield (B.Cu GND)
========================================================================================

IPC Net Classes & Design Rules Matrix

Net Class Name	Target Nets	Track Width	Electrical Clearance	Via Rule (Dia / Drill)	Design Standard
`Power_HighCurrent`	`VIN`, `+3.8V_MODEM`, `SW_BUCK`	$1.00 ext{ mm}$ ($40 ext{ mil}$)	$0.35 ext{ mm}$ ($14 ext{ mil}$)	$0.80 ext{ mm} / 0.40 ext{ mm}$	IPC-2152 ($\Delta T < 10^\circ ext{C} @ 3.5 ext{A}$)
`Power_Standard`	`+3.3V`, `+5V`, `+5V_ISO`	$0.50 ext{ mm}$ ($20 ext{ mil}$)	$0.25 ext{ mm}$ ($10 ext{ mil}$)	$0.60 ext{ mm} / 0.30 ext{ mm}$	IPC-2152 ($1.5 ext{A}$ rated)
`GND_Planes`	`GND`, `GND_ISO`	$0.50 ext{ mm}$ ($20 ext{ mil}$)	$0.25 ext{ mm}$ ($10 ext{ mil}$)	$0.60 ext{ mm} / 0.30 ext{ mm}$	Low-impedance stitching
`RF_50R_Coplanar`	`LTE_ANT`, `GNSS_ANT`	$0.35 ext{ mm}$ ($14 ext{ mil}$)	$0.20 ext{ mm}$ ($8 ext{ mil}$)	$0.60 ext{ mm} / 0.30 ext{ mm}$	$50,\Omega$ Coplanar Waveguide w/ Ground
`RS485_Diff`	`RS485_A`, `RS485_B`	$0.30 ext{ mm}$ ($12 ext{ mil}$)	$0.25 ext{ mm}$ (gap $0.25 ext{ mm}$)	$0.60 ext{ mm} / 0.30 ext{ mm}$	$120,\Omega$ Differential Fieldbus
`Digital_Signals`	`ESP_`, `MODEM_`, `ISO_*`	$0.20 ext{ mm}$ ($8 ext{ mil}$)	$0.20 ext{ mm}$ ($8 ext{ mil}$)	$0.60 ext{ mm} / 0.30 ext{ mm}$	High-density 3.3V logic & UARTs

📋 Comprehensive Bill of Materials (BOM)

Item	Designator	Qty	Component / Value	Manufacturer	Manufacturer Part Number (MPN)	Package	Description
1	U1	1	ESP32-S3-WROOM-1-N8R8	Espressif Systems	`ESP32-S3-WROOM-1-N8R8`	SMD-41 (18x25.5mm)	Dual-Core 240MHz MCU, Wi-Fi/BLE, 8MB Flash/PSRAM
2	U2	1	SIM7080G	SIMCom Wireless	`SIM7080G`	LGA-78 (17.6x15.7mm)	Global LTE-M / NB-IoT / GNSS Positioning Modem
3	U3	1	LMR14030SDDAR	Texas Instruments	`LMR14030SDDAR`	SOIC-8-PowerPAD	4V-40V In, 3.5A Step-Down Buck Regulator
4	U4	1	AP2112K-3.3TRG1	Diodes Incorporated	`AP2112K-3.3TRG1`	SOT-23-5	Ultra-Low Dropout 3.3V / 600mA Linear Regulator
5	U5	1	ISO7721DWR	Texas Instruments	`ISO7721DWR`	SOIC-16W (Wide Body)	5kVrms High-Speed Digital Isolator (>8.0mm Creepage)
6	U6	1	B0505S-1WR3	Mornsun	`B0505S-1WR3`	SIP-4 THT (11.6x6mm)	1W Isolated 5V-to-5V DC-DC Converter (1.5kVDC)
7	U7	1	MAX13487EESA+	Analog Devices / Maxim	`MAX13487EESA+`	SOIC-8 (3.9x4.9mm)	Half-Duplex RS-485 Transceiver w/ AutoDirection Control
8	D1	1	SMCJ33CA	Littelfuse / Vishay	`SMCJ33CA`	DO-214AB (SMC)	33V Vwm, 1500W Bidirectional TVS Surge Diode
9	D2	1	B240A	Diodes Incorporated	`B240A-13-F`	DO-214AC (SMA)	40V, 2.0A Schottky Rectifier (Low Vf = 0.50V)
10	D3	1	SM712.TCT	Semtech	`SM712.TCT`	SOT-23	Asymmetric Dual TVS (+12V/-7V) for RS-485 (30kV ESD)
11	D4, D5	2	CD0402-T05C	Bourns	`CD0402-T05C`	0402 (1005 Metric)	Ultra-Low Capacitance (0.5pF) 5V RF ESD Protection
12	F1	1	MF-MSMF075-2	Bourns	`MF-MSMF075-2`	1812 (4532 Metric)	Resettable PTC Fuse, 750mA Hold / 1.5A Trip, 30Vdc
13	C3	1	1000uF 6.3V POSCAP	Panasonic	`6TPB1000M`	EIA-7343-31 (Case D)	Polymer Tantalum Capacitor, 10mΩ ESR (GSM Burst Buffer)
14	C4	1	100uF 10V X5R	Murata / TDK	`GRM31CR61A107ME15L`	1206 (3216 Metric)	High-Capacitance Ceramic MLCC, 10V, ±20%
15	L1	1	10uH 3.5A Shielded	Würth Elektronik	`744314101`	SMD WE-HCI 7030	High-Current Shielded Power Inductor (28mΩ DCR)
16	J1	1	MKDS 1,5/ 2-5,08	Phoenix Contact	`1715721`	Screw Terminal 2-Pin	2-Pos 5.08mm Pitch Industrial Terminal (Power In)
17	J2	1	MKDS 1,5/ 3-5,08	Phoenix Contact	`1715734`	Screw Terminal 3-Pin	3-Pos 5.08mm Pitch Industrial Terminal (RS-485 Port)
18	J4, J5	2	U.FL-R-SMT-1	Hirose Electric	`U.FL-R-SMT-1(10)`	U.FL SMT Vertical	Miniature 50Ω Coaxial RF Connectors (LTE & GNSS)
19	H1..H4	4	M3 Mounting Hole	Standard Hardware	`M3_Plated_3.2mm`	M3 Pad Via Shielded	Plated M3 Mechanical Mounting Holes (GND Connected)

📁 Repository Structure

text

InduLink-485/
├── docs/                               # Engineering documentation, CAD & schematics
│   ├── layers/                         # Individual high-resolution layer visualizations
│   │   ├── Layer1_Top_Copper.svg       # Layer 1 (F.Cu) + Silkscreen + Outlines
│   │   ├── Layer2_GND_Plane.svg        # Layer 2 (In1.Cu) Solid Ground Plane
│   │   ├── Layer3_Power_Plane.svg      # Layer 3 (In2.Cu) Power Distribution Rails
│   │   ├── Layer4_Bottom_Copper.svg    # Layer 4 (B.Cu) Bottom Signals + Silkscreen
│   │   └── All_Layers_Composite.svg    # 4-Layer full composite stackup view
│   ├── 3d/                             # 3D Mechanical CAD models
│   │   ├── InduLink-485.step           # Universal STEP 3D CAD Assembly
│   │   └── InduLink-485.glb            # Binary glTF 3D Web Visualization
│   ├── InduLink-485_Schematic.pdf      # Complete vector schematic PDF
│   ├── InduLink-485_PCB.pdf            # 4-Layer board fabrication drawing PDF
│   └── schematic/                      # Schematic sheet vector SVGs
├── fabrication/                        # Manufacturing & assembly packages
│   ├── gerbers/                        # RS-274X Gerber & Excellon Drill files
│   │   ├── InduLink-485-F_Cu.gtl       # Top Copper Layer
│   │   ├── InduLink-485-In1_Cu.g1      # Layer 2 Ground Plane
│   │   ├── InduLink-485-In2_Cu.g2      # Layer 3 Power Plane
│   │   ├── InduLink-485-B_Cu.gbl       # Bottom Copper Layer
│   │   ├── InduLink-485-F_Silkscreen.gto
│   │   ├── InduLink-485-F_Mask.gts
│   │   ├── InduLink-485-Edge_Cuts.gm1  # Board Outline & Milled Slots
│   │   └── InduLink-485-PTH.drl        # Plated Through-Hole Drill File

🚀 How to Build & Open the Project

Prerequisites

EDA Suite: KiCad 8.0+ (Compatible with KiCad 9 & 10).
Autorouter Engine (Optional): FreeRouting for running the Specctra DSN session.

Opening in KiCad

Clone the repository:

bash

git clone https://github.com/8aChristian/InduLink-485.git
cd InduLink-485

Open InduLink-485.kicad_pro inside KiCad.
Open the Schematic Editor or PCB Editor to view and edit the project.

📜 License & Author

Author: Christian Ochoa (@8aChristian)
License: Released under the MIT License.

Category and platform

ESP32

Project files

Show this board on your page

https://pcbkit.io/boards/8aChristian/InduLink-485

The board's own page, for a message or a post.

Source

Repository: 8aChristian/InduLink-485
Board file: InduLink-485.kicad_pcb
Commit: 55c74f9
Licence: MIT

Parts

Qty	Value	Footprint	References
4	M3_Hole	MountingHole_3.2mm_M3_Pad_Via	H1, H2, H3, H4
2	CD0402-T05C	D_0402_1005Metric	D4, D5
1	1000uF_6.3V_POSCAP	CP_EIA-7343-31_Kemet-D	C3
1	100uF_10V	C_1206_3216Metric	C4
1	10uH_3.5A	L_Wuerth_HCI-7030	L1
1	AP2112K-3.3TRG1	SOT-23-5	U4
1	B0505S-1WR3	Converter_DCDC_TRACO_TME_03xxS_05xxS_12xxS_Single_THT	U6
1	B240A	D_SMA	D2
1	ESP32-S3-WROOM-1-N8R8	ESP32-S3-WROOM-1	U1
1	GNSS_U.FL	U.FL_Hirose_U.FL-R-SMT-1_Vertical	J5
1	ISO7721DWR	SOIC-16W_7.5x10.3mm_P1.27mm	U5
1	LMR14030SDDAR	SOIC-8-1EP_3.9x4.9mm_P1.27mm_EP2.29x3mm	U3
1	LTE_U.FL	U.FL_Hirose_U.FL-R-SMT-1_Vertical	J4
1	MAX13487EESA+	SOIC-8_3.9x4.9mm_P1.27mm	U7
1	MF-MSMF075-2	Fuse_1812_4532Metric	F1
1	MKDS_1.5_2_5.08	TerminalBlock_Phoenix_MKDS-1,5-2-5.08_1x02_P5.08mm_Horizontal	J1
1	RS485_PORT	TerminalBlock_Phoenix_MKDS-1,5-3-5.08_1x03_P5.08mm_Horizontal	J2
1	SIM7080G	SIMCom_SIM7080G	U2
1	SM712.TCT	SOT-23	D3
1	SMCJ33CA	D_SMC	D1

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Questions

How big is the InduLink-485 PCB?

It measures 115 × 75 mm and has 4 copper layers, 1.6 mm thick.

What parts does the InduLink-485 use?

24 parts, built around the B0505S-1WR3, ESP32-S3-WROOM-1-N8R8, MAX13487EESA+ and SIM7080G. The full list of its parts is on this page, with links to each part's symbol and footprint where PCBKit's library has them.

Where can I download the InduLink-485 KiCad files?

From the 8aChristian/InduLink-485 repository on GitHub, at the commit this page was made from: the board is InduLink-485.kicad_pcb and its schematic InduLink-485.kicad_sch. PCBKit opens the board in the browser, with nothing to install.

Can I use the InduLink-485 design in my own project?

Its repository publishes it under the MIT licence: you may reuse it on that licence's terms (keep the author's notice, and for a copyleft licence share your changes alike).

Overview

Main components

B0505S-1WR3

ESP32-S3-WROOM-1-N8R8

MAX13487EESA+

SIM7080G

AP2112K-3.3TRG1

ISO7721DWR

100UF 10V

B240A

MF-MSMF075-2

SM712.TCT

SMCJ33CA