1. Termination Resistors:
   • Place 120 ohm termination resistors at both ends of the RS485 bus to match the characteristic impedance of the cable.
   • Connect $R6:P1$ to $RS485_A:P1$ and $RS485_B:P1$.
2. Fail-Safe Biasing Resistors:
   • Add pull-up and pull-down resistors on the A and B lines to ensure a defined state when no driver is active.
   • Connect a pull-up resistor from $RS485_A:P1$ to VCC and a pull-down resistor from $RS485_B:P1$ to GND.
3. Common Mode Choke:
   • Adding a common mode choke on the A and B lines can help reduce common-mode noise.
4. TVS Diodes for Protection:
   • Install TVS diodes across the A and B lines to protect against voltage spikes.
   • Connect $D3:A1$ and $D3:A2$ to $RS485_A:P1$ and $RS485_B:P1$.
5. Isolators for Signal Integrity:
   • Use RS485 isolators to improve noise immunity and prevent ground loops.

• Main Components:
  • ESP32-WROOM-32E: A powerful microcontroller from Espressif Systems that provides Wi-Fi and Bluetooth capabilities.
  • MAX3485: A Maxim Integrated RS485/RS422 transceiver, facilitating communication over an RS485 network.
  • CH340C: A USB to serial converter chip, enabling USB connectivity for programming and communication with the ESP32.
  • AMS1117-3.3: A voltage regulator that provides a stable 3.3V output from a higher voltage input.
  • USB-C Connector (USB1): Used for power input and data transfer.
  • Diodes, Resistors, and Capacitors: Essential components used for protection, voltage regulation, filtering, and interfacing.
• Features & Functions:
  • The project incorporates RS485 communication via Modbus protocol, allowing the module to control or interact with a variety of devices that support this standard.
  • The inclusion of a USB-C port for power and programming flexibility.
  • Use of the CH340C chip for USB to serial conversion facilitates easy programming of the ESP32.
  • The AMS1117-3.3 voltage regulator ensures the ESP32 operates at a stable voltage.
  • The project also includes various GPIO (General Purpose Input/Output) pins and nets connected to various components and the ESP32 for interfacing and control purposes.
• Connectivity:
  • RS485 Communication: Managed by the MAX3485 transceiver, connected to the ESP32 for Modbus communication.
  • USB-C Interface: For programming the ESP32 and power supply.
• Miscellaneous:
  • The schematic contains nets, which are symbolic representations of connections between components. Each net in the schematic is associated with specific components and pins, indicating how they are electrically connected.
  • The design incorporates various protective elements like diodes (e.g., 1N5819HW-7-F for reverse voltage protection) and ESD protection components (e.g., SM712).
  • Several resistors and capacitors are used throughout the design for filtering, pull-up/pull-down functions, and ensuring signal integrity.
  • Power supply management is highlighted with dedicated nets and components for 3.3V and 5V supply lines.

1. Choose LED designators and resistors:
   • For simplicity, let's use the designators LED1 and LED2 for the LEDs.
   • Use resistors R10 and R11 to limit the current through the LEDs. Assume typical values like 330Ω.
2. Connect the LEDs to GPIO pins:
   • We'll assume you want to control the LEDs using two available GPIO pins from the ESP32-WROOM-32E.

• LEDs: Choose any standard LED with a forward voltage around 2V.
• Resistors: Use 330Ω resistors to limit the current to around 10mA.

1. For LED1:
   • Connect the anode (A) of LED1 to GPIO32.
   • Connect the cathode (K) of LED1 to one end of R10.
   • Connect the other end of R10 to GND.
2. For LED2:
   • Connect the anode (A) of LED2 to GPIO33.
   • Connect the cathode (K) of LED2 to one end of R11.
   • Connect the other end of R11 to GND.

• LED1:
  • Connect LED1:A to U2:IO32.
  • Connect LED1:K to R10:P1.
  • Connect R10:P2 to GND.
• LED2:
  • Connect LED2:A to U2:IO33.
  • Connect LED2:K to R11:P1.
  • Connect R11:P2 to GND.

• Connect LED1:A to U2:IO32.
• Connect LED1:K to R10:P1.
• Connect R10:P2 to GND.
• Connect LED2:A to U2:IO33.
• Connect LED2:K to R11:P1.
• Connect R11:P2 to GND.

1. Alimentación:
   • MAX485: VCC pin a 3.3V del ESP32.
   • MAX485: GND pin a GND del ESP32.
2. Comunicación:
   • MAX485: RO (Receiver Out) pin al pin RX de ESP32 $U2:RXD0/IO3$.
   • MAX485: DI (Driver In) pin al pin TX de ESP32 $U2:TXD0/IO1$.
   • MAX485: ~RE (Receiver Enable) pin al pin que desees configurar para control RE del ESP32 $\text{por ejemplo, } U2:IO4$.
   • MAX485: DE (Driver Enable) pin al mismo pin que ~RE para controlar ambos con el mismo pin del ESP32.
3. Bus RS485:
   • MAX485: A y B a las líneas diferenciales del bus RS485.

• Alimentación:
  • Conectar IC3:VCC a U2:VDD (3.3V)
  • Conectar IC3:GND a U2:GND
• Comunicación:
  • Conectar IC3:RO a U2:RXD0/IO3
  • Conectar IC3:DI a U2:TXD0/IO1
  • Conectar IC3:~RE a U2:IO4
  • Conectar IC3:DE a U2:IO4
• Bus RS485:
  • Conectar IC3:A a la línea A del bus RS485
  • Conectar IC3:B a la línea B del bus RS485

• Conectar IC3:VCC a U2:VDD
• Conectar IC3:GND a U2:GND
• Conectar IC3:RO a U2:RXD0/IO3
• Conectar IC3:DI a U2:TXD0/IO1
• Conectar IC3:~RE a U2:IO4
• Conectar IC3:DE a U2:IO4
• Conectar IC3:A a la línea A del bus RS485
• Conectar IC3:B a la línea B del bus RS485

1. ESP32-WROOM-32E
2. MAX3485CSA+
3. AMS1117-3.3
4. CH340C

• ESP32-WROOM-32E: Has multiple decoupling capacitors, but the voltage rating for each is not provided.
• MAX3485CSA+: Has one decoupling capacitor with no stated voltage rating.
• AMS1117-3.3: No decoupling capacitors are specified. According to the datasheet, this IC requires an output capacitor[1] which is not included.
• CH340C: Has two decoupling capacitors, but the voltage rating for each is not provided.

• Impedance Matching: RS485 networks generally use twisted pair cables, and the characteristic impedance of these cables is usually around 120 ohms. By adding a termination resistor (typically 120 ohms) at the ends of the communication line, the impedance is matched, preventing reflections.
• Signal Integrity: By minimizing reflections, the quality of the signal is maintained, ensuring reliable communication over long distances.

• Ends of the Bus: Termination resistors should be placed at both ends of the RS485 bus. This placement helps to absorb the signal energy and prevents it from reflecting back into the line.

• Designator: TERM
• Terminating Points: Connect the termination resistor across the differential lines, typically labeled as A and B.

1. For a 120-ohm termination
   • Connect TERM:P1 to RS485_A:P1 and TERM:P2 to RS485_A:P1

• Connect TERM:P1 to RS485_A:P1.
• Connect TERM:P2 to RS485_B:P1.

## Designator: TERM
Pins: 1 (name: P1),2 (name: P2)
Element Properties:
Exclude from BOM: true
Designator Prefix: SJ

• Function: Reduce signal reflection by impedance matching.
• Placement: At the ends of the RS485 communication line.
• Implementation: Use a 120-ohm resistor across A and B lines.

1. First Project: The best way to get started with Flux is to dive into creating your first project. This will help you familiarize yourself with the Flux interface and its basic functionalities. You can access a guide for starting your first project in the documentation or tutorials[1].
2. Tutorials: Flux offers detailed tutorials that cover everything from the basics to more advanced features. These tutorials are designed to help you understand how to design electronic schematics and lay out PCBs efficiently[1].
3. Reference Materials: For detailed information about specific elements of Flux, such as component placement, wiring, and layer management, refer to the reference section in the documentation. This is a great resource for finding in-depth information about Flux's capabilities[1].
4. YouTube: Explore Flux's library of video tutorials, crash courses, and recorded events on their YouTube channel. These videos can provide visual guidance on how to use Flux and often cover common use cases and complex projects[2].
5. Slack Community: Join the Flux Slack community to connect with other engineers, designers, and hardware enthusiasts. This platform allows you to ask questions, share your projects, and get direct support from the Flux team[3].
6. Live Support: If you need direct assistance or have specific questions, Flux's live support is available. Go to the contact section on their homepage to find how to get in touch[2].

1. ESP32-WROOM-32E: Este es el microcontrolador principal que maneja toda la lógica y control del proyecto. Tiene capacidades de Wi-Fi y Bluetooth, lo que lo hace versátil para aplicaciones de IoT.
2. MAX3485: Este es un transceptor RS485, que permite la comunicación serial en largas distancias y con alta inmunidad al ruido. Es esencial para la comunicación Modbus en tu proyecto.
3. USB-C Port: Proporciona alimentación y también permite la programación y depuración del ESP32 a través de una conexión USB.
4. Voltage Regulator (AMS1117-3.3): Regula la tensión de entrada (5V del puerto USB) a 3.3V, que es lo que requiere el ESP32 para funcionar correctamente.
5. CH340C: Este chip convierte señales USB a serial TTL. Permite la programación del ESP32 a través del puerto USB.

• Alimentación y Regulación:
  • Conecta USB1:VBUS a U1:VIN.
  • Conecta U1:VOUT a +3V3:P1.
  • Conecta U1:GND a GND:P1.
• ESP32 a RS485:
  • Conecta U2:TXD0/IO1 a IC3:DI.
  • Conecta U2:RXD0/IO3 a IC3:RO.
  • Conecta U2:IO4 a IC3:DE y IC3:~RE (control de transmisión).
• Interfaz USB a Serial:
  • Conecta USB1:DP1 a IC1:UD+.
  • Conecta USB1:DN1 a IC1:UD-.
  • Conecta IC1:TXD a U2:RXD0/IO3.
  • Conecta IC1:RXD a U2:TXD0/IO1.

• Primary Controller: Acts as the brain of the project with WiFi capabilities. It handles processing, execution of the logic, and communication with connected Modbus devices through the RS485 interface.
• Pins and Functions: It's connected to various GPIOs, power supply nets, and communication interfaces like RX/TX for serial communication.

• RS485 Communication: Responsible for translating data from the ESP32's TTL logic level to the RS485 differential signal, enabling robust long-distance communication characteristic of RS485.

• Power and Data: The USB-C port not only supplies power to the module but also serves as a data connection point, probably for programming the ESP32 and potentially for data transfer purposes.

• Voltage Regulator: Ensures a stable 3.3V power supply from a higher voltage source (likely from the USB-C connection) for powering the ESP32 and other 3.3V components.

• USB to Serial Converter: Facilitates the communication between a computer and the ESP32 module for programming or serial debugging.

• Dual Voltage Rails: Utilizes +3V3 and +5V power nets to accommodate different component requirements. The +3V3 line powers the logic and ICs, while the +5V might be used for USB power and any components requiring higher voltages.

• Capacitors (C1, C2, C3...): Used across the project for decoupling and noise filtering purposes.
• Resistors (R1, R2, R3...): Serve various purposes including pull-up/pull-down resistors for signal integrity, and biasing for the MAX3485.
• Interface Ports: Contains a USB Type-C port for power and data, and an RS485 port (marked as "A RS485 B") for Modbus communication.

• All the components and the design itself seem to adhere to the Creative Commons Attribution 4.0 International License, promoting openness and sharing in the hardware design community.

Diagram

• ESP32-WROOM-32E: Is the central processing unit. It interfaces with all other components.
• TYPE-C-31-M-12 (USB-C): Provides power and data connection.
• AMS1117-3.3: The voltage regulator ensures a stable 3.3V supply to the ESP32.
• MAX3485CSA+: Handles RS485 communication.
• CH340C: Responsible for USB to Serial conversion.
• SM712: TVS Diode for protection.
• GPIO (General Purpose IO): Represents various GPIOs available on the ESP32 used for various purposes.
• Sensor Interfaces: Highlight connections used for sensors.
• Power Supply Nets (3.3V, 5V, GND): Indicates the power supply connections.
• Peripherals: Show connection points for peripherals like RS485 and UART0.

• Designador: D2
• Nombre del Fabricante: Würth Elektronik
• Licencia: CC BY 4.0
• Pines:
  • Pin 1: IO1
  • Pin 2: GND
  • Pin 3: IO2
  • Pin 4: IO2
  • Pin 5: VDD
  • Pin 6: IO1

• Este componente está excluido de la lista de materiales (BOM) y de PCB, lo que sugiere que es probable que está siendo utilizado como un punto de unión o conexión intermedia en el circuito.
• Podría actuar como un puente de señales o un punto de prueba para facilitar la depuración o verificación de la señal.

• En un diseño como un módulo controlador con ESP32 y MAX3485 para comunicación Modbus, es posible que $D2$ esté sirviendo para conectar diferentes pistas de señal entre sí o incluso para cambiar el estado de una señal.

• Connect the anode of the RX LED to Net 12 (ESP RX).
• Connect the cathode of the RX LED through a current-limiting resistor (usually 220 ohms or 330 ohms) to GND.

• Connect the anode of the TX LED to Net 11 (ESP TX).
• Connect the cathode of the TX LED through a current-limiting resistor to GND.

• Connect the anode of the Enable LED to Net 6 (ESP EN).
• Connect the cathode of the Enable LED through a current-limiting resistor to GND.

• Make sure to choose the appropriate LED forward current and resistor value. A common choice for typical 3mm or 5mm LEDs is a resistor value of around 220 ohms to 330 ohms for 3.3V operation.
• Ensure the LEDs are oriented correctly, with the anode connected to the signal and the cathode to the GND.

• ESP32-WROOM-32E: This is a microcontroller module developed by Espressif Systems. It's the core of the project providing processing power, WiFi, and RF capabilities.
• MAX3485: This is an RS485 transceiver that allows the ESP32 to communicate with RS485 devices using the Modbus protocol. RS485 is a standard for serial data communication used in industrial environments.
• CH340C: A USB to serial converter that allows the device to interface with a USB port, typically for programming and communication with a computer.
• AMS1117-3.3: A voltage regulator that ensures a stable 3.3V supply to the ESP32 and other components.

• USB-C Port: Used for power and data, it connects the controller module to a computer or power source.
• RS485 Communication: Managed by the MAX3485 chip, it provides robust long-distance communication suitable for industrial environments.
• Passive Components: Various resistors and capacitors (e.g., $R1$, $C4$) are used for biasing, filtering, and stabilization of signals and power.

• Status LEDs and Buttons: Provides user interface and feedback for operations. The LEDs and switches like $BOOT$ and $RST$ are included for reset and boot functionalities.

• The ESP32's GPIO pins are used for controlling the RS485 transceiver and other peripheral components.
• The USB-C port powers the board and connects to the CH340C for USB communication.
• The MAX3485 is connected to the appropriate GPIO pins for RS485 data transmission.

• Signals are distributed throughout the board via network connections. For example, the 3.3V power net connects the voltage regulator output to various components such as the ESP32 and the CH340C.

• This module can be used in applications where remote monitoring or control is needed, leveraging Modbus communication over RS485. It is commonly used in industrial and automation systems.