Assembly Guide

Before beginning the Protea assembly, prepare all necessary tools and materials for comfortable work. You will need:

  • Soldering station or temperature-controlled soldering iron (preferably with fine tip for SMD components)
  • High-quality solder with integrated flux (recommended diameter: 0.5–0.7 mm)
  • Liquid flux from reputable brands for SMD component soldering
  • Fine tweezers for handling small components
  • Magnifying glass or microscope for visual inspection of solder joints and troubleshooting shorts
  • Copper desoldering braid for removing excess solder
  • Isopropyl alcohol or other safe cleaning solution for flux residue removal, plus cotton swabs and/or toothbrush
  • Multimeter for circuit testing and voltage measurements

Workspace Requirements: Ensure your workspace is well-lit, ventilated, and has a heat-resistant surface. Use a PCB holder or “third hand” tool for convenience.

Assembly Sequence

The correct component installation order is crucial for successful Protea assembly.

Step 1: Power Supply Circuit

Install the power supply elements first: NCP1117-3.3 voltage regulator (U2), USB Type-C connector (J1), USBLC6-2SC6 protection IC (U3), and associated capacitors C2, C3 from the Power section. Connect pull-down resistors R2, R5 (5.1K each) for USB-C configuration. Verify the regulator’s 3.3V output using a multimeter when 5V power is applied to the USB-C connector.

Step 2: RP2040 Microcontroller Installation

Install the RP2040 microcontroller (U5)—the most challenging assembly stage. Use bottom board heating or preheat the installation area with hot air. Carefully center the microcontroller to align all 57 pins with the PCB pads. Install the 12MHz crystal oscillator (Y1) and associated 15pF capacitors (C17, C18) for the clock circuit.

Step 3: Flash Memory

Install the W25Q128JVSIQ flash memory IC (U4) which provides program storage for the RP2040.

Step 4: USB Multiplexer

Install the TS3USB221RSER USB multiplexer (U10) which switches USB connections between the RP2040 and CH340C USB-to-TTL converter.

Step 5: Signal Multiplexer

Install the SN74CBT3257CDR quad multiplexer (U1) for signal routing between different subsystems.

Step 6: Communication Modules

ESP8266 Module: Install the ESP-12F WiFi module (U8) with its associated pull-up resistors (R17, R18, R19, R20, R21 - all 10K) and decoupling capacitor C24. USB-to-TTL Converter: Install the CH340C IC (U9) with decoupling capacitors C26, C27.

Step 7: Interface Circuits

RS232 Interface: Install MAX232CSE+ (U6) with charge pump capacitors C19, C20, C21, C22 (all 1µF) and protection diodes D1, D2. USB-A Protection: Install USBLC6-2SC6 (U7) for USB-A port protection.

Step 8: Passive Components

Install all resistors and capacitors according to the BOM. Pay special attention to: decoupling capacitors (100nF) near each IC, pull-up/pull-down resistors for proper logic levels, HDMI termination resistors (270Ω) R22-R29

Step 9: User Interface Components

Install tactile switches: S1 (Boot button) for RP2040 programming mode, S2 (Reset button) for RP2040 reset, S3 (ESP Reset) for ESP8266 reset, S4 (Flash button) for ESP8266 programming mode. Install status LEDs: LD1 (Green) - Power indicator, LD2 (Blue) - RP2040 status, LD3, LD4 (Orange) - USB-to-TTL activity indicators

Step 10: Connectors

Install connectors in this order: J3 (USB-A connector), J2 (D-SUB 9 male for RS232), J5 (HDMI female connector), J4 (3-pin ESP8266 programming header), JP1 (6-pin main programming header), JP2 (ESP Reset header)

Component Classification

Essential components for basic operation:

  • Power section: U2 (NCP1117-3.3), U3 (USBLC6), J1 (USB-C), C2, C3, R2, R5, R4, R3, R6, LD1, R7
  • RP2040 core: U5 (RP2040), U4 (Flash), Y1 (Crystal), C17, C18, all decoupling capacitors
  • USB multiplexing: U10 (TS3USB221), U1 (SN74CBT3257), R32, R1, C28, C1
  • User interface: S1, S2 (Boot/Reset buttons), LD2

Optional Components:

  • Communication modules: ESP8266 section (U8 and associated components) can be omitted if WiFi functionality is not needed.
  • Interface connectors: RS232 (U6, J2) and USB-to-TTL (U9) sections are optional depending on intended use.

Testing Protocol

Test the board progressively during assembly:

  • Power Circuit: Verify 3.3V output at regulator after installing power section
  • RP2040 Core: After installing RP2040, flash memory, and crystal, verify the board enters bootloader mode when Boot button is pressed during power-up
  • USB Functionality: Test USB enumeration and communication
  • Optional Modules: Test each optional section (ESP8266, RS232, HDMI) individually after installation

Jumpers

There are two jumpers on the Protea board: J1 (switches) and J2 (solder jumper).

J1 switches are including the following functions:

U (USB Mode)

This switch selects the USB mode. When turned off, there is a direct connection between the USB-C port and the RP2040 microcontroller, allowing it to operate in programming mode. When turned on, the USB-C port is connected to the USB2TTL chip, allowing to program ESP8266 module.

D (Defaults)

Turn this switch before powering the Protea on to reset the board to factory defaults. This will clear all settings and configurations stored in the RP2040 module.

M (Mode)

When turned off, there is a connection between RP2040 and ESP8266 modules, allowing the RP2040 to communicate with the ESP8266 module. When turned on, the RP2040 module is connected to MAX232CSE chip, allowing you to connect to the external RS232 devices via DB9 port.

Solder jumpers:

J2

When soldered, there will be a connection between ESP_RESET of ESP8266 and GPIO16 of RP2040. This allows the RP2040 to reset the ESP8266 module when it is powered on. If you want to use the RP2040 module without the ESP8266, you can skip soldering this jumper. If you want to use the ESP8266 module, you need to solder this jumper.