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[Youtube] How to make BK7231 development board - NodeMCU conversion - soldering guide, hot air, SMD

p.kaczmarek2 7530 37

TL;DR LABEL_AI_GENERATED

  • A cheap NodeMCU ESP8266 board is converted into a BK7231 development board by transplanting a CB3S or WB3S Wi‑Fi module.
  • The process desolders the ESP12 with a hot air station, then solders the BK7231 module in its place using flux, leaded solder, solder wick, and PCB cleaner.
  • CB3S and WB3S are both covered, and CB3S has a slightly different pinout than WB3S.
  • The guide includes basic soldering tips, new pin mappings, and a working development-board demonstration.
AI summary based on the discussion. May contain errors.
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  • #31 21361708
    p.kaczmarek2
    Moderator Smart Home  
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    Here are mine:
    Various prototype boards and electronic modules on a wooden surface. A hand holding an electronic device with an LCD display module.
    I am thinking about using them with Wemos D1 converted to BK7231
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  • #32 21361714
    divadiow
    Level 38  
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    ah i see. shields are hats, extensions, add-ons. of course :)
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  • #33 21362685
    p.kaczmarek2
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    Those markings are so misleading:
    Two NodeMCU modules with pin labels visible on a dark background.
    I wonder how hard would it be to make a custom build (or a skin, or a script?) of OBK that will have NodeMCU-style pin names next to classic pin names...
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  • #34 21362718
    divadiow
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    interesting idea. Almost daily I'm referring to some mapping image on here or one I've made for various modules/ESP adaptors. Even some kind of basic ASCII selection to map choice1<->choice2. dunno

  • Interactive pin map draft with hover highlighting and handles

    #35 21362780
    p.kaczmarek2
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    Ok, so here is initial draft:
    https://openbekeniot.github.io/webapp/test1.html
    Open link and hover mouse cursor over pin name to higlight it.
    That's how it looks like:
    NodeMCU board diagram with highlighted GPIO pins.
    Next step would be to integrate it into pins chooser and GPIO doctor, I guess?
    Who knows html and js? @max4elektroda ? But maybe I will try to do it first myself. Keep the canvas and stuff as separate JS module on web app. Fetch it from web on pins page load. Allow user to select his board type, so NodeMCU, raw CB3S, etc, etc.

    Added after 3 [hours] 14 [minutes]:

    I added drawing handles:
    NodeMCU board pin diagram with highlighted pins.

    Added after 49 [minutes]:

    something like this, maybe?


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  • #36 21363276
    max4elektroda
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    That's really a very useful feature to easily identify the pins. Thanks!
    p.kaczmarek2 wrote:
    Who knows html and js? @max4elektroda ? But maybe I will try to do it first myself.

    You don't even allow some time to read before you present a nice realization ;-)

  • Need for a custom boards.json and storage plan

    #37 21363284
    p.kaczmarek2
    Moderator Smart Home  
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    I think I may get initial version working soon, but we will need to create our own "boards.json":
    ESP32 board pin diagram with a dropdown list for board selection.
    And there is also question where would we store board information, but since it's not a critical piece of information, I may just decid to store it in Cookie so it's a developer only feature remembered by current browser? Idk.... or add a command for that
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  • #38 21364328
    p.kaczmarek2
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    Recently I've did a very simple classic CB2S to NiceMCU transplant: CB2S/WB2S cheap dev board made from NiceMCU_WB3S_V1 (replace WB3S with WB2S/etc) . It might be good idea for anyone looking for cheap CB2S/WB2S dev boards, as NiceMCU is very cheap (as low as 1$ for new clients) and with my approach, the pin indexes on silkscreen are not mixed after conversion.
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Topic summary

LABEL_AI_GENERATED
The discussion centers on converting a cheap NodeMCU ESP8266 development board into a BK7231 development board by transplanting a BK7231 WiFi module (CB3S or WB3S) onto the NodeMCU PCB after desoldering the original ESP12 module using a hot air station. This method offers a cost-effective and flexible alternative to buying dedicated BK7231 dev boards, especially for users who have BK7231 modules salvaged from IoT devices. Key tools include a hot air station and basic soldering equipment, with some users exploring alternative heating methods like dual soldering irons due to lack of a heat gun. The transplant process involves careful desoldering, pad cleanup, and pin mapping verification, with some discussion on correcting pinout diagrams for I2C lines (S3, SK, SC) to ensure sensor compatibility (e.g., BMP280, AHT20). UART logging configuration is also addressed, recommending UART1 for logging due to CH340 USB interface connection. Additional topics include testing of TM1638 displays, power cycling via CEN or reset buttons, and the use of ShiftRegister for driving more LEDs. The community also explores software tools for pin mapping visualization and integration with OpenBK firmware. Alternative inexpensive boards without pre-soldered ESP modules are noted as options to avoid destructive desoldering. The conversation extends to related modules and development boards such as BK7238 NiceMCU, WEMOS W1F1 D1, and various BK series modules (CB2S, WB2S, CB3L, etc.), with interest in Arduino shield compatibility and custom firmware adaptations.
AI summary based on the discussion. May contain errors.
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FAQ LABEL_AI_GENERATED

TL;DR: In 3 main steps, a cheap NodeMCU ESP8266 can become a BK7231 dev board; the expert warning is "no need to desolder with hot air" if you choose a blank ESP-12 adapter instead. This FAQ helps OpenBeken users build, wire, flash, and debug CB3S/WB3S boards. [#20550797] Why it matters: This conversion gives BK7231 tinkerers a USB-TTL-equipped development board while reusing common ESP8266 hardware.

Option Best use Main advantage Main drawback
NodeMCU ESP8266 transplant Reusing a spare NodeMCU CH340 USB-TTL, reset button, 3.3 V rail Requires ESP-12 removal
Blank ESP-12 adapter board New BK7231 dev build No ESP desoldering needed Some bottom pads may not route anywhere
Universal ESP module board Testing many module footprints Supports CB3S, WB3S, ESP-12, ESP32-C3, HLK-B30 and more CEN/reset handling may need extra attention

Key insight: The transplant works, but pin mapping matters more than the soldering once the module boots. Always verify continuity before trusting a diagram, especially around S3, SC, SK, P20, P21, and P23.

Quick Facts

  • Required parts are a CB3S or WB3S module, a NodeMCU board, hot air, flux, Pb solder, solder wick, PCB cleaner, and a soldering iron. [#20549683]
  • OpenBeken build 1.17.53 can move logging to UART1 using SetFlag 31 1 and logPort 1. [#20555441]
  • UART1 on this converted board uses RXD1/TXD1, programming pins, CH340 USB-TTL, and a default speed of 115200 baud. [#20555516]
  • Confirmed CB3S mappings include S3 → P21, SC → P23, and SK → P20 after continuity checks. [#21065051]
  • A universal ESP adapter was reported to support over 25 module names, including BT3L, CB3S, WB3S, ESP-12, HLK-B30, and ESP32-C3. [#21048408]

How do you convert a cheap NodeMCU ESP8266 board into a BK7231 development board using a CB3S or WB3S module?

Remove the ESP-12 module and solder a CB3S or WB3S module in its place.
  1. Heat and desolder the ESP-12 from the NodeMCU.
  2. Clean pads with flux, Pb solder, wick, and PCB cleaner.
  3. Align the CB3S or WB3S, tack one corner, then solder all pads.
The original guide shows both CB3S and WB3S versions, plus a working board after conversion. [#20549683]

What tools and soldering supplies are needed to transplant a BK7231 CB3S or WB3S module onto a NodeMCU board?

You need a CB3S or WB3S module, NodeMCU board, hot air station, soldering iron, flux, Pb solder, solder wick, and PCB cleaner. The thread says even the cheapest hot air station is enough for the job. The module can come from a Tuya-style IoT device, while the removed ESP can go back into that donor device. [#20549683]

What is the difference between CB3S and WB3S pinouts when converting a NodeMCU board to BK7231?

CB3S and WB3S use slightly different pinouts, so you must use the correct mapping image before soldering. The first post explicitly warns that CB3S has a different pinout than WB3S. Later continuity checks corrected specific CB3S NodeMCU labels, including S3, SC, SK, P20, P21, and P23. [#20549683]

NodeMCU conversion vs blank ESP-12 adapter board: which is better for making a BK7231 dev board?

Use NodeMCU when you want built-in CH340 USB-TTL and reset hardware; use a blank ESP-12 adapter when you want less desoldering. One participant noted that inexpensive boards exist with everything except the ESP module. The original author agreed their key benefit is "no need to desolder with hot air" from a NodeMCU. [#20550797]

How can you remove an ESP-12 module from a NodeMCU board without a hot air station?

You can remove it with soldering irons and extra Pb solder, but the thread treats this as a harder workaround. One successful method heated the short bottom edge with an old iron, then used long Pb solder across the other two sides. The failure risk is real: the module shot across the desk, and a 3.3 V trace was damaged during cleanup. [#21020097]

What soldering station or hot air station works well for desoldering ESP-12, CB3S, or WB3S modules?

A basic hot air station works; the guide says the cheapest one is enough. A later comment calls a heat gun a must-have for clean ESP-12 removal from NodeMCU. Without hot air, high-power soldering iron tricks may work, but they need enough heat capacity for three soldered module edges. [#21012728]

How do you fix a damaged 3.3V pad or trace after removing the ESP8266 module from a NodeMCU board?

Bridge the damaged 3.3 V path with a bodge wire after confirming lost continuity. One build lost continuity between the AMS1117 regulator and the module after pad cleanup. The board did not power the CB3S until a direct repair wire restored the 3.3 V connection. Always check continuity before final soldering. [#21020097]

How do you configure OpenBeken to use UART1 for logging on a converted BK7231 NodeMCU board?

Enable the UART command line and set UART1 as the log port. Use this OpenBeken script: SetFlag 31 1 logPort 1 This works from build 1.17.53. The thread notes UART1 uses RXD1/TXD1, which are also used for programming and TuyaMCU or BL0942 connections. [#20555441]

What is UART, and why does switching the OpenBeken log port from UART2 to UART1 help on a NodeMCU-based BK7231 board?

UART1 helps because the NodeMCU board already connects it to the CH340 USB-TTL chip. "UART is a serial communication interface that sends and receives data over TX and RX pins, commonly used for logs, command lines, firmware flashing, and module-to-host debugging at fixed baud rates." The default UART2 would need a separate USB-to-UART converter just for logs. [#20555512]

What is CEN on BK7231 modules, and how can it be used for reset or power-cycle behavior on ESP adapter boards?

CEN is the reset-enable control line used to restart BK modules on adapter boards. "CEN is a BK module control pin that resets or enables the chip, letting a button or ground connection restart the module without fully unplugging the USB-powered adapter." One adapter had a reset button, and another user considered adding a push button to ground CEN. [#21075406]

What is a ShiftRegister in OpenBeken, and how can it help drive more LEDs from a BK7231 board?

ShiftRegister lets OpenBeken drive more LEDs than the directly available GPIO pins. "ShiftRegister is an OpenBeken driver feature that expands digital outputs through an external serial register, allowing one BK7231 board to control multiple LEDs using fewer native GPIO pins." It was suggested after testing normal GPIO-driven LEDs on the converted board. [#21025386]

What are the correct CB3S-to-NodeMCU pin mappings for S3, SC, SK, P20, P21, and P23 after the transplant?

The verified mapping is S3 → P21, SC → P23, and SK → P20. This corrected an earlier diagram error. The mistake affected I2C testing because the user expected P20 to map to S3, but continuity showed P20 went to SK. P21 went to S3 instead. [#21065051]

Why might an I2C BMP280 or AHT20 sensor be detected but not work correctly on a converted BK7231 NodeMCU board?

Wrong pin mapping can make I2C appear partly alive while the sensor still fails. The thread found an I2C device at address 0x77, but later discovered the NodeMCU diagram mixed S3 and SK-related mappings. The affected test involved BMP280/AHT20 modules and OpenBeken I2C pins. [#21065038]

What are Arduino shields, and why would converting a WEMOS W1F1 D1 ESP8266 board to BK7231 be useful for testing them?

Arduino shields are plug-in add-on boards for the Arduino-style header layout. "Arduino shields are expansion boards that stack onto compatible development boards, adding hardware such as displays, relays, sensors, or interfaces through predefined header positions." A converted WEMOS W1F1 D1 could let BK7231 firmware test those shield-style peripherals. [#21361714]

How could OpenBeken display NodeMCU-style pin names alongside classic BK7231 GPIO names to avoid wiring mistakes?

OpenBeken could load a board map and show NodeMCU labels beside BK GPIO names in the pins UI. The thread proposed a boards.json approach, mouse-hover highlighting, and integration with the pins chooser and GPIO doctor. The goal was to reduce daily lookup errors between NodeMCU labels and classic BK7231 names. [#21362780]
AI summary based on the discussion. May contain errors.
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