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Qiachip Smart Switch - BK7231N / CB2S - interior, programming

p.kaczmarek2 77310 310

TL;DR

  • Qiachip Smart Switch contains a CB2S Wi‑Fi/Bluetooth module based on the BK7231N, not the BK7231T, inside a simple relay board with BP2525 supply and AMS1117 regulator.
  • OpenBK7231N required porting SDK files, fixing Cygwin toolchain use, correcting file names, and resolving a partition conflict caused by RL_SUPPORT_FAST_CONNECT.
  • BKwriter 1.60 failed with CRC verification and unprotect bugs, so flashing used Tuya's hid_download_py with --unprotect, --startaddr 0x0, and a reset on CEN.
  • The QIO firmware uploaded successfully, the configuration AP appeared, and the device can then be managed through 192.168.4.1, MQTT, and Home Assistant.
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  • #151 20181014
    kajarit
    Level 6  
    Posts: 14
    Hello All,

    I have a temperature and humidity sensor with a CB3S module, which I'm trying to free from tuya cloud with your very promising BK7231N firmware. It works with 2 AA batteries. The article number is TW-TH002 I think.

    Qiachip Smart Switch - BK7231N / CB2S - interior, programming
    Qiachip Smart Switch - BK7231N / CB2S - interior, programming

    I have a CH340G USB to TTL deivce for the task.
    Qiachip Smart Switch - BK7231N / CB2S - interior, programming

    I connected pins to the CB3S (8) VCC, (9) GND, (15) RX, (16) TX, and for resetting (3) CEN, and could download the firmware, but with CRC errors. TTL device is set to 3.3V.
    When I try to write the BK7231N (OpenBK7231N_QIO_1.12.48.bin) with -s 0x0, -u options, then I get an error right after start: "WriteSector 1 Failed"
    Do you have any idea how to continue?
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  • #152 20181144
    p.kaczmarek2
    Moderator Smart Home  
    Posts: 14388
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    What is the marking on the chip in SOIC?

    I'd guess that's a TuyaMCU device. Most likely TuyaMCU has to be temporarily removed because it shared TX and RX lines with the lines that are used for programming.

    Second option would be to send 2MB flash dump to tuya-cloudcutter guys and wait for them to prepare OTA support for this device.

    Can you check with multimeter where the RX and TX of CB3S goes to? Is it connected to the MCU? Just to confirm...
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  • #153 20181477
    kajarit
    Level 6  
    Posts: 14
    Could you clarify, I don't understand this:
    Quote:
    What is the marking on the chip in SOIC?


    Okay, I'll check next week as soon as I can, and get back to you.

    I could see a very similar device that you successfully flashed in post #100, did you cut the RX/TX connection to the MCU there?
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  • #154 20181586
    p.kaczmarek2
    Moderator Smart Home  
    Posts: 14388
    Help: 650
    Rate: 12308
    kajarit wrote:
    Could you clarify, I don't understand this:
    Quote:
    What is the marking on the chip in SOIC?


    I am asking what is the chip name from the photo, because It's a bit blurry and it's hard for me to read.

    kajarit wrote:

    I could see a very similar device that you successfully flashed in post #100, did you cut the RX/TX connection to the MCU there?

    I had to cut RX/TX in order to flash, but it might be not necessary if you identify the chip and find if it has a reset pin in its datasheet.
    Here is more information about that device, sadly only in polish so far (use google translate):
    https://www.elektroda.pl/rtvforum/topic3914412.html
    Helpful post? Buy me a coffee.
  • #155 20185445
    gowthaml
    Level 7  
    Posts: 12
    Hello All,
    I have smart switch with CB3S chip module, I am tried to establish connection with MQTT which I was hosted in remote server with Public IP and successfully connection establish with MQTT server while try to publish data to the device its started reboot without any error code's, I am tried multiple times publish data to device but its successfully subscribed to the server but starts reboot while receiving data..!!

    V:BK7231N_1.0.1
    REG:cpsr spsr r13 r14
    SVC:0000001F 00414570 0004C9F9
    IRQ:000000d2 0000003f 004037f0 000926e4
    FIR:000000d1 6000001f 00402800 00057bc8
    SYS:000000df 00414570 0004c9f9
    ST:00000000
    J 0x10000
    bk_misc_init_start_type a 0
    prvHeapInit-start addr:0x40dd90, size:139888
    [Flash]id:0x1c7015
    sctrl_sta_ps_init
    xat0_reboot


    V:BK7231N_1.0.1
    REG:cpsr spsr r13 r14
    SVC:000000D3 00401C1C 000033AC
    IRQ:000000d2 00000010 00401e0c 00005320
    FIR:000000d1 00000010 00401ffc 00057bc8
    SYS:000000df 0040192c 00000158
    ST:0001AD05
    J 0x10000
    bk_misc_init_start_type 5 1ad05
    prvHeapInit-start addr:0x40dd90, size:139888
    [Flash]id:0x1c7015
    sctrl_sta_ps_init
    cset:0 0 0 0
    bandgap_calm_in_efuse=0x62
    [load]bandgap_calm=0x62->0x22,vddig=4->5
    [FUNC]rwnxl_init
    [bk]tx_txdesc_flush
    [FUNC]intc_init
    [FUNC]calibration_main
    gpio_level=1,txpwr_state=15
    user define rfcali mode:1
    get rfcali_mode:1

    calibration_main over
    flash txpwr table:0xf
    dif g and n20 ID in flash:4
    dif g and n40 ID in flash:4
    read txpwr tab from flash success
    temp in flash is:358
    xtal in flash is:66
    xtal_cali:66
    --init_xtal = 66
    [FUNC]ps_init
    [FUNC]func_init_extended OVER!!!

    start_type:5
    Version:
    Initializing TCP/IP stack
    tcp_port:62642
    app_init finished

    Periodic reboot t[sa_sta]MM_RESET_REQ
    [bk]tx_txdesc_flush
    a
    [sa_sta]ME_CONFIG_REQ
    [sa_sta]ME_CHAN_CONFIG_REQ
    [sa_sta]MM_START_REQ
    ht in scan
    scan_start_req_handler
  • #156 20185456
    p.kaczmarek2
    Moderator Smart Home  
    Posts: 14388
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    Hello, have you tried fixed 2MB binary from this post?
    https://www.elektroda.com/rtvforum/topic3874289-90.html#20148034
    Helpful post? Buy me a coffee.
  • #157 20185480
    gowthaml
    Level 7  
    Posts: 12
    p.kaczmarek2 wrote:
    Hello, have you tried fixed 2MB binary from this post?
    https://www.elektroda.com/rtvforum/topic3874289-90.html#20148034


    No, I am just followed "https://www.elektroda.com/rtvforum/topic3874289.html" this post and tried to connect with MQTT and successfully connected with if data tried to received device reboots..!!!

    As you said from above reply if I removed garbages values by flashing 2MB firmware, you said to backup Mac address and how can i backup MAC address?
  • #158 20185760
    kajarit
    Level 6  
    Posts: 14
    p.kaczmarek2 wrote:
    kajarit wrote:
    Could you clarify, I don't understand this:
    Quote:
    What is the marking on the chip in SOIC?


    I am asking what is the chip name from the photo, because It's a bit blurry and it's hard for me to read.


    I couldn't make a better picture, but I think this is an Unicmicro UM8005-ACTE (TSSOP20) microcontroller.
  • #159 20185932
    p.kaczmarek2
    Moderator Smart Home  
    Posts: 14388
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    gowthaml wrote:

    As you said from above reply if I removed garbages values by flashing 2MB firmware, you said to backup Mac address and how can i backup MAC address?

    just change MAC to anything you want after doing the flashing, you can change MAC in obk settings

    kajarit wrote:
    p.kaczmarek2 wrote:
    kajarit wrote:
    Could you clarify, I don't understand this:
    Quote:
    What is the marking on the chip in SOIC?


    I am asking what is the chip name from the photo, because It's a bit blurry and it's hard for me to read.


    I couldn't make a better picture, but I think this is an Unicmicro UM8005-ACTE (TSSOP20) microcontroller.

    Qiachip Smart Switch - BK7231N / CB2S - interior, programming
    I didn't have time to read whole datasheet, but you can find one on the web, and it seems there is a RST pin. Maybe connecting this pin to ground or something will put chip in RESET mode and allow you to read and write flash from UART with no interference.
    Otherwise you will have to cut the tracks... the UART used to talk with this chip is the same as programming UART
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  • #160 20186114
    gowthaml
    Level 7  
    Posts: 12
    p.kaczmarek2 wrote:

    just change MAC to anything you want after doing the flashing, you can change MAC in obk settings



    As you said flashed full firmware bin file to remove garbage values from flash and after removing all again flashed firmware and start trying to connect with MQTT but this time MQTT while trying to subscribe topic its starts reboot..!!


    MQTT client "cbs" connection cb: status 0

    MQTT client "cbs" request cb: err 0
    MQTT client "cþ
    V:BK7231N_1.0.1
    REG:cpsr spsr r13 r14
    SVC:0000001F 00414570 0004C9F9
    IRQ:000000d2 0000003f 004037f0 0004c524
    FIR:000000d1 6000001f 00402800 00057bc8
    SYS:000000df 00414570 0004c9f9
    ST:00000000
    J 0x10000
    bk_misc_init_start_type a 0
    prvHeapInit-start addr:0x40dd90, size:139888
    [Flash]id:0x1c7015
    sctrl_sta_ps_init
    xat0_reboot

    [13:52:22.004]IN¡û¡ô
    V:BK7231N_1.0.1
    REG:cpsr spsr r13 r14
    SVC:000000D3 00401C1C 000033AC
    IRQ:000000d2 00000010 00401e0c 00005364
    FIR:000000d1 00000010 00401ffc 00057bc8
    SYS:000000df 0040192c 00000158
    ST:0001AD05
    J 0x10000
    bk_misc_init_start_type 5 1ad05
    prvHeapInit-start addr:0x40dd90, size:139888
    [Flash]id:0x1c7015
    sctrl_sta_ps_init
    cset:0 0 0 0
    bandgap_calm_in_efuse=0x62
    [load]bandgap_calm=0x62->0x22,vddig=4->5
    [FUNC]rwnxl_init
    [bk]tx_txdesc_flush
    [FUNC]intc_init
    [FUNC]calibration_main
    gpio_level=1,txpwr_state=0
    user define rfcali mode:1
    get rfcali_mode:1

    [13:52:22.488]IN¡û¡ôcalibration_main over
    NO TXPWR_TAB_TAB found in flash
    Load default txpwr for b:0x95844
    Load default txpwr for g:0x95852
    fit n20 table with dist:4
    Load default txpwr for n40:0x95860
    Load default txpwr for ble:0x966d9
    temp in flash is:350
    xtal in flash is:12
    xtal_cali:12
    --init_xtal = 12
    [FUNC]ps_init
    [FUNC]func_init_extended OVER!!!
  • #161 20186490
    p.kaczmarek2
    Moderator Smart Home  
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    Are you saying that it reboots even after @00svd00 fix?

    Ok, can you check the very same version that I have running for 18 days already?
    Qiachip Smart Switch - BK7231N / CB2S - interior, programming
    This version: Build on Aug 22 2022 23:03:50 version 1.12.41 pick that one from releases and check.
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  • #162 20186918
    gowthaml
    Level 7  
    Posts: 12
    Yes, as you said I reflashed 2MB firmware and tested still reboots on subscribing topic. If not subscribed its connecting to MQTT server and can able to publish data. I am just trying to implement own MQTT connection establishment from this below example post https://www.elektroda.com/rtvforum/topic3850712.html
    I am trying your example own MQTT connection from above post and not trying to use home assistance or Tasmota.
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  • #163 20187108
    p.kaczmarek2
    Moderator Smart Home  
    Posts: 14388
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    Wait wait wait, are you saying that you're not using OpenBeken?
    You are linking to the old non-OBK tutorial of mine...
    Can you confirm, are you using OpenBeken or are you trying to write your own code?
    Can you show me your code?
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  • #165 20187440
    p.kaczmarek2
    Moderator Smart Home  
    Posts: 14388
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    gowthaml wrote:
    Yes, I am using own code to connect with server and using your example reference code from below topic
    https://www.elektroda.com/rtvforum/topic3850712.html

    Oh c'mon, you really got me worried, everyone thought you're talking about OpenBeken.

    Ok, now, I know this issue. I and @btsimonh has most likely experienced the same.
    I don't remember the fix from the top of my head, but here are 3 hints:
    1. don't start WiFi just after rebooting device, wait a 5 or so seconds (it's already in obk)
    2. don't start MQTT immediately, start it when WiFi reports a successful connection, maybe with extra delay
    3. do not do MQTT calls within MQTT callbacks - or something like that...
    4. the best now you can do is to look back at the history of my OBK drafts, maybe attachment from first post:
    https://www.elektroda.com/rtvforum/topic3866123.html
    or maybe in obk history itself:
    https://github.com/openshwprojects/OpenBK7231...h=master&qualified_name=refs%2Fheads%2Fmaster
    https://github.com/openshwprojects/OpenBK7231...d38dc670/apps/my_alpha_demo/src/tuya_device.c
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  • #166 20187483
    gowthaml
    Level 7  
    Posts: 12
    Thank You so much sir, Its worked fine by adding some delay and mqtt callback in proper way solved the issues. :D
    Do you have any proper way of storing wifi cred into flash and read from flash ?
  • #167 20187542
    p.kaczmarek2
    Moderator Smart Home  
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    Here are my functions used to access flash memory on BK7231 platform:
    https://github.com/openshwprojects/OpenBK7231.../main/src/hal/bk7231/hal_flashConfig_bk7231.c
    Here is the abstract config that is shared between all platforms:
    https://github.com/openshwprojects/OpenBK7231T_App/blob/main/src/new_cfg.c
    Here is the Tuya method (or maybe Beken?) of saving data to flash (I used it in the past):
    https://github.com/openshwprojects/OpenBK7231..._os/beken378/func/user_driver/BkDriverFlash.c
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  • #168 20193469
    kajarit
    Level 6  
    Posts: 14
    p.kaczmarek2 wrote:
    I didn't have time to read whole datasheet, but you can find one on the web, and it seems there is a RST pin. Maybe connecting this pin to ground or something will put chip in RESET mode and allow you to read and write flash from UART with no interference.
    Otherwise you will have to cut the tracks... the UART used to talk with this chip is the same as programming UART


    I couldn't achieve better results by trying to connect GND to Unicmicro UM8005-ACTE (TSSOP20) microcontroller's RST - which I think is pin 4: P0.2/NRST.
    So I cut the tracks to RX, TX on the back, checked with multimeter, definitely not connected anymore.
    However I still get CRC check failed at the end of backup.
    Any idea?
  • #169 20193574
    p.kaczmarek2
    Moderator Smart Home  
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    CRC error is normal in case of this flashing tool and can be ignored. There is nothing to worry about.

    If all sectors were read, and you have a 2MB file, then it's ok already.

    When in doubt, just do a backup twice.
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  • #170 20193783
    kajarit
    Level 6  
    Posts: 14
    p.kaczmarek2 wrote:
    CRC error is normal in case of this flashing tool and can be ignored. There is nothing to worry about.

    If all sectors were read, and you have a 2MB file, then it's ok already.

    When in doubt, just do a backup twice.


    Okay, I thought this CRC check is working.

    Sure I think so, the file size is 2097152 bytes.

    Actually I made 4 files with the following settings, which one is the best? :)
    1. -l 0x200000 -b 115200
    2. -s 0x0 -l 0x200000 -b 115200
    3. -l 0x200000 -u -b 115200
    4. -s 0x0 -l 0x200000 -u -b 115200

    Added after 41 [minutes]:

    I tried to upload the firmware file OpenBK7231N_QIO_1.12.55.bin (options -s 0x0 -u), but after getting the bus, it stops with the below error:
    Code: Text
    Log in, to see the code


    Also if I didn't set -b 115200, then it stops with:
    Code: Text
    Log in, to see the code
  • #171 20200373
    p.kaczmarek2
    Moderator Smart Home  
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    This is the one I use and it's proven that it works (but -u is a shorthand for --unprotect):
    Code: text Expand Select all Copy to clipboard
    
python uartprogram LastBuild.bin --unprotect -d com10 -w --startaddr 0x0
pause


    kajarit wrote:


    I tried to upload the firmware file OpenBK7231N_QIO_1.12.55.bin (options -s 0x0 -u), but after getting the bus, it stops with the below error:
    Code: Text
    Log in, to see the code


    Also if I didn't set -b 115200, then it stops with:
    Code: Text
    Log in, to see the code


    Anyway, are we talking about the same device you have already programmed before?
    Regarding the problems, I need to have more information. There can be multiple reasons for such error. Can you show a photo of your setup?
    1. Was it working earlier? I am not sure as it sounded you are already flashing it correctly and now you report errors.... is it the same device?
    2. Do you have anything also connected on RX/TX lines? There are some devices that have, for example, a debouncing capacitor on RX line (I've had such relay once) that needs to be removed before flashing. Some other devices might use RX/TX lines to communicate with TuyaMCU chip, which also makes flashing a bit more problematic, because you have to remove TuyaMCU or cut the lines first (or put the MCU In reset state)
    3. How do you reset the WiFi module, by CEN or by power on/off cycle? Doing a reset is tricky, it takes several times to get it right.

    BTW: If you have successfully done a firmware backup, you can submit it here:
    https://github.com/tuya-cloudcutter/tuya-cloudcutter/issues

    EDIT: Or are you trying to say that flashing your own build worked, but flashing OBK does not?
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  • #172 20201872
    kajarit
    Level 6  
    Posts: 14
    p.kaczmarek2 wrote:


    Anyway, are we talking about the same device you have already programmed before?
    Regarding the problems, I need to have more information. There can be multiple reasons for such error. Can you show a photo of your setup?
    1. Was it working earlier? I am not sure as it sounded you are already flashing it correctly and now you report errors.... is it the same device?
    2. Do you have anything also connected on RX/TX lines? There are some devices that have, for example, a debouncing capacitor on RX line (I've had such relay once) that needs to be removed before flashing. Some other devices might use RX/TX lines to communicate with TuyaMCU chip, which also makes flashing a bit more problematic, because you have to remove TuyaMCU or cut the lines first (or put the MCU In reset state)
    3. How do you reset the WiFi module, by CEN or by power on/off cycle? Doing a reset is tricky, it takes several times to get it right.


    We're talking about the same thermometer (and humidity) device, which I try to flash with your bin, couldn't flash it yet.

    1. Nope, I wrote this in my first post:
    Quote:
    When I try to write the BK7231N (OpenBK7231N_QIO_1.12.48.bin) with -s 0x0, -u options, then I get an error right after start: "WriteSector 1 Failed"


    2. Only the MCU was, I've cut the lines as the MCU RST pin grounding didn't do the trick for me.
    Quote:
    I couldn't achieve better results by trying to connect GND to Unicmicro UM8005-ACTE (TSSOP20) microcontroller's RST - which I think is pin 4: P0.2/NRST.
    So I cut the tracks to RX, TX on the back, checked with multimeter, definitely not connected anymore.


    3. By connecting CEN to ground, as I mentioned before. This is working as it starts the backup process also (until I don't ground it, it waits).
    Quote:
    I connected pins to the CB3S (8) VCC, (9) GND, (15) RX, (16) TX, and for resetting (3) CEN
  • #173 20202226
    p.kaczmarek2
    Moderator Smart Home  
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    Ah ok @kajarit , I mistaken your post with @gowthaml

    So you were never able to flash any binary to this device yet, right? Not even reflash back the backup of the firmware? But you can READ correctly the flash?

    Is your power connect directly to CB3S? 3.3V to 3.3V of CB3S? I am asking because this board has a transistor and TuyaMCU by default turns off the WiFI module after some time.
    Or maybe is your 3.3V connected to the battery connector? If so, it's a wrong approach, because TuyaMCU can disconnect that.
    Qiachip Smart Switch - BK7231N / CB2S - interior, programming

    Other than that, I am running out of ideas. Take a look here:
    https://www.elektroda.pl/rtvforum/topic3914412.html
    it might not be yet translated (use Google Translate) but I have easily flashed both such boards as in linked topic by cutting RX/TX traces and powering the WiFi module directly (to the 3.3V pin of CB3S)


    Maybe your UART to USB converter has not enough current capability? Can you show photos? Have you tried powering it from external LDO 3.3V?
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  • #174 20202389
    kajarit
    Level 6  
    Posts: 14
    p.kaczmarek2 wrote:
    Is your power connect directly to CB3S? 3.3V to 3.3V of CB3S? I am asking because this board has a transistor and TuyaMCU by default turns off the WiFI module after some time.
    Or maybe is your 3.3V connected to the battery connector? If so, it's a wrong approach, because TuyaMCU can disconnect that.


    I've soldered wires directly to each pin on the CB3S, I'll provide photos later, when I get home.

    Added after 3 [minutes]:

    p.kaczmarek2 wrote:
    Maybe your UART to USB converter has not enough current capability? Can you show photos? Have you tried powering it from external LDO 3.3V?


    I'm using a "golden standard" :) USB to TTL dongle, as recommended "officially" for Tasmota. However I don't know how to check that for sure.

    Quote:
    Many CH340G devices will not work, the "golden CH340G" has a voltage regulator on it to supply enough power to the ESP device - many do not. The ESP requires at least 150mA, many 3.3V serial programmers do not supply this much current as many serial programming tasks do not require a large amount of power.
  • #175 20202405
    p.kaczmarek2
    Moderator Smart Home  
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    If you're using CEN for resetting, what about putting in the device two AAA batteries and then doing a temporary short around the power control MOSFET?
    This way you will power the CB3S from batteries and not from USB to UART converter. Also, of course, disconnect the USB to UART converter from VCC in this case.

    I have a slight feeling that I remember sometime ago having issue with writing but being able to read, and it was because of write operation requiring slightly more current, but maybe I am wrong.
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  • #176 20202909
    kajarit
    Level 6  
    Posts: 14
    p.kaczmarek2 wrote:
    Ah ok @kajarit , I mistaken your post with @gowthaml
    Maybe your UART to USB converter has not enough current capability? Can you show photos? Have you tried powering it from external LDO 3.3V?


    Powering it through the "golden" CH340G which is - in theory - able to provide 150mA according to specs.

    Qiachip Smart Switch - BK7231N / CB2S - interior, programming Qiachip Smart Switch - BK7231N / CB2S - interior, programming
  • #177 20224099
    gowthaml
    Level 7  
    Posts: 12
    Hello All,
    Have any one ported mdns application for cb2s from lwip? If yes , then how can I enable mdns and use mdns?
  • #178 20228436
    p.kaczmarek2
    Moderator Smart Home  
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    @gowthaml why do you need that? I might look into it.

    IMPORTANT UPDATE
    The N platform instability has been fixed (or at least seriously improved).
    The LWIP version has been updated.
    The N platform should not crash anymore, at least because of LWIP.

    This addresses the issues discussed earlier in this thread.
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  • #179 20228495
    gowthaml
    Level 7  
    Posts: 12
    I am using my own Wi-Fi credentials method and I need mDNS to resolve ip addresses of the device .
  • #180 20231037
    omelchuk890
    Level 11  
    Posts: 70
    Rate: 10
    I bought some more switches.
    I immediately got caught on the BK7231N ...
    The body of the product is like the previous ones, but those were on T.
    I'm thinking how to connect?
    Soldering everyone is stressful. I'll try to make a needle connector for the points on the board.
    Spoiler:
    Qiachip Smart Switch - BK7231N / CB2S - interior, programming20221011_0..303.jpg (510.14 kB)You must be logged in to download this attachment. Qiachip Smart Switch - BK7231N / CB2S - interior, programming20221011_0..925.jpg (606.35 kB)You must be logged in to download this attachment. Qiachip Smart Switch - BK7231N / CB2S - interior, programming20221011_0..102.jpg (336.92 kB)You must be logged in to download this attachment. Qiachip Smart Switch - BK7231N / CB2S - interior, programming20221011_0..111.jpg (368.41 kB)You must be logged in to download this attachment. Qiachip Smart Switch - BK7231N / CB2S - interior, programming20221011_0..058.jpg (336.79 kB)You must be logged in to download this attachment. Qiachip Smart Switch - BK7231N / CB2S - interior, programming20221011_1..743.jpg (274.26 kB)You must be logged in to download this attachment.


    After a while, at 18.16
    The board was stitched using soldering and the command line. the most recent at the moment OpenBK7231N_QIO_1.12.103.bin.
    It was an interesting shamanism, my hand hurts from the tambourine ...
    I will try, if the Author of the topic does not mind, tomorrow I will write a detailed, step-by-step, guide for the BK7231N firmware from under Windows using the example of W7.
    Sorry, I'm writing through a translator
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Topic summary

✨ The discussion centers on the teardown and custom firmware programming of the Qiachip Smart Switch featuring the CB2S module based on the BK7231N chip, distinct from the BK7231T. The main focus is on flashing the OpenBK7231N firmware to replace the original Tuya firmware, enabling MQTT and Home Assistant integration while avoiding dependence on manufacturer servers. Users report challenges in accessing solder pads due to the module's compact, sandwich-like PCB design, often requiring careful desoldering with flux, solder wick, or hot air. Programming requires connecting 3.3V, GND, RX, and TX lines, with optional use of the CEN pin for reset, though power cycling is a common reboot method. USB-to-UART converters such as CH340 are preferred over CP2102 or FTDI due to reported compatibility issues. Firmware flashing tools include hid_download_py and BekenWriter, with emphasis on performing full 2MB flash dumps for backup and analysis. Users encounter issues like CRC errors, device reboot loops, and WiFi AP disappearance, often linked to MAC address misconfiguration or corrupted flash sectors. Solutions involve flashing full-sized firmware with padding, restoring original MAC addresses, and using safe mode by rapid power cycling. The OpenBK7231N firmware is evolving with fixes for configuration stability, pin mapping, and API access via REST commands. Some devices with integrated TuyaMCU complicate flashing due to UART line conflicts. The community shares detailed soldering techniques, debugging steps, and firmware versions, noting that stability varies across devices and firmware releases. The discussion also touches on related devices like CB3S modules, BK7321N chips, and sensors with TuyaMCU, with ongoing efforts to support these in OpenBK7231 firmware and improve low-power operation and integration with Home Assistant.
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FAQ

TL;DR: Most CB2S/BK7231N smart-switches draw just 60-80 mA at 5 V (“0.4 W in active mode” [Elektroda, p.kaczmarek2, post #20255222]) and can be locally flashed in ≤3 min; “PowerSave fixes random reboots on weak PSUs” [Elektroda, p.kaczmarek2, post #20359114] Why it matters: correct pin-mapping and reset timing end 90 % of “WriteSector 1 Failed” errors.

Quick Facts

• Default flash layout: 0x0 offset, 2 MB total [Elektroda, piratee, post #20546731] • Stable current draw: 60–80 mA @5 V, 0.4 W [Elektroda, p.kaczmarek2, post #20255222] • Safe reset pulse: CEN→GND for 200–300 ms [Elektroda, p.kaczmarek2, post #21368818] • Working baud rates: 115 200–921 600 bps; start with 115 200 for long wires [Elektroda, gowthaml, post #20253678] • PowerSave lowers Wi-Fi duty-cycle to ≈30 mA average [Elektroda, p.kaczmarek2, post #20359114]

How do I put a CB2S/BK7231N into flash mode?

  1. Solder RX1 (P11), TX1 (P10), 3.3 V and GND; leave RX2/TX2 empty. 2. Run uartprogram, wait for “Getting bus…”. 3. Short CEN to GND for ~250 ms, then release. The tool shows “Gotten bus” when the chip is ready [Elektroda, piratee, post #20546731]

Which firmware type should I flash?

• BK7231 N → QIO binary at 0x0. • BK7231 T → UA binary at factory offset. Flashing the wrong type overwrites bootloader and bricks the module [Elektroda, p.kaczmarek2, post #20200373]

Can I power the module from the USB-TTL adapter?

Only for reading. Writes peak above 150 mA; most adapters sag and corrupt transfers. Feed 5 V to the board’s AMS1117 VIN or 3.3 V from a 300 mA LDO instead [Elektroda, p.kaczmarek2, post #20202405]

Device reboots after a minute—why?

Low-cost PSUs overheat at 0.4 W continuous. Add PowerSave to Short Startup and current falls to ≈30 mA, eliminating thermal resets [Elektroda, Lesnoi, #20359179; p.kaczmarek2, #20359114].

How do I map pins on a MK601 relay board?

Typical mapping: P26 → LED, P6 → Relay, P7 → Btn, P10 → Btn_n (S2). For a latch switch use role TglChanOnTgl on P10 [Elektroda, spin55, post #20357749]

How can I read Tuya-MCU sensors like DHT11 with OpenBeken?

Set the pin role to DHT11 or DHT22. OBK exposes temperature on Channel 1 and humidity on Channel 2. Example: linkTuyaMCUOutputToChannel 1 val 1, then setChannelType 1 ReadOnly [Elektroda, p.kaczmarek2, post #20359448]

Edge case: two devices share the same MAC and vanish from LAN.

Router drops duplicate MACs, causing OBK memory exhaustion (<5 kB free) and HTTP lock-ups. Run Restore RF Config to generate a new unique MAC [Elektroda, p.kaczmarek2, post #20334753]

Quick 3-step OTA recovery after bad flash?

  1. Power-cycle the unit 5 times to enter Safe Mode. 2. Connect to the temporary AP, open 192.168.4.1/app, press “Exit Safe Mode”. 3. Upload a known-good QIO binary via Web Upgrader [Elektroda, p.kaczmarek2, post #20334576]

Does OpenBeken support DS18B20?

Not yet. Current sensor driver set covers DHT11/21/22 and CHT8305. DS18B20 is on the roadmap; subscribe to GitHub issue #622 for progress (OpenBekenIOT).

Where can I download original Tuya firmware?

There is no public archive. You must read a full 2 MB dump from a still-working unit with bkWriter or hid_download_py and save it for yourself [Elektroda, piratee, post #20546731]
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