OpenBeken flashed on CB2S BK7231N, no AP appears after successful flash

User question

Flashed openbeken on cb2s bk7231, flashe successful but no ap to connect to

Artificial Intelligence Response

Direct answer to the question

• Most “flash OK but no AP” cases on CB2S (BK7231N) are due to one of four things: wrong binary/offset, unstable 3.3 V power, the module stuck in non-config mode due to stored Wi‑Fi credentials, or RF calibration/boot partition damage from an over‑erase.
• First checks:
  • Confirm you flashed an OpenBeken build for BK7231N and wrote it at the correct address (0x11000 for the standard QIO/UA single-image).
  • Power the module from a solid 3.3 V supply (≥300 mA), not the USB‑UART’s 3.3 V pin.
  • After power‑up, wait 30–60 s and scan on 2.4 GHz only for “OpenBK7231N_xxxx” (or “OBK_xxxx”).
  • If no AP appears, force SAFE/Config mode (5 quick power cycles or ≥10 s button hold) and read the UART boot log on the same RX/TX used for flashing (115200 baud).

Detailed problem analysis

• Firmware image and offset
  • CB2S uses BK7231N. OpenBeken releases distinct binaries for N vs T. A T build will program fine but not boot on N.
  • For the standard OpenBeken single application image (QIO/UA), the boot ROM expects the app at 0x11000. Flashing that file at 0x00000 will prevent a normal boot and you will not get an AP. Only “full flash” images go at 0x00000, and those are not the usual distribution.
• Retained configuration vs AP appearance
  • If Wi‑Fi credentials are already stored (from a previous OBK run or a reused config area), the device tries to join that SSID first and may delay AP creation. If it never associates, it should eventually fall back to AP, but that can take a while depending on retry settings.
  • SAFE/Config mode forces the AP immediately. Triggers commonly supported by OpenBeken:
  • 5 fast power cycles (off-on) in a row.
  • Holding the user button for ~10–15 s after boot until the LED starts rapid blinking (device-dependent).
• Power integrity
  • Wi‑Fi bring‑up on BK7231N produces current spikes >250 mA. Many USB‑UART dongles’ 3.3 V rails can supply only 50–100 mA; they are fine for flashing but marginal for RF. Voltage droop during RF init causes boot loops or a silent reset before AP starts.
  • Use a bench supply or a dedicated 3.3 V LDO/DC‑DC capable of ≥300 mA. Common ground with the USB‑UART is required.
• Boot/reset hardware state
  • CEN (chip enable) must be high. If the module is still on the original mains PCB, other circuitry can pull CEN or UART pins in ways that hold the chip in reset or disturb boot. If in doubt, test the module isolated from the target board.
  • After flashing, disconnect the USB‑UART RX/TX if the host board drives those pins; contention during boot can cause odd behavior.
• RF calibration area
  • The SDK uses a small calibration region near the end of flash. A “full chip erase” without a prior backup can wipe it. Symptoms in the UART log include “RF CALI FAIL” and the radio never starting, so no AP. Recent OpenBeken builds can often regenerate defaults, but not always for every device/SDK combo.
• UART diagnostics (most decisive step)
  • Use the same serial pins you used for flashing. Set 115200 8N1. Power‑cycle and capture output from reset.
  • What to look for:
  • Continuous reboots or watchdog resets: usually power or wrong image/offset.
  • Messages indicating wrong platform/build: reflash correct BK7231N build.
  • “RF init/cali fail”: calibration region issue; try a newer OBK build that recreates RF data, or restore a backup fullflash if you have it.
  • Normal OS log but no AP: the device believes it’s in STA mode; force SAFE mode or clear Wi‑Fi config from the serial console if you get a prompt.

Current information and trends

• Community reports over the last few OpenBeken releases emphasize:
  • Correct placement at 0x11000 for the standard QIO/UA images.
  • SAFE-mode recovery by rapid power cycling is widely supported and often resolves “no AP” when stale credentials block AP creation.
  • Power supply insufficiency during RF init is the most common non-firmware root cause; using a bench supply immediately changes behavior.
  • Newer OBK builds improved RF calibration self‑repair on first boot; updating to the latest build can recover units that previously showed “RF CALI FAIL.”

Supporting explanations and details

• Why offset matters: The internal bootloader expects the vector table and image header at a fixed address. If the image is placed at 0x00000 (over the bootloader or in the wrong slot), the CPU either resets quickly or runs into invalid code, so the OS never starts the Wi‑Fi stack.
• Why the AP may be delayed: On first boot with stored credentials, the STA state machine tries multiple retries/backoff intervals. Only after it concedes failure does OBK spawn the config AP.
• Why power is different for flashing vs RF: Flash programming runs the core and flash at modest clocks with Wi‑Fi off. RF bring‑up enables the PA/LNA and PLLs, creating fast load steps that a weak regulator cannot support.

Ethical and legal aspects

• Safety: Many CB2S modules live on mains-powered devices. Do not power or probe them while connected to mains. Isolate the low-voltage section or fully remove the module before UART work.
• RF compliance: Running test APs is generally fine, but modifying radio firmware on commercial devices may affect regulatory compliance if the device is returned to field use.

Practical guidelines

1. Sanity checklist (5 minutes)
   • Confirm file name contains “BK7231N” and “QIO” or “UA”.
   • Verify you wrote it at 0x11000, erase-before-write enabled for that region only (avoid full-chip erase unless you have a complete backup).
   • Power from a stable external 3.3 V source (≥300 mA). Common GND with USB‑UART.
   • Remove/disconnect from the original appliance while testing.
2. Force config AP
   • Try 5 quick power cycles, or hold the user button for ≥10 s after boot until rapid blink, then wait up to 60 s and rescan 2.4 GHz.
3. If still no AP, get the log
   • Connect serial at 115200 on the same pins used for flashing; power-cycle; capture everything from reset. Share the first 100–200 lines.
4. Known‑good reflash procedure
   • Erase only the app region that will be written.
   • Write OpenBK7231N_QIO_x.y.z.bin at 0x11000.
   • Power-cycle, wait 60 s, scan for “OpenBK7231N_xxxx”.
5. If the log shows RF calibration errors
   • Reflash the latest OpenBeken for BK7231N again (some builds recreate RF data on first boot).
   • If you have a fullflash backup, restore the RF/calibration tail region or the whole image, then reflash OBK correctly.
6. After AP appears
   • Connect to the AP, browse to 192.168.4.1, enter your 2.4 GHz SSID/PSK (ensure your router is not WPA3‑only; use WPA2 or WPA2/WPA3 mixed).
   • Note the device IP from your router and finish configuration.

Possible disclaimers or additional notes

• Some host PCBs drive UART or boot‑related pins during power‑up and can prevent normal boot. If logs look wrong or pins are busy, lift the module or isolate its pins.
• If the module was fully erased and refuses to recreate RF data, recovery may require a donor calibration block or factory firmware—possible only if you have backups.

Suggestions for further research

• Review the OpenBeken release notes for BK7231N regarding RF calibration handling and SAFE‑mode triggers.
• Check device‑specific templates/pinouts for your product model to wire the button/LED correctly for easier recovery.
• Consider adding a small bulk capacitor (e.g., 47–100 µF near VDD) when powering the module off long wires during bench tests to absorb RF current steps.

Brief summary

• Reflash the correct BK7231N image at 0x11000, power the module from a robust 3.3 V source, and force SAFE/Config mode to bring up the AP. If that fails, capture the UART boot log; it will quickly reveal whether you’re facing a wrong build/offset, power issue, stale credentials, or RF calibration damage.

If you can, please share:

• Exact firmware filename you used and the write address.
• Flashing tool and settings (erase mode).
• How you’re powering the module.
• Whether the device is still on its original PCB.
• A boot log (115200 baud) from power‑up.

Disclaimer: The responses provided by artificial intelligence (language model) may be inaccurate and misleading. Elektroda is not responsible for the accuracy, reliability, or completeness of the presented information. All responses should be verified by the user.