StealthMiner – USB Device Not Recognized

Move the device to a rear-panel USB-2 port directly on a desktop motherboard. No hub, no front panel, no docking station, no USB-C-to-A dongle. This single change recovers the majority of `Device Descriptor Request Failed` cases on `CP2102` and `CH340G` bridges. If you only have a laptop available, borrow a desktop tower for 60 seconds to confirm the device is alive — that result alone tells you whether to chase the host or the device.

Swap the USB cable for one you know carries data — a cable that has successfully synced a phone or transferred files from an external SSD. Phone-wall-wart USB-C cables are charge-only roughly 40% of the time; cheap USB-A-to-Micro cables shipped with $5 electronics are unreliable too. Buy a USB-IF-certified cable for ~$10 and stop guessing every time you bench a miner.

Reboot the host PC. Trivial but real — Windows USB enumeration state can wedge after a previous failed plug, especially across sleep/resume cycles. A clean reboot clears the state. Don't skip this step just because it feels too simple; we see senior repair techs who skipped it spend 90 minutes chasing a phantom hardware fault.

Try a different host machine for 60 seconds. Borrow a partner's laptop, a friend's desktop, anything. Plug the device into a rear USB-2 port on that machine. If the device enumerates there, you've isolated the fault to your original host (driver / hub / OS state). If it fails on every host, the device is the problem and you proceed to harder steps.

Hold the recovery / `BOOT` button while plugging in. On USB-stick miners with a recovery tactile switch, pressing it during connect forces ROM-bootloader mode at the silicon level — bypassing any flashed-firmware crash. Hold for 3 seconds after plug-in, then release. The StealthMiner heater UART path doesn't have this option (the bridge chip is independent of the miner MCU), so this step applies only to USB-stick miners.

Install the matching USB-to-UART bridge driver. For `CP2102` devices: Silicon Labs CP210x VCP driver. For `CH340G`: WCH `CH341SER` driver. For `FTDI FT232R`: FTDI VCP driver. Modern Windows 10/11 and Linux kernels ship these built-in, but Windows 7, Windows 8.1, macOS Sequoia 15+ (which broke `CP2102` signing for a window of releases), and some legacy Linux distros need them installed manually. Reboot after install on Windows and macOS.

Reset the Windows USB stack. Device Manager → find the unknown / yellow-flagged device → right-click → Uninstall device → check `Delete the driver software for this device` if offered → unplug → reboot → re-plug. Stale enumeration state in the Windows USB stack causes persistent code `43`; this is the only reliable way to clear it short of a full system restore.

Move to a powered USB-2 hub. USB-stick `BM1397` miners pull `1.0 - 2.1 A` continuous, but a USB-2 motherboard port supplies `500 mA` and USB-3 supplies `900 mA`. Any USB-stick miner without a powered hub is undersized. Buy a `2.4 A`-per-port powered hub (Anker, Sabrent, Plugable) with a real `60+ W` brick. Plug the miner into the powered hub, plug the hub into the host's rear USB-2 port. This step alone resolves most intermittent-disconnect reports.

Multimeter check `VBUS` at the device input. Probe between the USB-A shell `VBUS` pin and `GND` while plugged in. Expected: `4.6 - 5.1 V`. Below `4.5 V` = cable VBUS damage or upstream port starvation. Swap cable, swap hub, re-test. If `VBUS` is good but the device still doesn't enumerate, the fault is downstream — D+/D- signalling or the bridge IC.

Add your user to `dialout` group on Linux: `sudo usermod -aG dialout $USER` then logout/login. Without this, even an enumerated `/dev/ttyUSB0` will refuse to open for cgminer running as your user. On Windows, check that no other application (PuTTY left open, Arduino IDE, ESP flasher tool) is holding the COM port. On macOS, check System Settings → Privacy & Security for the Silicon Labs System Extension approval prompt.

Wire a known-good `3.3 V` USB-to-TTL adapter to the StealthMiner Loki control board UART pads. Power off the unit. Locate the `UART_TX`, `UART_RX`, `GND` pads on the Loki control board (silkscreen labelled — typically a 3- or 4-pin header near the eMMC). Use FTDI Basic Breakout 3.3 V or equivalent — never a 5 V TTL adapter (will damage the `3.3 V` UART pins). Wire host `TX → board RX`, host `RX → board TX`, host `GND → board GND`. Power up. Open a serial terminal at `115200 baud, 8N1` — you should see u-boot output followed by Linux kernel boot.

Recover bricked StealthMiner via u-boot TFTP. Interrupt the u-boot countdown by pressing any key during the `Hit any key to stop autoboot` prompt. Run `printenv` to dump the current boot environment (capture this for D-Central support). Set `setenv ipaddr 192.168.1.99; setenv serverip 192.168.1.1` (adjust for your LAN). Run `tftp 0x80000000 boot.scr` to load a recovery script from your TFTP server. This is real bench work — only attempt if you're comfortable with embedded Linux recovery and have a TFTP server staged.

Replace a damaged or counterfeit `CP2102` / `CH340G` bridge IC on a USB-stick miner. Hot-air rework, preheat 150 °C bottom side, top-side 290-310 °C for 30 s. Order verified-genuine replacement from Mouser or Digi-Key — never a marketplace seller for these chips. Match the package: `CP2102` = `SOIC-28`, `CH340G` = `SOIC-16`. Reflow, re-test enumeration. This is the most common Tier-3 repair on USB-stick miners that have run continuously for 12+ months.

Reflash the StealthMiner control board firmware over UART when u-boot is alive but rootfs is corrupt. Use the matching VNish or Loki firmware image — D-Central can supply the correct image for your StealthMiner edition (S17 / S19 / S19j Pro / S19k Pro hashboard). Verify hardware revision before flashing; the wrong image bricks the unit further. Image is loaded via `tftp` to RAM, then written to eMMC via `mmc write`.

Check ESP32 / MCU eFuse status if a USB-stick miner uses an ESP32-based controller and ROM-mode is silent. Run `espefuse.py --chip esp32 summary` over UART. If `DIS_USB_JTAG`, `USB_PHY_SEL`, or any USB-disabling fuse is non-zero, the native USB peripheral has been permanently disabled at the silicon level. Recovery is UART-only forever — not a USB problem you can solve at any tier without chip replacement.

Stop DIY: bridge IC is visibly damaged, counterfeit-suspected, or replacement reflow has failed; eFuse permanent fault detected; StealthMiner Loki u-boot silent on UART even with a known-good FTDI adapter; or you've exhausted Tier 1-3 across two different host machines and the device still won't enumerate. Book a D-Central ASIC Repair slot.

D-Central bench process: USB-stick miners get bridge IC replacement with verified-genuine parts, firmware re-flash, calibration, and 24-hour burn-in. StealthMiner heaters get Loki control board recovery via JTAG, eMMC re-imaging from known-good golden image, hashboard validation on test fixture, and full-system noise + thermal re-tune to factory spec. We test on the bench what the manufacturer test fixtures test on the bench.

Ship safely. USB-stick miners: anti-static bag in a small padded envelope. StealthMiner heater: original packaging if possible, otherwise double-box with `≥ 5 cm` foam on every side. Include a note with observed symptoms, host OS version, USB topology that failed (port, hub, cable), and any diagnostic output you captured (Device Manager screenshot, `dmesg` capture, `lsusb` output). Saves diagnostic time and your repair cost.