What Is ISP Pinout

ISP (In-System Programming) is a hardware-level technique that allows technicians to communicate directly with the NAND flash storage on the Samsung SM-A426W motherboard, bypassing the main CPU and operating system entirely. By locating and probing dedicated test pads tied to the UFS or eMMC bus, a compatible programmer can read, write, or erase the device's storage at the chip level. For the SM-A426W, this method is particularly valuable because standard software-based tools may be blocked by a locked bootloader, corrupted firmware, or a non-functional device state. ISP gives technicians a low-level, reliable pathway to restore or interrogate the flash memory without needing the device to boot.

When to Use ISP

ISP is the recommended approach in the following situations:

  • Dead boot / no power: The device powers on but fails to reach the bootloader or download mode, making USB-based flashing impossible.
  • Locked or tripped bootloader: Security flags prevent standard Odin or EDL flashing from completing successfully.
  • Failed OTA or Odin flash: A partial or corrupted flash has left the device in a boot loop or hard-brick state.
  • FRP / Google account lock: The device is locked to a previous owner's account and cannot be unlocked via standard menus.
  • ISP is also used for full NAND dumps for backup or forensic purposes when software extraction is not possible.

SM-A426W ISP Test Points

The SM-A426W uses a Qualcomm Snapdragon 750G SoC paired with UFS 2.1 storage. The UFS interface uses a differential serial bus rather than a parallel eMMC bus, meaning the accessible ISP pads differ from classic eMMC devices. The primary test points are located on the rear side of the motherboard near the UFS storage IC. Exact pad coordinates vary by PCB revision and have not been independently verified for public publication; consult your programmer software's device library for the validated pad map before probing.

  • GND – Common ground reference point
  • VCC – Primary storage supply voltage (typically 2.9V for UFS)
  • VCCQ – I/O logic voltage (typically 1.8V)
  • DATA+ / DATA− – UFS differential data lines
  • CLK+ / CLK− – UFS differential clock lines
  • RST – Reset line to storage IC

Connecting the ISP Adapter

Before beginning, power off the device completely and remove the battery. Clean the target test pads with isopropyl alcohol (99%) and a soft brush. Use a fine-tip soldering iron set to approximately 320°C to tack 30 AWG wire or a spring-pin ISP adapter to each pad. Verify continuity with a multimeter before connecting to the programmer. Attach the wired adapter to your programmer's ISP socket, ensuring correct pin mapping as shown in your tool's device library. Apply power through the programmer only — do not reconnect the battery. Launch your programmer software, select the SM-A426W or its Snapdragon 750G UFS profile, and initiate the desired operation.

Safety Tips and Precautions

Incorrect connections can permanently destroy the UFS IC or the SoC. Always observe the following precautions:

  • Never exceed 1.8V on VCCQ lines or 2.9V on VCC lines.
  • Use an ESD wrist strap and anti-static mat throughout the procedure.
  • Double-check every wire before applying programmer power.
  • Do not connect the device battery while the programmer is powering the board.
  • Work in a dry, low-humidity environment to prevent electrostatic discharge.
  • Use a thermal camera or voltage probe to confirm no short circuits exist before powering up.

Pin / Test Point Reference

PinDescription
GNDCommon ground reference; multiple points available on PCB edge. — Verify with multimeter continuity mode
VCCPrimary UFS storage supply voltage, typically 2.9V. — Do not exceed rated voltage
VCCQUFS I/O logic voltage, typically 1.8V. — Critical — overvoltage destroys UFS IC
DATA+UFS differential positive data line to storage IC. — Pad location uncertain — verify via programmer device library
DATA−UFS differential negative data line to storage IC. — Pad location uncertain — verify via programmer device library
CLK+UFS differential positive clock line. — Pad location uncertain — verify via programmer device library
CLK−UFS differential negative clock line. — Pad location uncertain — verify via programmer device library
RSTReset signal line to UFS storage IC. — May not be required by all programmers

Tools required: EasyJTAG Plus, UFI Box, Medusa Pro II, RIFF Box 2, 30 AWG enameled wire, Fine-tip soldering iron (320°C), Digital multimeter, IPA 99% cleaning solution, ESD wrist strap and mat

Supported operations: Full NAND / UFS Dump, Firmware Read, Firmware Write / Restore, FRP Erase, Dead Boot Repair, IMEI Repair (where legally permitted), Bootloader Unlock Bypass

⚠ Safety note: UFS VCCQ is 1.8V — overvoltage permanently destroys the storage IC and SoC. Always disconnect the battery before connecting a programmer. Use ESD protection throughout.