What Is ISP Pinout
ISP (In-System Programming) pinout is a direct hardware access method that allows technicians to communicate with the NAND flash storage chip — in this case a UFS 2.1 module — without relying on the device's operating system or bootloader. On the Samsung SM-A426U1, the UFS chip is soldered directly to the motherboard, and its signal lines are routed to specific test pads on the PCB. By connecting a compatible ISP tool to these pads, a technician can read, write, or erase flash memory at a low level, bypassing software locks entirely. This makes ISP the last-resort solution when all software-based flashing and unlock methods have failed.
When Technicians Use ISP
ISP is typically reserved for situations where conventional repair paths are exhausted. Common scenarios on the SM-A426U1 include:
- Dead boot / hard brick: The device shows no signs of life and cannot be recognized by a PC via USB or EDL mode.
- FRP (Factory Reset Protection) lock: The Google account lock cannot be bypassed through software tools or ADB.
- Failed UFI or JTAG attempts: Previous box-based repair attempts have left the device unresponsive or have corrupted partition headers.
- Pattern or PIN lock: The device is locked and cannot be accessed through recovery or download mode.
- Firmware corruption: A failed OTA update or interrupted flash has left the bootloader or modem partitions damaged.
ISP bypasses all of these barriers by addressing the storage hardware directly.
SM-A426U1 ISP Pin Locations
The SM-A426U1 uses a Qualcomm Snapdragon 750G platform with UFS 2.1 flash storage. The ISP test pads are located on the back side of the motherboard, clustered near the UFS package. The standard UFS ISP signals to locate are CLK, CMD (DATA STROBE), DAT0–DAT3, VCC (2.9V), VCCQ (1.8V), and GND. Exact pad coordinates and silkscreen labels vary between PCB revisions and should be verified against a board-level schematic or a trusted ISP diagram image before probing. Use a high-magnification loupe or digital microscope to identify the correct pads before making contact.
Connecting to the ISP Points
Follow these steps when attaching ISP cables to the SM-A426U1 board:
- Fully disassemble the device and remove the motherboard from the chassis.
- Clean the target test pads with isopropyl alcohol (99%) and a fine brush to remove flux or oxidation.
- Tin each pad lightly with quality solder — avoid bridging adjacent pads.
- Attach a pogo pin ISP adapter or solder fine 30 AWG wire leads to each pad in the correct signal order: GND, VCC, VCCQ, CLK, CMD, DAT0–DAT3.
- Connect wires to your ISP box (e.g., Easy-JTAG Plus or UFi Box) following the tool's UFS pinout diagram.
- Power the board through the ISP tool's regulated supply — do not connect the battery during ISP work.
- Launch the ISP software, select UFS chip type, and run detection before executing any read or write operation.
Safety Tips and Precautions
Working at the ISP level carries real risk of permanent board damage if precautions are ignored:
- ESD protection: Always wear an anti-static wrist strap and work on a grounded ESD mat.
- Voltage verification: UFS VCC is 2.9V and VCCQ is 1.8V. Applying incorrect voltage will destroy the UFS chip instantly.
- No battery during ISP: Disconnect the battery completely to prevent voltage conflicts with the ISP tool's power supply.
- Backup first: Always attempt a full dump/read before any write or erase operation.
- Avoid prolonged heat: Keep soldering iron contact time under two seconds per pad to prevent UFS package delamination.
- Double-check pinout: Confirm the ISP diagram matches your exact PCB revision before applying power.
Pin / Test Point Reference
| Pin | Description |
|---|---|
| CLK | UFS clock signal test pad, located near UFS package on PCB back side — Verify pad location against board-level schematic before probing |
| CMD | UFS command / data strobe line — Also referred to as DQS in some UFS diagrams |
| DAT0 | UFS data line 0 |
| DAT1 | UFS data line 1 |
| DAT2 | UFS data line 2 |
| DAT3 | UFS data line 3 |
| VCC | Main power supply to UFS chip — 2.9V — Do not exceed rated voltage |
| VCCQ | I/O power supply to UFS chip — 1.8V — Separate rail from VCC; both required for operation |
| GND | Ground reference for all ISP signals — Use nearest ground plane via or pad |
Tools required: Easy-JTAG Plus (with UFS ISP adapter), UFi Box, UMT Pro (ISP module), Medusa Pro II, 30 AWG enameled copper wire, Digital microscope or loupe, Soldering iron with fine tip, 99% isopropyl alcohol, Anti-static wrist strap and ESD mat
Supported operations: Read Firmware / Full Dump, FRP Erase, Dead Boot Repair, Pattern / PIN Lock Removal, Partition Restore, IMEI Repair (where legally permitted)
⚠ Safety note: UFS VCC=2.9V, VCCQ=1.8V — incorrect voltage permanently destroys the UFS chip. Disconnect battery before ISP work. ESD precautions mandatory. Always read/backup before any write operation.
Comments (0)
Be the first to comment.