To never see SPD Flash Tool R400001 again:
If you’re using a clone CH341A, the original R400001 firmware might have bugs. Look for an updated version from your tool’s manufacturer—some community builds fix the timeout issue. spd flash tool r400001
Don’t rely on USB power alone if you’re programming multiple modules. Use an external 3.3V supply (max 50mA) to the VCC pin of the RAM stick. The SPD EEPROM needs clean power. To never see SPD Flash Tool R400001 again:
SPD chipsets are extremely sensitive to voltage. If your phone’s battery is below 40% or completely dead, the phone will power on just long enough to start the flash, then shut down due to undervoltage. This triggers R400001. spd flash tool r400001
This works when timing is the issue.