Once you’ve flashed your ROM or backed up the NV data, revert the security settings:
bcdedit /set testsigning off
bcdedit /set nointegritychecks off
Reboot. Watermark gone. Secure boot happy.
The Problem: You have an old phone (think 2012-2015) with a Spreadtrum or RDA (RDA Microelectronics) chipset—often branded "Coolsand." You plug it into your sleek Windows 11 or 10 64-bit PC to flash a custom ROM or recover a dead device. Windows dings. But nothing happens. Or worse: "Device descriptor request failed."
The Reality: Official support for these legacy Chinese SoCs died before Cortana was born. Modern Windows blocks unsigned drivers. But where there's an old phone, there's a way.
Here is your battle plan to resurrect communication with that RDA baseband chip on 64-bit Windows 10.
Q: Does this driver work on Windows 11 64-bit?
A: Partially. Windows 11 has stricter HVCI (Memory Integrity). You must disable Core Isolation → Memory Integrity in Windows Security, then follow the same Test Mode steps.
Q: I have a CoolSand RDA 8851 – is this driver compatible?
A: Yes. The driver uses generic USB classes (CDC ACM) and works across RDA 88xx series, including 8851, 8852, 8810, and 8811.
Q: The driver installs, but my phone keeps disconnecting.
A: Most likely a power management issue. Go to Device Manager → Universal Serial Bus controllers → right-click each “Root Hub” → Properties → Power Management → uncheck “Allow the computer to turn off this device”.
Q: Can I use this driver for data recovery from a dead screen?
A: Only if the phone already boots to Download Mode blindly or if you can enter preloader via key combos. For standard MTP file transfer, you need ADB drivers, not RDA USB drivers.
Original .inf files may lack NTamd64 section. Add the following under [Manufacturer]:
[Manufacturer]
%MfgName% = RDAUSB, NTamd64
And under [RDAUSB.NTamd64]:
%USB\VID_18D1&PID_0001.DeviceDesc% = RDAUSB, USB\VID_18D1&PID_0001
Note: Replace VID/PID with actual device hardware ID from Device Manager → Details → Hardware Ids.
Before proceeding, understand the obstacles:
The CoolSand RDA (RDA Microelectronics) USB driver is essential for establishing communication between Windows-based development tools and RDA chipsets (commonly found in feature phones, IoT modules, and legacy mobile devices). However, the original drivers were designed for 32-bit Windows XP/Vista/7 and lack native support for 64-bit Windows 10, particularly due to driver signature enforcement (DSE) and deprecated legacy APIs. This paper documents a method to successfully install and operate the CoolSand RDA USB driver on 64-bit Windows 10, including disabling driver signature enforcement, manually installing legacy hardware, and verifying COM port enumeration.
When attempting to install the CoolSand RDA driver on Windows 10 x64, users commonly encounter: