Oppo A9 2020 Custom Rom Work

Project Write-Up: Developing and Porting Custom ROMs for the Oppo A9 2020

1. Executive Summary

This document outlines the technical process, challenges, and requirements involved in developing Custom ROMs for the Oppo A9 2020 (codename: CPH1943). Due to Oppo’s security architecture and partition layout, this device presents significant hurdles for aftermarket development. This write-up covers the device tree structure, kernel source requirements, and the specific workarounds necessary to bypass ColorOS limitations.

1. Unlock bootloader (paid exploit).
2. Flash a GSI via fastboot or TWRP.
3. Expect bugs: MTP, camera, and proximity sensor often break.

• No Official Unlock Tool: OPPO shut down its bootloader unlock application service in 2021 for most devices, including the A9 2020.
• No Fastboot Unlock Commands: Standard commands like fastboot oem unlock do not work.
• The Only Working Method: Paid, unofficial exploits (e.g., using MTK client, SEtool, or unlocking services on forums like XDA). These are risky, may brick your device, and cost $10–$30.

• MediaTek Processor: The A9 2020 runs on the MediaTek Helio P35 (MT6765) . MediaTek is notoriously bad at releasing kernel sources (compared to Qualcomm). This makes building stable ROMs extremely difficult.
• Dynamic Partitions: Oppo uses a complex partitioning system that scares off beginner developers.
• Locked Bootloader Hassle: Oppo actively discourages unlocking bootloaders, requiring "Deep Testing" apps that take 7-10 days to approve.

Step 2: Enable USB Debugging & OEM Unlocking

Go to Settings > About Phone > Tap Build Number 7 times > Developer Options > Enable USB Debugging and OEM Unlocking. oppo a9 2020 custom rom work