Odin 3 — Retroid Dual Screen (RDS) Fixes

Fixes for using the Retroid Dual Screen (RDS) add-on with the Ayn Odin 3. It corrects the inverted touch axis and stops the touch and screen/video from cutting out — both applied automatically at boot.

Problem	Status	How
Touch Y-axis is inverted (press top, registers bottom; X is fine)	✅ Fixed	rds_yflip virtual touchscreen, Y-flipped, bound to the RDS display
Touch and screen/video cut out after ~1 min idle (had to replug)	✅ Fixed	pin USB power so the RDS never runtime-autosuspends — this was the real cause of both the touch and the screen/video dropping

Why the axis isn't a one-line setting: the RDS panel reports Y inverted in hardware — a vertical mirror, which cannot be undone by a display rotation (180° flips both axes), an IDC file (no axis-invert key), or a devicetree flag (the panel is USB-HID, not a DT device). It must be flipped in user space before Android sees it. Full write-up: docs/how-it-works.md.

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What it does

A Magisk service runs at every boot and:

1. Pins USB power — disables runtime autosuspend on all USB devices and re-pins on replug, so the RDS touch panel and its DisplayPort video (same USB-C cable) never cut out. (Root cause: the RDS USB device defaults to a 60 s autosuspend delay; the kernel suspends it after 60 s idle, killing touch + video until a replug.)
2. Corrects the touch axis — a tiny native daemon (rds_yflip, ~11 KB) grabs the RDS panel (EVIOCGRAB) and re-emits a uinput virtual touchscreen with Y flipped, bound to the RDS display via an IDC. It self-attaches on RDS replug and is restarted if it ever exits.

• ✅ Correct touch on the RDS second screen
• ✅ No more touch/video cut-out
• ✅ Survives reboot and RDS unplug/replug
• ✅ No app changes, no recompiled ROM, negligible overhead

Requirements

• Ayn Odin 3 with the Retroid Dual Screen add-on
• Root via Magisk
• For the ADB install method: a computer with adb

⚠️ The RDS shares the Odin 3's USB-C port. Plugging in a USB cable for ADB disconnects the RDS (display and touch). Do ADB work over Wireless debugging while the RDS is attached — see Connecting over Wi-Fi.

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Install

Option A — Magisk module (recommended)

1. Build the flashable zip (or just zip the magisk-module/ folder contents):

   scripts/build-magisk-zip.sh        # produces odin3-rds-touch-fix-magisk.zip

2. Copy it to the Odin, open Magisk → Modules → Install from storage, pick the zip.
3. With the RDS connected, reboot. Both fixes activate on boot; the module auto-detects your RDS display, so no per-device config is needed.

Option B — ADB install (no module flashing)

With the RDS connected and the device reachable over Wireless ADB:

scripts/install-adb.sh                # or: scripts/install-adb.sh <ip:port>

Pushes the binary, writes the display-bound IDC, installs both service.d boot scripts (USB pin + remapper), and starts everything immediately — no reboot needed to test.

Option C — Build from source

The prebuilt binary in prebuilt/rds_yflip is a dynamic aarch64 executable using only /system libraries, so it runs on a stock Odin 3. To rebuild, in a normal Termux session on the device:

pkg install -y clang
clang -O2 -o rds_yflip src/rds_yflip.c

Then place it at prebuilt/rds_yflip (Option B) or magisk-module/rds_yflip (Option A) and reinstall. (Only the axis daemon is compiled; the USB pin is a shell script.)

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Verify

After install, touch the RDS: top→bottom should track correctly, and touch should no longer cut out when idle. Over Wi-Fi ADB:

adb shell su -c 'pgrep -x rds_yflip'                         # remapper PID = running
adb shell su -c 'pgrep -f usbpin.sh'                         # USB-pin loop = running
adb shell su -c 'sh /data/adb/.../tools/usb-status.sh'       # or push tools/usb-status.sh
adb shell su -c 'tail /data/local/tmp/rds_yflip.log'         # "grabbed /dev/input/eventN"

tools/usb-status.sh should show the RDS device (vid=222a) as ctrl=on status=active asd=-1.

Uninstall

• Magisk module: remove it in the Magisk app and reboot.
• ADB install: scripts/uninstall-adb.sh [ip:port].

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If the screen ever still drops

The screen/video cut-out and the touch cut-out turned out to be the same root cause — USB autosuspend on the shared USB-C cable — so the USB-pin fix resolves both. (An earlier theory blamed a display-group doze / DP link that won't re-train; that was never reproduced once autosuspend was pinned.)

If you ever do see the RDS drop despite the pin, tools/rds_dpwatch.sh (install as a boot service) and tools/rds_capture_now.sh (run at the moment of a drop) capture DP link status + dmesg + logcat to /data/local/tmp/ for diagnosis — open an issue with the output. For reference, moving the RDS to its own display group (extend/desktop mode) is not viable on this ROM: force_desktop_mode_on_external_displays=1 crashes, and the Android 15 desktop-windowing flags are read-only.

Connecting over Wi-Fi

USB disconnects the RDS, and classic adb tcpip 5555 resets on reboot, so use Android 11+ Wireless debugging:

adb pair <ip>:<pairingPort>     # Settings → Developer options → Wireless debugging → Pair (6-digit code)
adb connect <ip>:<connectPort>  # the IP:port shown on the Wireless debugging screen

Troubleshooting

Symptom	Fix
Touch became an axis swap ("X is Y")	The IDC's touch.orientationAware isn't 0, or the IDC wasn't applied. Reinstall; ensure /data/system/devices/idc/Vendor_222a_Product_0002.idc exists and the daemon restarted after it was written.
Touch does nothing on the RDS	Virtual device not bound to the RDS display. Make sure the RDS was connected when the IDC was written; reconnect and reboot.
Still inverted after reboot	Daemon didn't start. tail /data/local/tmp/rds_yflip.log; confirm the Magisk service / service.d script is present.
Touch/video still cuts out	Check pgrep -f usbpin.sh and tools/usb-status.sh — the RDS device should be ctrl=on.
Pad/keys dead in a game (not touch)	Unrelated: check the Odin isn't in gamepad-to-mouse mode (settings get system global_gamepad_to_mouse_mode, toggled by L3).
Your panel needs X inverted or axes swapped	Pass --invert-x / --swap-xy in the boot service (see Tuning).

Do not kill the daemon with pkill -f rds_yflip — -f matches your own command line (which contains "rds_yflip") and kills your shell. Use pkill -x rds_yflip.

Repository layout

src/rds_yflip.c          axis remapper source (MIT)
prebuilt/rds_yflip       prebuilt aarch64 binary (system-libs only)
magisk-module/           flashable Magisk module — service.sh (boot), usbpin.sh, rds_yflip, IDC
scripts/                 install/uninstall/build helpers + rds_usbpin.sh
tools/                   usb-status.sh + screen-dropout diagnostics (rds_dpwatch.sh, rds_capture_now.sh)
docs/how-it-works.md     deep dive: diagnosis + design

Prebuilt binary SHA-256: b006e310ffcc73b23c6617147331eee8141ec64fc7db07461cbcc8802f350349

Notes & scope

• Verified on an Ayn Odin 3 (Android 15, Magisk) with the Retroid Dual Screen. RDS touch panel id is 222a:0001.
• The Y-inversion and the USB-autosuspend behaviour appear to be properties of the RDS hardware/firmware, so both fixes should apply to any Odin 3 + RDS. Other hosts exposing the same panel may work too (adjust --vid/--pid if needed).
• The USB pin disables runtime autosuspend on all USB devices (a tiny idle-power cost) — the simplest reliable way to keep the RDS alive.
• Community tool, not affiliated with Ayn or Retroid. Use at your own risk; root mods can affect your device. LICENSE (MIT).

Contributing

Issues and PRs welcome — confirmations on other ROM versions, a real fix for the screen-doze dropout, a proper --swap-xy range swap, and packaging improvements.