DS5Dongle-OLED-Edition-steam-machine/CLAUDE.md

CLAUDE.md

This file provides guidance to Claude Code (claude.ai/code) when working with code in this repository.

What this is

A Raspberry Pi Pico 2 W (RP2350) firmware that bridges a Sony DualSense (DS5) controller over Bluetooth Classic to a USB host. Presents itself to the host as a USB HID + UAC1 audio composite device. This repo is MarcelineVPQ/DS5Dongle-OLED-Edition, a personal fork of upstream awalol/DS5Dongle that adds an optional Waveshare Pico-OLED-1.3 status display (10 screens) and a 4-slot persistent multi-controller pairing layer.

README.md is authoritative for user-facing capability; CHANGELOG.md tracks what shipped per release. Read both before proposing changes — much of the design is non-obvious from the code alone (audit history, BT pairing-posture rationale, overclock requirement).

Build

This is firmware — there are no tests. Verification is hardware-in-the-loop (see "Hardware-in-the-loop workflow" below).

The build is non-trivial to set up because it requires a specific TinyUSB version:

# Pico SDK 2.2.0 must be installed; export PICO_SDK_PATH.
# CRITICAL: TinyUSB must be pinned to 0.20.0. The 0.18.0 that ships with
# Pico SDK 2.2.0 lacks the 4-arg form of TUD_AUDIO_EP_SIZE used by
# src/tusb_config.h — compile errors with no clear pointer to the cause.
cd "$PICO_SDK_PATH/lib/tinyusb"
git fetch --tags && git checkout 0.20.0

# Build
cd /path/to/DS5Dongle
cmake -S . -B build -G Ninja -DCMAKE_BUILD_TYPE=Release -DPICO_SDK_PATH="$PICO_SDK_PATH"
cmake --build build --target ds5-bridge
# Produces build/ds5-bridge-oled.uf2  (output name set in CMakeLists.txt, not the default)

Common build flags (set via -D on the cmake invocation):

• ENABLE_SERIAL=ON — route printf to USB CDC for debugging. Default OFF (production).
• ENABLE_VERBOSE=ON — chatty BT/HID logging. Default OFF.
• ENABLE_BATT_LED=OFF — disable the low-battery LED blink. Default ON.
• PICO_W_BUILD=ON — build for the original Pico W (drops audio, lower clock). Default targets Pico 2 W.

CI runs four build variants in .github/workflows/build.yml (standard / debug / no-batt-led / Pico W). When changing build flags or CMake, update the workflow accordingly.

Hardware-in-the-loop workflow

There are no software tests. To verify a change:

1. Build → produces build/ds5-bridge-oled.uf2.
2. Put Pico into bootloader: hold BOOTSEL, plug USB. It mounts as /run/media/$USER/RP2350 (Linux) or RPI-RP2 (others).
3. Copy the UF2 to the mount: cp build/ds5-bridge-oled.uf2 /run/media/$USER/RP2350/ — Pico auto-reboots into the new firmware.
4. Pair a DualSense: hold Create + PS on the controller until the lightbar pulses; the dongle inquiry picks it up.
5. Verify enumeration host-side: lsusb | grep 054c:0ce6 should show Sony Corp. DualSense wireless controller (PS5).

The development cadence is one feature per UF2 + checkpoint with the user before moving on — the user has hardware in front of them, regressions are caught the same minute, and large multi-feature commits make root-causing hard.

Architecture

Two cores, asymmetric workload:

• Core 0 runs everything: main() infinite loop in src/main.cpp drives cyw43_arch_poll() → BTstack, tud_task() → TinyUSB, audio_loop() (USB → BT haptic path), interrupt_loop() (BT → USB HID path), and oled_loop().
• Core 1 runs only core1_entry() in src/audio.cpp — the Opus speaker encoder. The two cores communicate via Pico SDK queue_t (audio_fifo) and a critical section (opus_cs).

Two parallel data paths through the firmware:

1. HID (DS5 input → host, host output → DS5): src/bt.cpp registers on_bt_data() → src/main.cpp:on_bt_data() → updates interrupt_in_data[63] → tud_hid_report(). Output reports come the other way through tud_hid_set_report_cb.
2. Audio (host USB audio → DS5 speaker + haptics): src/audio.cpp:audio_loop() reads 4-channel USB UAC1, splits ch1/2 (speaker → Opus encode on core1 → BT 0x32 report) and ch3/4 (haptic → resample 48k→3k → BT 0x32 report).

BT layer: Uses Pico SDK's bundled BTstack (no separate clone). src/bt.cpp is the only file that touches HCI/L2CAP. PSMs are PSM_HID_CONTROL and PSM_HID_INTERRUPT. Link keys live in BTstack's TLV NVM with NVM_NUM_LINK_KEYS=4 (configured in src/btstack_config.h).

OLED add-on is optional and self-contained: All 10 screens, the SH1107 SPI driver, the 5×7 font, the icon table, and the input handling live in src/oled.cpp (~30 KB). The only outward dependencies are read-only accessors (bt_is_connected, bt_get_addr, audio_peak_*, bt_get_signal_strength, the new slot accessors) and the global interrupt_in_data[63] (read-only for input visualization). When no OLED is wired, the SPI writes go nowhere — no init check needed.

Multi-slot pairing (Phase G): Storage is two-tier:

• Link keys stay in BTstack's TLV NVM (4 slots, unchanged from upstream).
• bd_addrs + occupancy in a custom flash sector owned by src/slots.cpp — sector below the config sector (PICO_FLASH_SIZE_BYTES - 2*FLASH_SECTOR_SIZE).

Slot routing is enforced in src/bt.cpp's HCI_EVENT_INQUIRY_RESULT handler: skip devices owned by other slots, accept only the current slot's bd_addr if occupied, auto-assign on first L2CAP_EVENT_CHANNEL_OPENED for HID_CONTROL when the current slot is empty. Switching slots flows: bt_set_slot() → persist new index → bt_disconnect() → HCI_EVENT_DISCONNECTION_COMPLETE → restart inquiry under new filter.

Flash layout (top of flash, growing downward):

Sector	Owner	Contents
PICO_FLASH_SIZE_BYTES - 1*FLASH_SECTOR_SIZE	src/config.cpp	Config{magic, version, crc32, size, body} — 9 user-tunable fields incl. current_slot
PICO_FLASH_SIZE_BYTES - 2*FLASH_SECTOR_SIZE	src/slots.cpp	SlotsData{magic, addrs[4][6], occupied[4]}

config_save() and save_slots_to_flash() both use save_and_disable_interrupts() + flash_range_erase + flash_range_program. PICO_FLASH_ASSUME_CORE1_SAFE=1 is set in CMakeLists.txt — flash writes happen while core1 may be running, but core1's hot path (Opus encode) does not access XIP during the brief erase/program window.

Critical gotchas

These are non-obvious from the code; they cost time when forgotten.

• Overclock 320 MHz @ 1.20 V is load-bearing. Dropping voltage to 1.10 V or clock to stock breaks the CYW43 PIO SPI bus (BT chip becomes unreachable). Tested. Don't "optimize" src/main.cpp:main()'s vreg_set_voltage(VREG_VOLTAGE_1_20) + set_sys_clock_khz(SYS_CLOCK_KHZ, true) block.
• Render functions are __attribute__((noinline)) on purpose. With aggressive inlining the compiler folds all 10 render_screen_* into oled_loop(), which then exceeds Thumb's 4 KB literal-pool reach and the linker emits dangerous relocation: unsupported relocation. If you remove the noinline attributes or merge two render functions into a single huge one, the build will fail at link time. The symbol size grows over time as screens get richer — the lambda inside render_screen_settings was already hoisted to a noinline format_settings_item() for the same reason.
• config_default() is implemented in this fork, not upstream. Upstream declares it in config.h:30 but never defines it. The implementation in src/config.cpp fills the body with 0xFF and re-runs config_valid() (matches a freshly-erased flash sector). Don't assume any header declaration is implemented just because it compiles — check the .cpp.
• Screen indices are symbolic. kScreenStatus, kScreenSlots, kScreenLightbar, … are defined in a single block near the top of src/oled.cpp. oled_loop()'s switch and handle_buttons()' KEY1 contextual checks (Trigger preset cycle, Lightbar mode cycle) refer to them by name. Never hard-code integers — reorder = one-block edit.
• OLED kPin* pinout is hardcoded to the Waveshare Pico-OLED-1.3 standard (kPinMOSI=11, kPinCLK=10, kPinCS=9, kPinDC=8, kPinRST=12, kPinKey0=15, kPinKey1=17). SPI1 instance. Conflicts with anything else on those pins. Pico's BT chip uses internal SPI to CYW43 (different bus), and USB / UART pins (GP0/GP1) are also free — no conflicts in default config.
• DS5 PS+Mute hold-2-seconds → watchdog_reboot(0,0,0) is the headless soft-reboot path (see src/main.cpp:interrupt_loop()). It checks interrupt_in_data[9] bits 0+2. If you change input report layout, this combo breaks silently.
• Inactivity-disconnect uses packet[3..12] in the L2CAP interrupt data path (src/bt.cpp:l2cap_packet_handler). It's looking at sticks and DPad/buttons to decide "idle." Don't touch those bytes' layout without updating the heuristic.
• The 0x36 BT audio packet layout is load-bearing — speaker + HD haptic actuators silently die without the SetStateData sub-report. Upstream commit 3a31bd7 (May 2026, "refactor: add SetStateData and audio send priority") moved the 0x10 SetStateData block out of every audio frame and into a one-time L2CAP-open setup. The DualSense hardware requires that sub-report (specifically the 0x7f 0x7f Headphones + Speaker volume bytes) at pkt[11..75] of every 0x36 frame, or the actuators stop producing output even though USB and BT byte counts look fine. Our fork keeps state_data[63] in src/audio.cpp and re-asserts it on every frame; the pre-3a31bd7 packet layout is: state_data at pkt[11..75], haptic at pkt[76..141], speaker format at pkt[142], opus payload at pkt[144..343]. If you rebase onto an upstream that has the refactor and don't preserve this restoration, speaker + HD haptics silently break. The scripts/test_speaker.sh helper + the USB aud / BT 0x32 counters on the OLED Diagnostics screen are the regression tripwire — if bytes are flowing but you hear nothing, look at packet contents not flow. Upstream PR #93 is tracking a proper unified fix; ours is the pre-refactor revert applied just to audio.cpp. Same fix was shipped independently by loteran/DS5Dongle (commit c7a8d3c).

Git / branch model

• master (origin) = MarcelineVPQ/DS5Dongle-OLED-Edition (this fork's primary branding, what users download).
• upstream / upstream-real = awalol/DS5Dongle (read-only mirror for git fetch upstream && git rebase cycles).
• upstream-fork = MarcelineVPQ/DS5Dongle-upstream-fork (a separate cleanroom fork retained from earlier PR contributions; not the active development branch).

Commits in this repo include a Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com> trailer for AI-assisted work.

Where features live

When asked to modify behavior, the first file to read is usually one of:

• New BT pairing / connection state behavior → src/bt.cpp (HCI + L2CAP event handlers).
• New OLED screen or change to existing one → src/oled.cpp.
• New persistent config field → src/config.h (struct), src/config.cpp:config_valid() (defaults + clamping), src/oled.cpp:format_settings_item() (UI), src/oled.cpp:settings_adjust() (D-pad ▶◀ behavior). Update CHANGELOG.md.
• USB descriptor or interface change → src/usb_descriptors.cpp + src/tusb_config.h.
• Audio / haptic path → src/audio.cpp. Don't add stack arrays sized smaller than the resampler / Opus expects (this is the C1 bug that caused the long-standing "audio stuttering" issue — fix landed in upstream 5b04cbd, but the lesson stands).

Don't do these

• Don't disable the watchdog without explicit user authorization. watchdog_enable(1000, true) in src/main.cpp:main() is the safety net for hangs.
• Don't add fallbacks for missing OLED beyond what oled.cpp already does (no init checks, SPI writes harmlessly to nothing) — the firmware must boot identically with or without the display.
• Don't write a new flash sector backend without updating the static_assert(SECTOR_OFFSET % FLASH_SECTOR_SIZE == 0) pattern from slots.cpp and confirming no overlap with config.cpp's sector.
• Don't push to upstream or upstream-fork by accident — only origin/master is the personal fork's deployment target.