Initial import: Rust BLE-MIDI keypad for Pico W

Port of the C/BTstack BLE-MIDI keypad firmware to Rust (embassy + cyw43 +
trouble). 16-pad RGB keypad (APA102 SPI + I2C button expander), BLE-MIDI 1.0
GATT server (full codec: sysex, running-status, real-time), octave display
on BOOTSEL, onboard LED heartbeat, USB serial logging.

- src/keypad.rs      Pimoroni RGB Keypad driver
- src/midi_keypad.rs pad->Note On/Off + LED response state machine
- src/codec.rs       BLE-MIDI 1.0 codec (port of rppicomidi, MIT)
- src/main.rs        cyw43 BT bring-up + trouble GATT + MIDI pump
- src/octave.rs      octave digit display on BOOTSEL

GPL-3.0-or-later; codec.rs retains its MIT (rppicomidi) attribution.

Cargo.toml

@@ -0,0 +1,54 @@
+[package]
+name = "rgb-keypad"
+version = "0.1.0"
+edition = "2021"
+resolver = "2"
+
+[dependencies]
+embassy-executor = { version = "0.10", default-features = false, features = ["platform-cortex-m", "executor-thread", "defmt", "executor-interrupt"] }
+embassy-time = { version = "0.5", default-features = false, features = ["defmt", "defmt-timestamp-uptime"] }
+embassy-rp = { version = "0.10", features = ["defmt", "unstable-pac", "time-driver", "critical-section-impl", "rp2040"] }
+embassy-sync = { version = "0.8", features = ["defmt"] }
+embassy-futures = "0.1.2"
+embassy-usb = { version = "0.6", default-features = false, features = ["defmt"] }
+embassy-usb-logger = { version = "0.6", default-features = false }
+log = "0.4"
+
+# BLE: cyw43 (CYW43439 BT controller on Pico W) + trouble (BLE host / GATT).
+# trouble-host 0.8.0 is unreleased on crates.io, so we pull it from git; it must
+# match the bt-hci version used by cyw43, hence the embassy/cyw43 git patch
+# below pins everything to a known-compatible revision (the same one the
+# upstream rp-pico-w example uses).
+trouble-host = { git = "https://github.com/embassy-rs/trouble", rev = "4eea72088fdbb91326a3ac95160b3154fdff802a", features = ["derive", "gatt", "defmt", "default-packet-pool-mtu-128"] }
+cyw43 = { version = "0.7", features = ["defmt", "firmware-logs", "bluetooth"] }
+cyw43-pio = { version = "0.10", features = ["defmt"] }
+
+defmt = "1.0"
+defmt-rtt = "1.0"
+panic-probe = { version = "1.0", features = ["print-defmt"] }
+
+cortex-m = { version = "0.7.6" }
+cortex-m-rt = "0.7.0"
+static_cell = "2"
+portable-atomic = { version = "1.5", features = ["critical-section"] }
+heapless = "0.8"
+
+embedded-hal-async = "1.0"
+
+[profile.release]
+debug = 2
+opt-level = "s"
+
+# Pin the embassy + cyw43 crates to the same git revision the upstream
+# rp-pico-w Bluetooth example validates, so cyw43's bt-hci and trouble's
+# bt-hci unify on one version (released crates pull incompatible bt-hci majors).
+[patch.crates-io]
+cyw43 = { git = "https://github.com/embassy-rs/embassy.git", rev = "3cd51e6d8eb6aff8b0d64d9e56a75a538bcfc65a" }
+cyw43-pio = { git = "https://github.com/embassy-rs/embassy.git", rev = "3cd51e6d8eb6aff8b0d64d9e56a75a538bcfc65a" }
+embassy-rp = { git = "https://github.com/embassy-rs/embassy.git", rev = "3cd51e6d8eb6aff8b0d64d9e56a75a538bcfc65a" }
+embassy-sync = { git = "https://github.com/embassy-rs/embassy.git", rev = "3cd51e6d8eb6aff8b0d64d9e56a75a538bcfc65a" }
+embassy-executor = { git = "https://github.com/embassy-rs/embassy.git", rev = "3cd51e6d8eb6aff8b0d64d9e56a75a538bcfc65a" }
+embassy-time = { git = "https://github.com/embassy-rs/embassy.git", rev = "3cd51e6d8eb6aff8b0d64d9e56a75a538bcfc65a" }
+embassy-usb = { git = "https://github.com/embassy-rs/embassy.git", rev = "3cd51e6d8eb6aff8b0d64d9e56a75a538bcfc65a" }
+embassy-usb-driver = { git = "https://github.com/embassy-rs/embassy.git", rev = "3cd51e6d8eb6aff8b0d64d9e56a75a538bcfc65a" }
+embassy-usb-logger = { git = "https://github.com/embassy-rs/embassy.git", rev = "3cd51e6d8eb6aff8b0d64d9e56a75a538bcfc65a" }