feat: tri-mode BLE dongle

.github/ci/_lib.sh

@@ -52,13 +52,18 @@ RMK_FEATURESETS=(
     "rynk,_ble,split,storage,async_matrix"
     "rynk,storage"
     "rynk"
+    "rynk,_ble,storage"
+    "dongle,_ble,storage"
+    "dongle,rynk,split,_ble,storage"
+    "dongle,vial,_ble,storage"
 )
 
 # Behavioral coverage only; RMK_FEATURESETS remains the compile/clippy matrix.
 RMK_TEST_FEATURESETS=(
     ""
     "vial,host_lock,_no_usb,steno,passkey_entry"
     "rynk,_ble,split,async_matrix,storage"
+    "dongle,_ble,storage"
 )
 
 # Examples auto-discovery skiplist. Reasons:
@@ -78,6 +83,14 @@ EXAMPLE_SKIPLIST=(
     "examples/use_rust/sf32lb52x_ble"
 )
 
+# Multi-target examples (several boards in one directory) sit one level
+# deeper than the discovery glob; list their crates explicitly.
+EXTRA_EXAMPLE_MANIFESTS=(
+    "examples/use_rust/nrf_dongle/dongle/Cargo.toml"
+    "examples/use_rust/nrf_dongle/central/Cargo.toml"
+    "examples/use_rust/nrf_dongle/peripheral/Cargo.toml"
+)
+
 # Echoes Cargo.toml paths for every buildable example, one per line.
 # A buildable example is a direct child of examples/use_{rust,config}/ that
 # has both a src/ dir and a Cargo.toml (filters out placeholders like fix/),
@@ -96,6 +109,10 @@ list_example_manifests() {
         done
         (( skip == 0 )) && printf '%s\n' "${dir}Cargo.toml"
     done
+    local extra
+    for extra in "${EXTRA_EXAMPLE_MANIFESTS[@]}"; do
+        [[ -f "$extra" ]] && printf '%s\n' "$extra"
+    done
 }
 
 # Echoes the default build target triple declared in the manifest's sibling

docs/docs/main/docs/development/roadmap.md

@@ -49,10 +49,10 @@ There are a bunch of things to do with RMK in the near future. I plan to ship 1.
 - [x] Stabilizing BLE feature gate/API
 - [x] Support more MCUs, such as cyw(used in rp2040w/rp2350w)
 - [ ] Deep-sleep mode
-- [x] Better support for dongle
+- [x] Better support for split dongle (dongle as the split central)
 - [ ] Nordic Uart HCI support
 - [ ] Send report via Uart/Usart
-- [ ] Switch between dongle mode and BLE mode
+- [ ] 🔵 Tri-mode dongle: switch between USB, BLE and dongle mode (see [Dongle Mode Design](./dongle_mode_design.md))
 
 #### User experience
 

examples/use_rust/nrf_dongle/README.md

@@ -0,0 +1,30 @@
+# Tri-mode dongle, end to end
+
+The complete setup from the tri-mode dongle design
+(`docs/docs/main/docs/development/dongle_mode_design.md`): a split BLE keyboard
+whose central is an ordinary `rynk` BLE keyboard, relayed to the host by a USB
+dongle. Three firmwares, one per board:
+
+| Crate | Board | Role |
+| --- | --- | --- |
+| [`dongle/`](dongle/) | nRF54LM20A | USB dongle: relays bonded keyboards (HID + Rynk CDC) |
+| [`central/`](central/) | nRF52833 | Split central: the keyboard itself (`rynk` + `split`) |
+| [`peripheral/`](peripheral/) | nRF54L15 | Split peripheral: the other half |
+
+Each crate builds independently (`cargo build --release` inside it) and flashes
+via J-Link (`./run.sh <elf>`).
+
+## Bring-up order
+
+1. Flash all three. Both keyboard halves use their DK buttons as a 2x2 matrix;
+   the central's Button 4 is the dongle key (`User8`).
+2. The split halves find each other on their own (central scans, peripheral
+   advertises).
+3. Press the dongle key on the central to switch to the dongle slot, then
+   power-cycle (reset) the dongle: its 30s pairing window picks up the seeking
+   central and pairs. From then on everything reconnects automatically.
+4. Typing from either half arrives on the host through the dongle; a Rynk host
+   tool on the dongle's CDC port reaches the central's keymap transparently.
+
+Holding the dongle key for 5s clears the central's dongle bond (or, while the
+dongle link is up, authorizes pairing a second keyboard).

examples/use_rust/nrf_dongle/central/.cargo/config.toml

@@ -0,0 +1,9 @@
+[target.'cfg(all(target_arch = "arm", target_os = "none"))']
+# runner = "probe-rs run --chip nrf52833_xxAA"
+runner = "./run.sh"
+
+[build]
+target = "thumbv7em-none-eabihf"
+
+[env]
+DEFMT_LOG = "debug"