Add basic POC input device support and rotary encoder implementation as an example

README.md

@@ -28,7 +28,7 @@
 - **Real-time keymap editing**: RMK has built-in [Vial](https://get.vial.today) support, the keymap can be changed on-the-fly. You can even use Vial to edit keymap over BLE directly
 - **Advanced keyboard features**: Many advanced keyboard features are available by default in RMK, such as layer switch, media control, system control, mouse control, etc
 - **Wireless**: BLE wireless support with auto-reconnection/multiple devices feature for nRF52 and esp32 microcontrollers, tested on nRF52840, esp32c3 and esp32s3
-- **Easy configuration**: RMK provides a simple way to build your keyboard: a `keyboard.toml` is all you need! For experienced Rust user, you can still customize your firmware easily using RMK
+- **Easy configuration**: RMK provides a simple way to build your keyboard: a `keyboard.toml` is all you need! For experienced Rust user, you can still customize your firmware easily using Rust code
 - **Low latency and low-power ready**: RMK has a typical 2 ms latency in wired mode and 10 ms latency in wireless mode. By enabling `async_matrix` feature, RMK has very low power consumption, with a 2000mah battery, RMK can provide several months battery life
 
 ## [User Documentation](https://haobogu.github.io/rmk/user_guide/1_guide_overview.html) | [API Reference](https://docs.rs/rmk/latest/rmk/) | [FAQs](https://haobogu.github.io/rmk/faq.html) | [Changelog](https://github.com/HaoboGu/rmk/blob/main/rmk/CHANGELOG.md)

docs/po/zh_CN.po

@@ -2531,15 +2531,15 @@ msgstr ""
 
 #: src\how_to_contribute.md:41
 msgid ""
-"`key_event_channel`: a multi-sender, single-receiver channel. The sender can "
+"`KEY_EVENT_CHANNEL`: a multi-sender, single-receiver channel. The sender can "
 "be a matrix task which scans the key matrix or a split peripheral monitor "
 "which receives key event from split peripheral. The receiver, i.e. keyboard "
 "task, receives the key event and processes the key"
 msgstr ""
 
 #: src\how_to_contribute.md:42
 msgid ""
-"`keyboard_report_channel`: a single-sender, single-receiver channel, "
+"`KEYBOARD_REPORT_CHANNEL`: a single-sender, single-receiver channel, "
 "keyboard task sends keyboard report to channel after the key event is "
 "processed, and USB/BLE task receives the keyboard report and sends the key "
 "to the host."

docs/src/design_doc/input_device.md

@@ -0,0 +1,129 @@
+# Input devices
+
+The definition of input devices varies, but for RMK, we focus on two categories: keys and sensors.
+
+-	Keys are straightforward—they are essentially switches with two states.
+-	Sensors, on the other hand, are more complex. Devices such as joysticks, mice, trackpads, and trackballs are all sensors. They produce different data and speak different protocols.
+
+RMK’s input device framework is designed to provide a simple yet extensible way to handle both keys and sensors. Below is an overview of the framework:
+
+![input_device_framework](../images/input_device_framework.svg)
+
+At first glance, the framework looks simple. However, as we delve into the implementation, intricacies emerge. In this documentation, we will focus on the left half of the diagram: `InputDevices` and `InputProcessors`. Key areas of complexity include:
+
+This design document outlines the current implementation, which aims to make RMK’s input device system clear, easy to use, and extensible.
+
+## Input device trait
+
+The input devices can be key matrix or sensors, which read the physical devices, send raw events to the input processors. All input devices in RMK should implement the `InputDevice` trait:
+
+```rust
+pub trait InputDevice {
+    /// Event type that input device will send 
+    type EventType;
+
+    /// Starts the input device task.
+    ///
+    /// This asynchronous method should contain the main logic for the input device.
+    /// It will be executed concurrently with other input devices using the `run_devices` macro.
+    fn run(&mut self) -> impl Future<Output = ()>;
+
+    /// Get the event channel for the input device. All events should be send by this channel.
+    fn get_channel(&self) -> &Channel<CriticalSectionRawMutex, Self::EventType, EVENT_CHANNEL_SIZE>;
+}
+```
+
+This trait should be used with the `run_devices!` macro:
+
+```rust
+// Suppose that the d1 & d2 both implement `InputDevice`. `run()` will be called in `run_devices!`
+run_devices!(d1, d2).await;
+```
+
+> Why `run_devices!`?
+>
+> Currently, embassy-rs does not support generic tasks. So the only option is to join all tasks(aka `run` function in `InputDevice`) together. That's what `run_devices!` does.
+
+
+Another thing that need to be mentioned is that every input device defines its own `EventType`. RMK provides a default Event enum, which is compatible with built-in InputProcessors. This design balances convenience and flexibility:
+
+- For common devices, developers can use the built-in `Event` and `InputProcessor` implementations to when implementing new `InputDevice`
+- For advanced use cases, developers can define custom events and processors to fully control the input logic.
+
+## Event
+
+The event is the output of input devices. It's defined as a non-exhaustive enum:
+
+```rust
+#[non_exhaustive]
+#[derive(Serialize, Deserialize, Clone, Debug)]
+pub enum Event {
+    /// Keyboard event
+    Key(KeyEvent),
+    /// Rotary encoder, ec11 compatible models
+    RotaryEncoder(RotaryEncoderEvent),
+    /// Multi-touch touchpad
+    Touchpad(TouchpadEvent),
+    /// Joystick, suppose we have x,y,z axes for this joystick
+    Joystick([AxisEvent; 3]),
+    /// An AxisEvent in a stream of events. The receiver should keep receiving events until it receives [`Eos`] event.
+    AxisEventStream(AxisEvent),
+    /// End of the event sequence
+    ///
+    /// This is used with [`AxisEventStream`] to indicate the end of the event sequence.
+    Eos,
+}
+```
+
+The `Event` aims to include raw outputs of all commonly used input devices, such as mice, trackpads, joysticks, etc. It also provides a stream-like axis event representation `AxisEventStream`, which can be used for a multiple-axis device where the number of axes is not known. Note that when using this, the `Eos` should be sent the indicate the end of the event sequence, otherwise the `InputProcessor` would wait for the next event forever.
+
+## Input processor trait
+
+The input processors receive the event from input devices, process them and convert results to HID reports for USB/BLE transmission. All input processors should implement the `InputProcessor` trait:
+
+```rust
+pub trait InputProcessor {
+  /// Event type that the input processor receives.
+    type EventType;
+
+    /// Process the incoming events, convert them to HID report [`KeyboardReportMessage`],
+    /// then send the report to the USB/BLE.
+    ///
+    /// Note there might be mulitple HID reports are generated for one event,
+    /// so the "sending report" operation should be done in the `process` method.
+    /// The input processor implementor should be aware of this.  
+    fn process(&mut self, event: Self::EventType) -> impl Future<Output = ()>;
+
+    /// Get the input event channel for the input processor.
+    ///
+    /// The input processor receives events from this channel, processes the event,
+    /// then sends to the report channel.
+    fn get_event_channel(
+        &self,
+    ) -> &Channel<CriticalSectionRawMutex, Self::EventType, EVENT_CHANNEL_SIZE>;
+
+    /// Get the output report channel for the input processor.
+    ///
+    /// The input processor sends keyboard reports to this channel.
+    fn get_report_channel(
+        &self,
+    ) -> &Channel<CriticalSectionRawMutex, KeyboardReportMessage, REPORT_CHANNEL_SIZE> {
+        &KEYBOARD_REPORT_CHANNEL
+    }
+
+    /// Default implementation of the input processor. It wait for a new event from the event channel,
+    /// then process the event.
+    ///
+    /// The report is sent to the USB/BLE in the `process` method.
+    fn run(&mut self) -> impl Future<Output = ()> {
+        async {
+            loop {
+                let event = self.get_event_channel().receive().await;
+                self.process(event).await;
+            }
+        }
+    }
+}
+```
+
+The `process` method is responsible for processing input events and sending HID report to the report channel, which is available by `get_report_channel`.

docs/src/how_to_contribute.md

@@ -33,8 +33,8 @@ So, if you want to contribute new features of RMK, just look into `rmk` core cra
 Generally, there are 4-5 running tasks in the meanwhile, according to the user's config. Communication between tasks is done by channels.There are several built-in channels: 
 
 - `FLASH_CHANNEL`: a multi-sender, single-receiver channel. There are many tasks send the `FlashOperationMessage`, such as BLE task(which saves bond info), vial task(which saves key), etc.
-- `key_event_channel`: a multi-sender, single-receiver channel. The sender can be a matrix task which scans the key matrix or a split peripheral monitor which receives key event from split peripheral. The receiver, i.e. keyboard task, receives the key event and processes the key
-- `keyboard_report_channel`: a single-sender, single-receiver channel, keyboard task sends keyboard report to channel after the key event is processed, and USB/BLE task receives the keyboard report and sends the key to the host.
+- `KEY_EVENT_CHANNEL`: a multi-sender, single-receiver channel. The sender can be a matrix task which scans the key matrix or a split peripheral monitor which receives key event from split peripheral. The receiver, i.e. keyboard task, receives the key event and processes the key
+- `KEYBOARD_REPORT_CHANNEL`: a single-sender, single-receiver channel, keyboard task sends keyboard report to channel after the key event is processed, and USB/BLE task receives the keyboard report and sends the key to the host.
 
 ### Matrix scanning & key processing
 

docs/src/images/input_device_framework.drawio

@@ -0,0 +1,88 @@
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examples/use_rust/nrf52840_ble/Cargo.toml

@@ -34,6 +34,8 @@ embassy-executor = { version = "0.6", features = [
     "executor-thread",
     "integrated-timers",
 ] }
+embassy-futures = { version = "0.1", features = ["defmt"] }
+
 defmt = "0.3"
 defmt-rtt = "0.4"
 panic-probe = { version = "0.3", features = ["print-defmt"] }