Add build features

.vscode/tasks.json

@@ -0,0 +1,25 @@
+{
+	"version": "2.0.0",
+	"tasks": [
+		{
+			"type": "cargo",
+			"command": "run",
+			"problemMatcher": [
+				"$rustc"
+			],
+			"label": "rust: Install to Pico (Mouse HID)"
+		},
+		{
+			"type": "cargo",
+			"command": "run",
+			"args": [
+				"--features",
+				"serial"
+			],
+			"problemMatcher": [
+				"$rustc"
+			],
+			"label": "rust: Install to Pico (Serial HID)"
+		}
+	]
+}

Cargo.toml

@@ -18,3 +18,6 @@ embedded-hal = "0.2.7"
 fugit = "0.3.6"
 numtoa = "0.2.4"
 usbd-serial = "0.1.1"
+
+[features]
+serial = []

src/main.rs

@@ -1,15 +1,19 @@
 #![no_std]
 #![no_main]
 
-extern crate alloc;
-
+#[cfg(features = "serial")]
 mod custom_hid;
+
+#[cfg(not(features = "serial"))]
 mod mouse_hid;
+
 mod mouse_sensor;
 mod serial;
 
-use alloc::boxed::Box;
+#[cfg(features = "serial")]
 use custom_hid::CustomHID;
+
+#[cfg(not(features = "serial"))]
 use mouse_hid::MouseHID;
 
 // Ensure we halt the program on panic (if we don't mention this crate it won't
@@ -26,8 +30,6 @@ use bsp::{
 
 use crate::mouse_sensor::MouseSensor;
 
-const SERIAL: bool = true;
-
 pub trait MouseInfoSender {
     fn send(&mut self, x: i8, y: i8, buttons: u8, wheel: i8, pan: i8);
 }
@@ -56,23 +58,23 @@ fn main() -> ! {
 
     let peripheral_clock = clocks.peripheral_clock.freq();
 
-    let mut hid: Box<dyn MouseInfoSender> = if SERIAL {
-        Box::new(CustomHID::new(
+    #[cfg(features = "serial")]
+    let mut hid = CustomHID::new(
         pac.USBCTRL_REGS,
         pac.USBCTRL_DPRAM,
         &mut pac.RESETS,
         clocks,
         10,
-        ))
-    } else {
-        Box::new(MouseHID::new(
+    );
+
+    #[cfg(not(features = "serial"))]
+    let mut hid = MouseHID::new(
         pac.USBCTRL_REGS,
         pac.USBCTRL_DPRAM,
         &mut pac.RESETS,
         core,
         clocks,
-        ))
-    };
+    );
 
     // The single-cycle I/O block controls our GPIO pins
     let sio = hal::Sio::new(pac.SIO);

src/serial.rs

@@ -27,15 +27,19 @@ impl<'a> Serial<'a> {
     pub fn send_number<T>(&mut self, i: impl NumToA<T>, base: T) {
         let s = i.numtoa_str(base, &mut self.buf);
 
-        self.send_text(s);
+        Self::send(&mut self.serial, s);
     }
 
     pub fn send_text(&mut self, s: &str) {
+        Self::send(&mut self.serial, s);
+    }
+
+    fn send(serial: &mut SerialPort<'a, UsbBus>, s: &str) {
         // Send back to the host
         let mut wr_ptr = s.as_bytes();
 
         while !wr_ptr.is_empty() {
-            match self.serial.write(wr_ptr) {
+            match serial.write(wr_ptr) {
                 Ok(len) => wr_ptr = &wr_ptr[len..],
                 // On error, just drop unwritten data.
                 // One possible error is Err(WouldBlock), meaning the USB