feat: add display UI with splash screen, dashboard, and RSSI sparkline

Implement full SSD1306 OLED display support:
- Splash screen on boot (1.5s) with project name, version, board
- Dashboard showing radio state, config, counters, RSSI/SNR
- RSSI history sparkline (64-sample ring buffer, 2px-wide bars)
- DisplayOn/DisplayOff host commands routed via dedicated channel
- Pure render functions against generic DrawTarget (no hardware coupling)
- Display on/off control bypasses radio task entirely

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

vendor/bytemuck/tests/cast_slice_tests.rs

@@ -0,0 +1,371 @@
+#![allow(clippy::unnecessary_cast)]
+#![allow(clippy::manual_slice_size_calculation)]
+
+use core::mem::size_of;
+
+use bytemuck::*;
+
+#[test]
+fn test_try_cast_slice() {
+  // some align4 data
+  let u32_slice: &[u32] = &[4, 5, 6];
+  // the same data as align1
+  let the_bytes: &[u8] = try_cast_slice(u32_slice).unwrap();
+
+  assert_eq!(
+    u32_slice.as_ptr() as *const u32 as usize,
+    the_bytes.as_ptr() as *const u8 as usize
+  );
+  assert_eq!(
+    u32_slice.len() * size_of::<u32>(),
+    the_bytes.len() * size_of::<u8>()
+  );
+
+  // by taking one byte off the front, we're definitely mis-aligned for u32.
+  let mis_aligned_bytes = &the_bytes[1..];
+  assert_eq!(
+    try_cast_slice::<u8, u32>(mis_aligned_bytes),
+    Err(PodCastError::TargetAlignmentGreaterAndInputNotAligned)
+  );
+
+  // by taking one byte off the end, we're aligned but would have slop bytes for
+  // u32
+  let the_bytes_len_minus1 = the_bytes.len() - 1;
+  let slop_bytes = &the_bytes[..the_bytes_len_minus1];
+  assert_eq!(
+    try_cast_slice::<u8, u32>(slop_bytes),
+    Err(PodCastError::OutputSliceWouldHaveSlop)
+  );
+
+  // if we don't mess with it we can up-alignment cast
+  try_cast_slice::<u8, u32>(the_bytes).unwrap();
+}
+
+#[test]
+fn test_try_cast_slice_mut() {
+  // some align4 data
+  let u32_slice: &mut [u32] = &mut [4, 5, 6];
+  let u32_len = u32_slice.len();
+  let u32_ptr = u32_slice.as_ptr();
+
+  // the same data as align1
+  let the_bytes: &mut [u8] = try_cast_slice_mut(u32_slice).unwrap();
+  let the_bytes_len = the_bytes.len();
+  let the_bytes_ptr = the_bytes.as_ptr();
+
+  assert_eq!(
+    u32_ptr as *const u32 as usize,
+    the_bytes_ptr as *const u8 as usize
+  );
+  assert_eq!(u32_len * size_of::<u32>(), the_bytes_len * size_of::<u8>());
+
+  // by taking one byte off the front, we're definitely mis-aligned for u32.
+  let mis_aligned_bytes = &mut the_bytes[1..];
+  assert_eq!(
+    try_cast_slice_mut::<u8, u32>(mis_aligned_bytes),
+    Err(PodCastError::TargetAlignmentGreaterAndInputNotAligned)
+  );
+
+  // by taking one byte off the end, we're aligned but would have slop bytes for
+  // u32
+  let the_bytes_len_minus1 = the_bytes.len() - 1;
+  let slop_bytes = &mut the_bytes[..the_bytes_len_minus1];
+  assert_eq!(
+    try_cast_slice_mut::<u8, u32>(slop_bytes),
+    Err(PodCastError::OutputSliceWouldHaveSlop)
+  );
+
+  // if we don't mess with it we can up-alignment cast
+  try_cast_slice_mut::<u8, u32>(the_bytes).unwrap();
+}
+
+#[test]
+fn test_types() {
+  let _: i32 = cast(1.0_f32);
+  let _: &mut i32 = cast_mut(&mut 1.0_f32);
+  let _: &i32 = cast_ref(&1.0_f32);
+  let _: &[i32] = cast_slice(&[1.0_f32]);
+  let _: &mut [i32] = cast_slice_mut(&mut [1.0_f32]);
+  //
+  let _: Result<i32, PodCastError> = try_cast(1.0_f32);
+  let _: Result<&mut i32, PodCastError> = try_cast_mut(&mut 1.0_f32);
+  let _: Result<&i32, PodCastError> = try_cast_ref(&1.0_f32);
+  let _: Result<&[i32], PodCastError> = try_cast_slice(&[1.0_f32]);
+  let _: Result<&mut [i32], PodCastError> = try_cast_slice_mut(&mut [1.0_f32]);
+}
+
+#[test]
+fn test_bytes_of() {
+  assert_eq!(bytes_of(&0xaabbccdd_u32), &0xaabbccdd_u32.to_ne_bytes());
+  assert_eq!(
+    bytes_of_mut(&mut 0xaabbccdd_u32),
+    &mut 0xaabbccdd_u32.to_ne_bytes()
+  );
+  let mut a = 0xaabbccdd_u32;
+  let a_addr = &a as *const _ as usize;
+  // ensure addresses match.
+  assert_eq!(bytes_of(&a).as_ptr() as usize, a_addr);
+  assert_eq!(bytes_of_mut(&mut a).as_ptr() as usize, a_addr);
+}
+
+#[test]
+fn test_try_from_bytes() {
+  let u32s = [0xaabbccdd, 0x11223344_u32];
+  let bytes = bytemuck::cast_slice::<u32, u8>(&u32s);
+  assert_eq!(try_from_bytes::<u32>(&bytes[..4]), Ok(&u32s[0]));
+  assert_eq!(
+    try_from_bytes::<u32>(&bytes[..5]),
+    Err(PodCastError::SizeMismatch)
+  );
+  assert_eq!(
+    try_from_bytes::<u32>(&bytes[..3]),
+    Err(PodCastError::SizeMismatch)
+  );
+  assert_eq!(
+    try_from_bytes::<u32>(&bytes[1..5]),
+    Err(PodCastError::TargetAlignmentGreaterAndInputNotAligned)
+  );
+}
+
+#[test]
+fn test_try_from_bytes_mut() {
+  let mut abcd = 0xaabbccdd;
+  let mut u32s = [abcd, 0x11223344_u32];
+  let bytes = bytemuck::cast_slice_mut::<u32, u8>(&mut u32s);
+  assert_eq!(try_from_bytes_mut::<u32>(&mut bytes[..4]), Ok(&mut abcd));
+  assert_eq!(try_from_bytes_mut::<u32>(&mut bytes[..4]), Ok(&mut abcd));
+  assert_eq!(
+    try_from_bytes_mut::<u32>(&mut bytes[..5]),
+    Err(PodCastError::SizeMismatch)
+  );
+  assert_eq!(
+    try_from_bytes_mut::<u32>(&mut bytes[..3]),
+    Err(PodCastError::SizeMismatch)
+  );
+  assert_eq!(
+    try_from_bytes::<u32>(&bytes[1..5]),
+    Err(PodCastError::TargetAlignmentGreaterAndInputNotAligned)
+  );
+}
+
+#[test]
+fn test_from_bytes() {
+  let abcd = 0xaabbccdd_u32;
+  let aligned_bytes = bytemuck::bytes_of(&abcd);
+  assert_eq!(from_bytes::<u32>(aligned_bytes), &abcd);
+  assert!(core::ptr::eq(from_bytes(aligned_bytes), &abcd));
+}
+
+#[test]
+fn test_from_bytes_mut() {
+  let mut a = 0xaabbccdd_u32;
+  let a_addr = &a as *const _ as usize;
+  let aligned_bytes = bytemuck::bytes_of_mut(&mut a);
+  assert_eq!(*from_bytes_mut::<u32>(aligned_bytes), 0xaabbccdd_u32);
+  assert_eq!(
+    from_bytes_mut::<u32>(aligned_bytes) as *const u32 as usize,
+    a_addr
+  );
+}
+
+// like #[should_panic], but can be a part of another test, instead of requiring
+// it to be it's own test.
+macro_rules! should_panic {
+  ($ex:expr) => {
+    assert!(
+      std::panic::catch_unwind(|| {
+        let _ = $ex;
+      })
+      .is_err(),
+      concat!("should have panicked: `", stringify!($ex), "`")
+    );
+  };
+}
+
+#[test]
+fn test_panics() {
+  should_panic!(cast_slice::<u8, u32>(&[1u8, 2u8]));
+  should_panic!(cast_slice_mut::<u8, u32>(&mut [1u8, 2u8]));
+  should_panic!(from_bytes::<u32>(&[1u8, 2]));
+  should_panic!(from_bytes::<u32>(&[1u8, 2, 3, 4, 5]));
+  should_panic!(from_bytes_mut::<u32>(&mut [1u8, 2]));
+  should_panic!(from_bytes_mut::<u32>(&mut [1u8, 2, 3, 4, 5]));
+  // use cast_slice on some u32s to get some align>=4 bytes, so we can know
+  // we'll give from_bytes unaligned ones.
+  let aligned_bytes = bytemuck::cast_slice::<u32, u8>(&[0, 0]);
+  should_panic!(from_bytes::<u32>(&aligned_bytes[1..5]));
+}
+
+#[test]
+fn test_zsts() {
+  #[derive(Debug, Clone, Copy)]
+  struct MyZst;
+  unsafe impl Zeroable for MyZst {}
+  unsafe impl Pod for MyZst {}
+  assert_eq!(42, cast_slice::<(), MyZst>(&[(); 42]).len());
+  assert_eq!(42, cast_slice_mut::<(), MyZst>(&mut [(); 42]).len());
+  assert_eq!(0, cast_slice::<(), u8>(&[(); 42]).len());
+  assert_eq!(0, cast_slice_mut::<(), u8>(&mut [(); 42]).len());
+  assert_eq!(0, cast_slice::<u8, ()>(&[]).len());
+  assert_eq!(0, cast_slice_mut::<u8, ()>(&mut []).len());
+
+  assert_eq!(
+    PodCastError::OutputSliceWouldHaveSlop,
+    try_cast_slice::<u8, ()>(&[42]).unwrap_err()
+  );
+
+  assert_eq!(
+    PodCastError::OutputSliceWouldHaveSlop,
+    try_cast_slice_mut::<u8, ()>(&mut [42]).unwrap_err()
+  );
+}
+
+#[cfg(feature = "extern_crate_alloc")]
+#[test]
+fn test_boxed_slices() {
+  let boxed_u8_slice: Box<[u8]> = Box::new([0, 1, u8::MAX, i8::MAX as u8]);
+  let boxed_i8_slice: Box<[i8]> = cast_slice_box::<u8, i8>(boxed_u8_slice);
+  assert_eq!(&*boxed_i8_slice, [0, 1, -1, i8::MAX]);
+
+  let result: Result<Box<[u16]>, (PodCastError, Box<[i8]>)> =
+    try_cast_slice_box(boxed_i8_slice);
+  let (error, boxed_i8_slice) =
+    result.expect_err("u16 and i8 have different alignment");
+  assert_eq!(error, PodCastError::AlignmentMismatch);
+
+  let result: Result<&[[i8; 3]], PodCastError> =
+    try_cast_slice(&*boxed_i8_slice);
+  let error =
+    result.expect_err("slice of [i8; 3] cannot be made from slice of 4 i8s");
+  assert_eq!(error, PodCastError::OutputSliceWouldHaveSlop);
+
+  let result: Result<Box<[[i8; 3]]>, (PodCastError, Box<[i8]>)> =
+    try_cast_slice_box(boxed_i8_slice);
+  let (error, boxed_i8_slice) =
+    result.expect_err("slice of [i8; 3] cannot be made from slice of 4 i8s");
+  assert_eq!(error, PodCastError::OutputSliceWouldHaveSlop);
+
+  let empty: Box<[()]> = cast_slice_box::<u8, ()>(Box::new([]));
+  assert!(empty.is_empty());
+
+  let result: Result<Box<[()]>, (PodCastError, Box<[i8]>)> =
+    try_cast_slice_box(boxed_i8_slice);
+  let (error, boxed_i8_slice) =
+    result.expect_err("slice of ZST cannot be made from slice of 4 u8s");
+  assert_eq!(error, PodCastError::OutputSliceWouldHaveSlop);
+
+  drop(boxed_i8_slice);
+
+  let empty: Box<[i8]> = cast_slice_box::<(), i8>(Box::new([]));
+  assert!(empty.is_empty());
+
+  let empty: Box<[i8]> = cast_slice_box::<(), i8>(Box::new([(); 42]));
+  assert!(empty.is_empty());
+}
+
+#[cfg(feature = "extern_crate_alloc")]
+#[test]
+fn test_rc_slices() {
+  use std::rc::Rc;
+  let rc_u8_slice: Rc<[u8]> = Rc::new([0, 1, u8::MAX, i8::MAX as u8]);
+  let rc_i8_slice: Rc<[i8]> = cast_slice_rc::<u8, i8>(rc_u8_slice);
+  assert_eq!(&*rc_i8_slice, [0, 1, -1, i8::MAX]);
+
+  let result: Result<Rc<[u16]>, (PodCastError, Rc<[i8]>)> =
+    try_cast_slice_rc(rc_i8_slice);
+  let (error, rc_i8_slice) =
+    result.expect_err("u16 and i8 have different alignment");
+  assert_eq!(error, PodCastError::AlignmentMismatch);
+
+  let result: Result<&[[i8; 3]], PodCastError> = try_cast_slice(&*rc_i8_slice);
+  let error =
+    result.expect_err("slice of [i8; 3] cannot be made from slice of 4 i8s");
+  assert_eq!(error, PodCastError::OutputSliceWouldHaveSlop);
+
+  let result: Result<Rc<[[i8; 3]]>, (PodCastError, Rc<[i8]>)> =
+    try_cast_slice_rc(rc_i8_slice);
+  let (error, rc_i8_slice) =
+    result.expect_err("slice of [i8; 3] cannot be made from slice of 4 i8s");
+  assert_eq!(error, PodCastError::OutputSliceWouldHaveSlop);
+
+  let empty: Rc<[()]> = cast_slice_rc::<u8, ()>(Rc::new([]));
+  assert!(empty.is_empty());
+
+  let result: Result<Rc<[()]>, (PodCastError, Rc<[i8]>)> =
+    try_cast_slice_rc(rc_i8_slice);
+  let (error, rc_i8_slice) =
+    result.expect_err("slice of ZST cannot be made from slice of 4 u8s");
+  assert_eq!(error, PodCastError::OutputSliceWouldHaveSlop);
+
+  drop(rc_i8_slice);
+
+  let empty: Rc<[i8]> = cast_slice_rc::<(), i8>(Rc::new([]));
+  assert!(empty.is_empty());
+
+  let empty: Rc<[i8]> = cast_slice_rc::<(), i8>(Rc::new([(); 42]));
+  assert!(empty.is_empty());
+}
+
+#[cfg(feature = "extern_crate_alloc")]
+#[cfg(target_has_atomic = "ptr")]
+#[test]
+fn test_arc_slices() {
+  use std::sync::Arc;
+  let arc_u8_slice: Arc<[u8]> = Arc::new([0, 1, u8::MAX, i8::MAX as u8]);
+  let arc_i8_slice: Arc<[i8]> = cast_slice_arc::<u8, i8>(arc_u8_slice);
+  assert_eq!(&*arc_i8_slice, [0, 1, -1, i8::MAX]);
+
+  let result: Result<Arc<[u16]>, (PodCastError, Arc<[i8]>)> =
+    try_cast_slice_arc(arc_i8_slice);
+  let (error, arc_i8_slice) =
+    result.expect_err("u16 and i8 have different alignment");
+  assert_eq!(error, PodCastError::AlignmentMismatch);
+
+  let result: Result<&[[i8; 3]], PodCastError> = try_cast_slice(&*arc_i8_slice);
+  let error =
+    result.expect_err("slice of [i8; 3] cannot be made from slice of 4 i8s");
+  assert_eq!(error, PodCastError::OutputSliceWouldHaveSlop);
+
+  let result: Result<Arc<[[i8; 3]]>, (PodCastError, Arc<[i8]>)> =
+    try_cast_slice_arc(arc_i8_slice);
+  let (error, arc_i8_slice) =
+    result.expect_err("slice of [i8; 3] cannot be made from slice of 4 i8s");
+  assert_eq!(error, PodCastError::OutputSliceWouldHaveSlop);
+
+  let empty: Arc<[()]> = cast_slice_arc::<u8, ()>(Arc::new([]));
+  assert!(empty.is_empty());
+
+  let result: Result<Arc<[()]>, (PodCastError, Arc<[i8]>)> =
+    try_cast_slice_arc(arc_i8_slice);
+  let (error, arc_i8_slice) =
+    result.expect_err("slice of ZST cannot be made from slice of 4 u8s");
+  assert_eq!(error, PodCastError::OutputSliceWouldHaveSlop);
+
+  drop(arc_i8_slice);
+
+  let empty: Arc<[i8]> = cast_slice_arc::<(), i8>(Arc::new([]));
+  assert!(empty.is_empty());
+
+  let empty: Arc<[i8]> = cast_slice_arc::<(), i8>(Arc::new([(); 42]));
+  assert!(empty.is_empty());
+}
+
+#[cfg(feature = "extern_crate_alloc")]
+#[test]
+fn box_bytes_zst() {
+  let x: BoxBytes = box_bytes_of(Box::new([0u8; 0]));
+  let _: Box<[u8]> = from_box_bytes(x);
+
+  let x: BoxBytes = box_bytes_of(Box::new([0u8; 0]));
+  let _: Box<[()]> = from_box_bytes(x);
+
+  let x: BoxBytes = box_bytes_of(Box::new([(); 0]));
+  let _: Box<[u8]> = from_box_bytes(x);
+
+  let x: BoxBytes = box_bytes_of(Box::new([0u8]));
+  let res: Result<Box<[()]>, _> = try_from_box_bytes(x);
+  assert_eq!(res.unwrap_err().0, PodCastError::OutputSliceWouldHaveSlop);
+
+  // regression test for dropping zero-sized BoxBytes
+  let _: BoxBytes = box_bytes_of(Box::new([0u8; 0]));
+}