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/riscv-pac/src/lib.rs

@@ -0,0 +1,289 @@
+#![no_std]
+
+pub mod result;
+
+use result::Result;
+
+/// Trait for enums of target-specific exception numbers.
+///
+/// This trait should be implemented by a peripheral access crate (PAC) on its enum of available
+/// exceptions for a specific device. Alternatively, the `riscv` crate provides a default
+/// implementation for the RISC-V ISA. Each variant must convert to a `usize` of its exception number.
+///
+/// # Safety
+///
+/// * This trait must only be implemented on the `riscv` crate or on a PAC of a RISC-V target.
+/// * This trait must only be implemented on enums of exceptions.
+/// * Each enum variant must represent a distinct value (no duplicates are permitted),
+/// * Each enum variant must always return the same value (do not change at runtime).
+/// * All the exception numbers must be less than or equal to `MAX_EXCEPTION_NUMBER`.
+/// * `MAX_EXCEPTION_NUMBER` must coincide with the highest allowed exception number.
+pub unsafe trait ExceptionNumber: Copy {
+    /// Highest number assigned to an exception.
+    const MAX_EXCEPTION_NUMBER: usize;
+
+    /// Converts an exception to its corresponding number.
+    fn number(self) -> usize;
+
+    /// Tries to convert a number to a valid exception.
+    fn from_number(value: usize) -> Result<Self>;
+}
+
+/// Trait for enums of target-specific interrupt numbers.
+///
+/// This trait should be implemented by a peripheral access crate (PAC) on its enum of available
+/// interrupts for a specific device. Alternatively, the `riscv` crate provides a default
+/// implementation for the RISC-V ISA. Each variant must convert to a `usize` of its interrupt number.
+///
+/// # Safety
+///
+/// * This trait must only be implemented on the `riscv` crate or on a PAC of a RISC-V target.
+/// * This trait must only be implemented on enums of interrupts.
+/// * Each enum variant must represent a distinct value (no duplicates are permitted),
+/// * Each enum variant must always return the same value (do not change at runtime).
+/// * All the interrupt numbers must be less than or equal to `MAX_INTERRUPT_NUMBER`.
+/// * `MAX_INTERRUPT_NUMBER` must coincide with the highest allowed interrupt number.
+pub unsafe trait InterruptNumber: Copy {
+    /// Highest number assigned to an interrupt source.
+    const MAX_INTERRUPT_NUMBER: usize;
+
+    /// Converts an interrupt source to its corresponding number.
+    fn number(self) -> usize;
+
+    /// Tries to convert a number to a valid interrupt.
+    fn from_number(value: usize) -> Result<Self>;
+}
+
+/// Marker trait for enums of target-specific core interrupt numbers.
+///
+/// Core interrupts are interrupts are retrieved from the `mcause` CSR. Usually, vectored mode is
+/// only available for core interrupts. The `riscv` crate provides a default implementation for
+/// the RISC-V ISA. However, a PAC may override the default implementation if the target has a
+/// different interrupt numbering scheme (e.g., ESP32C3).
+///
+/// # Safety
+///
+/// Each enum variant must represent a valid core interrupt number read from the `mcause` CSR.
+pub unsafe trait CoreInterruptNumber: InterruptNumber {}
+
+/// Marker trait for enums of target-specific external interrupt numbers.
+///
+/// External interrupts are interrupts caused by external sources (e.g., GPIO, UART, SPI).
+/// External interrupts are **not** retrieved from the `mcause` CSR.
+/// Instead, RISC-V processors have a single core interrupt for all external interrupts.
+/// An additional peripheral (e.g., PLIC) is used to multiplex the external interrupts.
+///
+/// # Safety
+///
+/// Each enum variant must represent a valid external interrupt number.
+pub unsafe trait ExternalInterruptNumber: InterruptNumber {}
+
+/// Trait for enums of priority levels.
+///
+/// This trait should be implemented by a peripheral access crate (PAC) on its enum of available
+/// priority numbers for a specific device. Each variant must convert to a `usize` of its priority level.
+///
+/// # Safety
+///
+/// * This trait must only be implemented on a PAC of a RISC-V target.
+/// * This trait must only be implemented on enums of priority levels.
+/// * Each enum variant must represent a distinct value (no duplicates are permitted).
+/// * Each enum variant must always return the same value (do not change at runtime).
+/// * All the priority level numbers must be less than or equal to `MAX_PRIORITY_NUMBER`.
+/// * `MAX_PRIORITY_NUMBER` must coincide with the highest allowed priority number.
+pub unsafe trait PriorityNumber: Copy {
+    /// Number assigned to the highest priority level.
+    const MAX_PRIORITY_NUMBER: usize;
+
+    /// Converts a priority level to its corresponding number.
+    fn number(self) -> usize;
+
+    /// Tries to convert a number to a valid priority level.
+    fn from_number(value: usize) -> Result<Self>;
+}
+
+/// Trait for enums of HART identifiers.
+///
+/// This trait should be implemented by a peripheral access crate (PAC) on its enum of available
+/// HARTs for a specific device. Each variant must convert to a `usize` of its HART ID number.
+///
+/// # Safety
+///
+/// * This trait must only be implemented on a PAC of a RISC-V target.
+/// * This trait must only be implemented on enums of HART IDs.
+/// * Each enum variant must represent a distinct value (no duplicates are permitted),
+/// * Each anum variant must always return the same value (do not change at runtime).
+/// * All the HART ID numbers must be less than or equal to `MAX_HART_ID_NUMBER`.
+/// * `MAX_HART_ID_NUMBER` must coincide with the highest allowed HART ID number.
+pub unsafe trait HartIdNumber: Copy {
+    /// Highest number assigned to a context.
+    const MAX_HART_ID_NUMBER: usize;
+
+    /// Converts a HART ID to its corresponding number.
+    fn number(self) -> usize;
+
+    /// Tries to convert a number to a valid HART ID.
+    fn from_number(value: usize) -> Result<Self>;
+}
+
+#[cfg(test)]
+mod test {
+    use super::*;
+    use crate::result::Error;
+
+    #[derive(Clone, Copy, Debug, Eq, PartialEq)]
+    enum Exception {
+        E1 = 1,
+        E3 = 3,
+    }
+
+    #[derive(Clone, Copy, Debug, Eq, PartialEq)]
+    enum Interrupt {
+        I1 = 1,
+        I2 = 2,
+        I4 = 4,
+    }
+
+    #[derive(Clone, Copy, Debug, Eq, PartialEq)]
+    enum Priority {
+        P0 = 0,
+        P1 = 1,
+        P2 = 2,
+        P3 = 3,
+    }
+
+    #[derive(Clone, Copy, Debug, Eq, PartialEq)]
+    enum HartId {
+        H0 = 0,
+        H1 = 1,
+        H2 = 2,
+    }
+
+    unsafe impl ExceptionNumber for Exception {
+        const MAX_EXCEPTION_NUMBER: usize = Self::E3 as usize;
+
+        #[inline]
+        fn number(self) -> usize {
+            self as _
+        }
+
+        #[inline]
+        fn from_number(number: usize) -> Result<Self> {
+            match number {
+                1 => Ok(Exception::E1),
+                3 => Ok(Exception::E3),
+                _ => Err(Error::InvalidVariant(number)),
+            }
+        }
+    }
+
+    unsafe impl InterruptNumber for Interrupt {
+        const MAX_INTERRUPT_NUMBER: usize = Self::I4 as usize;
+
+        #[inline]
+        fn number(self) -> usize {
+            self as _
+        }
+
+        #[inline]
+        fn from_number(number: usize) -> Result<Self> {
+            match number {
+                1 => Ok(Interrupt::I1),
+                2 => Ok(Interrupt::I2),
+                4 => Ok(Interrupt::I4),
+                _ => Err(Error::InvalidVariant(number)),
+            }
+        }
+    }
+
+    unsafe impl PriorityNumber for Priority {
+        const MAX_PRIORITY_NUMBER: usize = Self::P3 as usize;
+
+        #[inline]
+        fn number(self) -> usize {
+            self as _
+        }
+
+        #[inline]
+        fn from_number(number: usize) -> Result<Self> {
+            match number {
+                0 => Ok(Priority::P0),
+                1 => Ok(Priority::P1),
+                2 => Ok(Priority::P2),
+                3 => Ok(Priority::P3),
+                _ => Err(Error::InvalidVariant(number)),
+            }
+        }
+    }
+
+    unsafe impl HartIdNumber for HartId {
+        const MAX_HART_ID_NUMBER: usize = Self::H2 as usize;
+
+        #[inline]
+        fn number(self) -> usize {
+            self as _
+        }
+
+        #[inline]
+        fn from_number(number: usize) -> Result<Self> {
+            match number {
+                0 => Ok(HartId::H0),
+                1 => Ok(HartId::H1),
+                2 => Ok(HartId::H2),
+                _ => Err(Error::InvalidVariant(number)),
+            }
+        }
+    }
+
+    #[test]
+    fn check_exception_enum() {
+        assert_eq!(Exception::E1.number(), 1);
+        assert_eq!(Exception::E3.number(), 3);
+
+        assert_eq!(Exception::from_number(0), Err(Error::InvalidVariant(0)));
+        assert_eq!(Exception::from_number(1), Ok(Exception::E1));
+        assert_eq!(Exception::from_number(2), Err(Error::InvalidVariant(2)));
+        assert_eq!(Exception::from_number(3), Ok(Exception::E3));
+        assert_eq!(Exception::from_number(4), Err(Error::InvalidVariant(4)));
+    }
+
+    #[test]
+    fn check_interrupt_enum() {
+        assert_eq!(Interrupt::I1.number(), 1);
+        assert_eq!(Interrupt::I2.number(), 2);
+        assert_eq!(Interrupt::I4.number(), 4);
+
+        assert_eq!(Interrupt::from_number(0), Err(Error::InvalidVariant(0)));
+        assert_eq!(Interrupt::from_number(1), Ok(Interrupt::I1));
+        assert_eq!(Interrupt::from_number(2), Ok(Interrupt::I2));
+        assert_eq!(Interrupt::from_number(3), Err(Error::InvalidVariant(3)));
+        assert_eq!(Interrupt::from_number(4), Ok(Interrupt::I4));
+        assert_eq!(Interrupt::from_number(5), Err(Error::InvalidVariant(5)));
+    }
+
+    #[test]
+    fn check_priority_enum() {
+        assert_eq!(Priority::P0.number(), 0);
+        assert_eq!(Priority::P1.number(), 1);
+        assert_eq!(Priority::P2.number(), 2);
+        assert_eq!(Priority::P3.number(), 3);
+
+        assert_eq!(Priority::from_number(0), Ok(Priority::P0));
+        assert_eq!(Priority::from_number(1), Ok(Priority::P1));
+        assert_eq!(Priority::from_number(2), Ok(Priority::P2));
+        assert_eq!(Priority::from_number(3), Ok(Priority::P3));
+        assert_eq!(Priority::from_number(4), Err(Error::InvalidVariant(4)));
+    }
+
+    #[test]
+    fn check_hart_id_enum() {
+        assert_eq!(HartId::H0.number(), 0);
+        assert_eq!(HartId::H1.number(), 1);
+        assert_eq!(HartId::H2.number(), 2);
+
+        assert_eq!(HartId::from_number(0), Ok(HartId::H0));
+        assert_eq!(HartId::from_number(1), Ok(HartId::H1));
+        assert_eq!(HartId::from_number(2), Ok(HartId::H2));
+        assert_eq!(HartId::from_number(3), Err(Error::InvalidVariant(3)));
+    }
+}

vendor/riscv-pac/src/result.rs

@@ -0,0 +1,58 @@
+use core::fmt;
+
+/// Convenience alias for the [Result](core::result::Result) type for the library.
+pub type Result<T> = core::result::Result<T, Error>;
+
+/// Represents error variants for the library.
+#[derive(Clone, Copy, Debug, Eq, PartialEq)]
+pub enum Error {
+    /// Attempted out-of-bounds access.
+    IndexOutOfBounds {
+        index: usize,
+        min: usize,
+        max: usize,
+    },
+    /// Invalid field value.
+    InvalidFieldValue {
+        field: &'static str,
+        value: usize,
+        bitmask: usize,
+    },
+    /// Invalid value of a register field that does not match any known variants.
+    InvalidFieldVariant { field: &'static str, value: usize },
+    /// Invalid value.
+    InvalidValue { value: usize, bitmask: usize },
+    /// Invalid value that does not match any known variants.
+    InvalidVariant(usize),
+    /// Unimplemented function or type.
+    Unimplemented,
+}
+
+impl fmt::Display for Error {
+    fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
+        match self {
+            Self::IndexOutOfBounds { index, min, max } => write!(
+                f,
+                "out-of-bounds access, index: {index}, min: {min}, max: {max}"
+            ),
+            Self::InvalidFieldValue {
+                field,
+                value,
+                bitmask,
+            } => write!(
+                f,
+                "invalid {field} field value: {value:#x}, valid bitmask: {bitmask:#x}",
+            ),
+            Self::InvalidFieldVariant { field, value } => {
+                write!(f, "invalid {field} field variant: {value:#x}")
+            }
+            Self::InvalidValue { value, bitmask } => {
+                write!(f, "invalid value: {value:#x}, valid bitmask: {bitmask:#x}",)
+            }
+            Self::InvalidVariant(value) => {
+                write!(f, "invalid variant: {value:#x}")
+            }
+            Self::Unimplemented => write!(f, "unimplemented"),
+        }
+    }
+}