4 files changed, 263 insertions, 17 deletions

diff --git a/ble/src/logger.rs b/ble/src/logger.rs
new file mode 100644
index 0000000..f102b74
--- /dev/null
+++ b/ble/src/logger.rs
@@ -0,0 +1,127 @@
+use crate::rtc;
+
+use core::cell::UnsafeCell;
+use core::fmt::{self, Write};
+use log::{Metadata, Record};
+use nrf52840_hal::{target::UARTE0, uarte, Uarte};
+use starb::{Reader, RingBuffer, Writer};
+
+static mut UARTE0: usize = 0;
+
+struct JoinedRingBuffer<'a> {
+    lbr: Reader<'a, u8>,
+    lbw: Writer<'a, u8>,
+}
+
+impl<'a> JoinedRingBuffer<'a> {
+    const fn new(rb: &'a RingBuffer<u8>) -> Self {
+        let (lbr, lbw) = rb.split();
+        Self { lbr: lbr, lbw: lbw }
+    }
+}
+
+impl fmt::Write for JoinedRingBuffer<'_> {
+    fn write_str(&mut self, s: &str) -> Result<(), fmt::Error> {
+        for b in s.bytes() {
+            if let Err(_) = self.lbw.unshift(b) {
+                // Ignore buffer full errors for logging.
+                return Ok(());
+            }
+        }
+        Ok(())
+    }
+}
+
+static mut LB: RingBuffer<u8> = RingBuffer::<u8>::new(0);
+static mut JRB: JoinedRingBuffer = unsafe { JoinedRingBuffer::new(&LB) };
+
+// The UART isn't necessarily Sync, so wrap it in something that
+// is. As long as flush() is only called from one thread, we're fine,
+// but this is a guarantee that the logger module doesn't make.
+pub struct WriteWrapper<W> {
+    w: W,
+}
+impl<W> WriteWrapper<W> {
+    pub fn new(writer: W) -> Self {
+        Self { w: writer }
+    }
+}
+unsafe impl<W> Sync for WriteWrapper<W> {}
+
+pub struct SerialLogger<W> {
+    writer: UnsafeCell<WriteWrapper<Uarte<W>>>,
+}
+
+impl<W> SerialLogger<W>
+where
+    W: uarte::Instance,
+{
+    pub fn new(writer: WriteWrapper<Uarte<W>>) -> Self {
+        // Stash this for unsafe usage in case there's an issue with
+        // the rest of the logging.
+        unsafe { UARTE0 = core::mem::transmute(&writer.w) };
+        Self {
+            writer: UnsafeCell::new(writer),
+        }
+    }
+}
+unsafe impl<W> Send for SerialLogger<W> {}
+unsafe impl<W> Sync for SerialLogger<W> {}
+
+impl<W> log::Log for SerialLogger<W>
+where
+    W: uarte::Instance,
+{
+    fn enabled(&self, metadata: &Metadata) -> bool {
+        metadata.level() <= log::max_level()
+    }
+
+    fn log(&self, record: &Record) {
+        if !self.enabled(record.metadata()) {
+            return;
+        }
+
+        let jrb = unsafe { &mut JRB };
+        write!(
+            jrb,
+            "[{}] {} {} -- {}\r\n",
+            rtc::millis(),
+            record.level(),
+            record.target(),
+            record.args()
+        )
+        .ok();
+    }
+
+    fn flush(&self) {
+        // Unsafe due to mutable static. We can only deal with the
+        // tail position of the buffer here to keep things safe.
+        let jrb = unsafe { &mut JRB };
+        if jrb.lbr.is_empty() {
+            return;
+        }
+
+        let writer = unsafe { &mut (*self.writer.get()) };
+        while let Some(b) = jrb.lbr.shift() {
+            // TODO: The UARTE peripheral uses DMA to send a bunch of
+            // stuff at speed, in hardware. It would be nice to use
+            // it, but we can't just take a slice of the ring buffer,
+            // since we don't know about its internal structure here.
+            writer.w.write(&[b]).expect("writing log");
+        }
+    }
+}
+
+// Write to the UART right now, instead of putting it on a ring
+// buffer. This function is a huge hack, and only useful for debugging
+// either before the main loop starts or if the ring buffer is broken.
+pub unsafe fn write_fmt_now(args: fmt::Arguments, nl: bool) {
+    if UARTE0 == 0 {
+        return;
+    }
+    let uart: &mut Uarte<UARTE0> = core::mem::transmute(UARTE0);
+    fmt::write(uart, args).expect("writing fmt now to uart");
+    if nl {
+        uart.write_str("\r\n").expect("writing nl now to uart");
+    }
+}
diff --git a/ble/src/macros.rs b/ble/src/macros.rs
new file mode 100644
index 0000000..46d2d07
--- /dev/null
+++ b/ble/src/macros.rs
@@ -0,0 +1,15 @@
+#[macro_export]
+macro_rules! logln_now {
+    ($($arg:tt)*) => {
+        unsafe {crate::logger::write_fmt_now(format_args!($($arg)*), true);}
+    };
+    (_) => {};
+}
+
+#[macro_export]
+macro_rules! log_now {
+    ($($arg:tt)*) => {
+        unsafe {crate::logger::write_fmt_now(format_args!($($arg)*), false);}
+    };
+    (_) => {};
+}
diff --git a/ble/src/main.rs b/ble/src/main.rs
index 8b8c513..6f167a5 100644
--- a/ble/src/main.rs
+++ b/ble/src/main.rs
@@ -1,39 +1,75 @@
 //! BLE interface.
+
 #![no_std]
 #![no_main]
 
-use core::fmt::Write;
+mod logger;
+mod macros;
+mod rtc;
+
+use clint::HandlerArray;
+use core::mem;
+use cortex_m::asm::wfi;
 use cortex_m_rt::entry;
-use nb::block;
+use log::{info, trace, LevelFilter};
 
 #[allow(unused_imports)]
 extern crate panic_semihosting;
 
 use nrf52840_mdk_bsp::{
     hal::{
-        prelude::*,
-        timer::{self, Timer},
+        target::{interrupt, Interrupt, UARTE0},
+        Clocks, Rtc,
     },
     Board,
 };
 
+// TODO:
+//   * set up serial reader for trinket
+//   * set up i²c interface for keyboard reports
+//   * and, finally, bluetooth
+
+// Interrupt handler table.
+static HANDLERS: HandlerArray = HandlerArray::new();
+
 #[entry]
 fn main() -> ! {
-    let mut nrf52 = Board::take().unwrap();
+    let nrf52 = Board::take().unwrap();
+
+    let uart_wrapped = logger::WriteWrapper::new(nrf52.cdc);
+    let logger = logger::SerialLogger::new(uart_wrapped);
+    let logger_ref: &'static logger::SerialLogger<UARTE0> = unsafe { mem::transmute(&logger) };
+    log::set_logger(logger_ref).expect("setting logger");
+    log::set_max_level(LevelFilter::Trace);
+
+    nrf52.RTC0.intenset.write(|w| w.tick().set());
+
+    let mut nvic = nrf52.NVIC;
+    let mut rtc_handler = rtc::setup(Rtc::new(nrf52.RTC0), Clocks::new(nrf52.CLOCK));
 
-    let mut timer = Timer::new(nrf52.TIMER0);
+    logln_now!("logln_now?");
+    HANDLERS.with_overrides(|hs| {
+        hs.register(0, &mut rtc_handler);
+        nvic.enable(Interrupt::RTC0);
 
-    write!(nrf52.cdc, "Bootstrap complete.").ok();
-    loop {
-        write!(nrf52.cdc, ".").ok();
-        delay(&mut timer, 1_000_000); // 1s
-    }
+        info!("Bootstrap complete.");
+        let mut last_tick = rtc::millis();
+        last_tick -= last_tick % 1024;
+        loop {
+            let tick = rtc::millis();
+            if tick >= last_tick + 1024 {
+                last_tick = tick;
+                last_tick -= last_tick % 1024;
+                trace!(".");
+            }
+            wfi();
+        }
+    });
+    unreachable!();
 }
 
-fn delay<T>(timer: &mut Timer<T>, cycles: u32)
-where
-    T: timer::Instance,
-{
-    timer.start(cycles);
-    let _ = block!(timer.wait());
+// TODO: RTC0/1/2 exist. See which is best, if it matters.
+#[interrupt]
+fn RTC0() {
+    HANDLERS.call(0);
 }
diff --git a/ble/src/rtc.rs b/ble/src/rtc.rs
new file mode 100644
index 0000000..8fe581f
--- /dev/null
+++ b/ble/src/rtc.rs
@@ -0,0 +1,68 @@
+use core::sync::atomic::{AtomicUsize, Ordering};
+use log::trace;
+use nrf52840_hal::{
+    clocks::LfOscStopped,
+    rtc::{self, RtcInterrupt},
+    Clocks, Rtc,
+};
+
+struct MilliClock(AtomicUsize);
+impl MilliClock {
+    const fn new() -> Self {
+        Self(AtomicUsize::new(0))
+    }
+
+    #[allow(unused)]
+    fn set(&self, millis: usize) {
+        self.0.store(millis, Ordering::SeqCst)
+    }
+
+    #[allow(unused)]
+    fn add(&self, val: usize) -> usize {
+        self.0.fetch_add(val, Ordering::SeqCst)
+    }
+
+    // Slightly less than 1ms, due to using a 32,768Hz clock, we can't
+    // hit exactly 1ms, so we shoot for a bit under.
+    fn millis(&self) -> usize {
+        self.0.load(Ordering::SeqCst)
+    }
+}
+
+static CLOCK: MilliClock = MilliClock::new();
+
+pub fn setup<R, H, L>(
+    mut rtc: Rtc<R, rtc::Stopped>,
+    clock: Clocks<H, L, LfOscStopped>,
+) -> impl FnMut()
+where
+    R: rtc::Instance,
+{
+    trace!("setting up clock");
+
+    clock.set_lfclk_src_rc().start_lfclk();
+
+    // Try to set clock to 1kHz.
+    match rtc.set_prescaler(32) {
+        Ok(()) => trace!("set prescaler!"),
+        Err(x) => trace!("couldn't set prescaler: {:?}", x),
+    }
+    // Make sure event is cleared before start.
+    let _ = rtc.get_event_triggered(RtcInterrupt::Tick, true);
+
+    let mut rtc = rtc.enable_counter();
+    move || handler(&mut rtc)
+}
+
+pub fn millis() -> usize {
+    CLOCK.millis()
+}
+
+fn handler<R>(rtc: &mut Rtc<R, rtc::Started>)
+where
+    R: rtc::Instance,
+{
+    let _ = rtc.get_event_triggered(RtcInterrupt::Tick, true);
+    CLOCK.add(1);
+    log::logger().flush();
+}