From f7c3005345df07bad5c42612fd73974bd569affb Mon Sep 17 00:00:00 2001
From: Robin Mueller <robin.mueller.m@pm.me>
Date: Fri, 19 Sep 2025 17:38:24 +0200
Subject: add basic RTC driver for nRF

---
 examples/nrf52840/Cargo.toml     |  1 +
 examples/nrf52840/src/bin/rtc.rs | 57 ++++++++++++++++++++++++++++++++++++++++
 2 files changed, 58 insertions(+)
 create mode 100644 examples/nrf52840/src/bin/rtc.rs

(limited to 'examples')

diff --git a/examples/nrf52840/Cargo.toml b/examples/nrf52840/Cargo.toml
index 452e83b7e..ca3c6f863 100644
--- a/examples/nrf52840/Cargo.toml
+++ b/examples/nrf52840/Cargo.toml
@@ -35,6 +35,7 @@ embedded-hal-async = { version = "1.0" }
 embedded-hal-bus = { version = "0.1", features = ["async"] }
 num-integer = { version = "0.1.45", default-features = false }
 microfft = "0.5.0"
+portable-atomic = "1"
 
 [profile.release]
 debug = 2
diff --git a/examples/nrf52840/src/bin/rtc.rs b/examples/nrf52840/src/bin/rtc.rs
new file mode 100644
index 000000000..a3df7da14
--- /dev/null
+++ b/examples/nrf52840/src/bin/rtc.rs
@@ -0,0 +1,57 @@
+#![no_std]
+#![no_main]
+
+use core::cell::RefCell;
+
+use embassy_executor::Spawner;
+use embassy_nrf::gpio::{Level, Output, OutputDrive};
+use embassy_nrf::interrupt;
+use embassy_nrf::rtc::Rtc;
+use embassy_sync::blocking_mutex::raw::CriticalSectionRawMutex;
+use embassy_sync::blocking_mutex::Mutex;
+use portable_atomic::AtomicU64;
+use {defmt_rtt as _, panic_probe as _};
+
+// 64 bit counter which will never overflow.
+static TICK_COUNTER: AtomicU64 = AtomicU64::new(0);
+static RTC: Mutex<CriticalSectionRawMutex, RefCell<Option<Rtc<'static, embassy_nrf::peripherals::RTC0>>>> =
+    Mutex::new(RefCell::new(None));
+
+#[embassy_executor::main]
+async fn main(_spawner: Spawner) {
+    defmt::println!("nRF52840 RTC example");
+    let p = embassy_nrf::init(Default::default());
+    let mut led = Output::new(p.P0_13, Level::High, OutputDrive::Standard);
+    // Counter resolution is 125 ms.
+    let mut rtc = Rtc::new(p.RTC0, (1 << 12) - 1).unwrap();
+    rtc.enable_interrupt(embassy_nrf::rtc::Interrupt::Tick, true);
+    rtc.enable_event(embassy_nrf::rtc::Interrupt::Tick);
+    rtc.enable();
+    RTC.lock(|r| {
+        let mut rtc_borrow = r.borrow_mut();
+        *rtc_borrow = Some(rtc);
+    });
+
+    let mut last_counter_val = 0;
+    loop {
+        let current = TICK_COUNTER.load(core::sync::atomic::Ordering::Relaxed);
+        if current != last_counter_val {
+            led.toggle();
+            last_counter_val = current;
+        }
+    }
+}
+
+#[interrupt]
+fn RTC0() {
+    // For 64-bit, we do not need to worry about overflowing, at least not for realistic program
+    // lifetimes.
+    TICK_COUNTER.fetch_add(1, core::sync::atomic::Ordering::Relaxed);
+    RTC.lock(|r| {
+        let mut rtc_borrow = r.borrow_mut();
+        rtc_borrow
+            .as_mut()
+            .unwrap()
+            .reset_event(embassy_nrf::rtc::Interrupt::Tick);
+    });
+}
-- 
cgit