implement timer counter

rp2040-hal/src/timer.rs

@@ -1,3 +1,24 @@
-//! Timers
+//! Timer Peripheral
 // See [Chapter 4 Section 6](https://datasheets.raspberrypi.org/rp2040/rp2040_datasheet.pdf) for more details
-// TODO
+
+use crate::pac::TIMER;
+
+/// Timer peripheral
+pub struct Timer {
+    timer: TIMER,
+}
+
+impl Timer {
+    /// Create a new [`Timer`]
+    pub fn new(timer: TIMER) -> Self {
+        Self { timer }
+    }
+
+    /// Get the current counter value.
+    pub fn get_counter(&self) -> u64 {
+        // latched read, low before high
+        let lo = self.timer.timelr.read().bits();
+        let hi = self.timer.timehr.read().bits();
+        (hi as u64) << 32 | lo as u64
+    }
+}