Refactor race condition free timer helper (#850)

* Implement half_period_counter in rtic-time

* Rename compute_now to calculate_now, use it in stm32 and imxrt

* Add more tests

* Add some docs

* Fix clippy warning, add imxrt timer to monotonics tests

* Bump dependency version to make sure monotonics will build properly

* Add changelog to rtic-monotonics

* Add more docs

* Add more docs

* Finish documentation

* Fix typos

* Switch from atomic-polyfill to portable-atomic

* Some more doc fixes

* More doc fixes

* Minor doc fix

* Minor doc fix

* Fix Atomics not existing

* Fix example

* Minor example improvement

* Revert back to atomic-polyfill

* Fix cargo.toml formatting

* Remove atomic-polyfill

* Attempt to fix unused macro warning

* Remove atomics completely from half period counter

* Minor doc fix

* Doc fixes

* Doc fixes

* Remove obsolete comment

* Fix ordering in monotonic initialization sequence

1 files changed, 95 insertions, 0 deletions

diff --git a/rtic-time/tests/half_period_time_counter.rs b/rtic-time/tests/half_period_time_counter.rs
new file mode 100644
index 0000000..ceffbea
--- /dev/null
+++ b/rtic-time/tests/half_period_time_counter.rs
@@ -0,0 +1,95 @@
+use rtic_time::half_period_counter::calculate_now;
+
+macro_rules! do_test_u8 {
+    ($periods:literal, $counter:literal, $expected:literal) => {{
+        let periods: u32 = $periods;
+        let counter: u8 = $counter;
+        let expected: u32 = $expected;
+        let actual: u32 = calculate_now(periods, || counter);
+        assert_eq!(
+            actual, expected,
+            "Expected: ({} | {}) => {}, got: {}",
+            periods, counter, expected, actual
+        );
+    }};
+}
+
+macro_rules! do_test_u16 {
+    ($periods:literal, $counter:literal, $expected:literal) => {{
+        let periods: u16 = $periods;
+        let counter: u16 = $counter;
+        let expected: u32 = $expected;
+        let actual: u32 = calculate_now(periods, || counter);
+        assert_eq!(
+            actual, expected,
+            "Expected: ({} | {}) => {}, got: {}",
+            periods, counter, expected, actual
+        );
+    }};
+}
+
+#[test]
+fn half_period_time_counter_u8() {
+    do_test_u8!(0, 0, 0);
+    do_test_u8!(0, 1, 1);
+
+    do_test_u8!(0, 126, 126);
+    do_test_u8!(1, 126, 382); // This is why it's important to load the periods before the counter
+    do_test_u8!(0, 127, 127);
+    do_test_u8!(1, 127, 383);
+    do_test_u8!(0, 128, 128);
+    do_test_u8!(1, 128, 128);
+    do_test_u8!(0, 129, 129);
+    do_test_u8!(1, 129, 129);
+
+    do_test_u8!(1, 254, 254);
+    do_test_u8!(2, 254, 510);
+    do_test_u8!(1, 255, 255);
+    do_test_u8!(2, 255, 511);
+    do_test_u8!(1, 0, 256);
+    do_test_u8!(2, 0, 256);
+    do_test_u8!(1, 1, 257);
+    do_test_u8!(2, 1, 257);
+
+    do_test_u8!(2, 126, 382);
+    do_test_u8!(3, 126, 638);
+    do_test_u8!(2, 127, 383);
+    do_test_u8!(3, 127, 639);
+    do_test_u8!(2, 128, 384);
+    do_test_u8!(3, 128, 384);
+    do_test_u8!(2, 129, 385);
+    do_test_u8!(3, 129, 385);
+}
+
+#[test]
+fn half_period_time_counter_u16() {
+    do_test_u16!(0, 0, 0);
+    do_test_u16!(0, 1, 1);
+
+    do_test_u16!(0, 32766, 32766);
+    do_test_u16!(1, 32766, 98302); // This is why it's important to load the periods before the counter
+    do_test_u16!(0, 32767, 32767);
+    do_test_u16!(1, 32767, 98303);
+    do_test_u16!(0, 32768, 32768);
+    do_test_u16!(1, 32768, 32768);
+    do_test_u16!(0, 32769, 32769);
+    do_test_u16!(1, 32769, 32769);
+
+    do_test_u16!(1, 65534, 65534);
+    do_test_u16!(2, 65534, 131070);
+    do_test_u16!(1, 65535, 65535);
+    do_test_u16!(2, 65535, 131071);
+    do_test_u16!(1, 0, 65536);
+    do_test_u16!(2, 0, 65536);
+    do_test_u16!(1, 1, 65537);
+    do_test_u16!(2, 1, 65537);
+
+    do_test_u16!(2, 32766, 98302);
+    do_test_u16!(3, 32766, 163838);
+    do_test_u16!(2, 32767, 98303);
+    do_test_u16!(3, 32767, 163839);
+    do_test_u16!(2, 32768, 98304);
+    do_test_u16!(3, 32768, 98304);
+    do_test_u16!(2, 32769, 98305);
+    do_test_u16!(3, 32769, 98305);
+}