common: Add the systick module.

[gps-watch.git] / src / common / systick.rs

diff --git a/src/common/systick.rs b/src/common/systick.rs
new file mode 100644 (file)
index 0000000..78730d3
--- /dev/null
+++ b/src/common/systick.rs
@@ -0,0 +1,76 @@
+/*
+ * Copyright (c) 2019 Tilman Sauerbeck (tilman at code-monkey de)
+ *
+ * Permission is hereby granted, free of charge, to any person obtaining
+ * a copy of this software and associated documentation files (the
+ * "Software"), to deal in the Software without restriction, including
+ * without limitation the rights to use, copy, modify, merge, publish,
+ * distribute, sublicense, and/or sell copies of the Software, and to
+ * permit persons to whom the Software is furnished to do so, subject to
+ * the following conditions:
+ *
+ * The above copyright notice and this permission notice shall be
+ * included in all copies or substantial portions of the Software.
+ *
+ * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND,
+ * EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF
+ * MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND
+ * NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE
+ * LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION
+ * OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION
+ * WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.
+ */
+
+use register;
+
+type Reg32 = register::Register<u32>;
+
+const SYSTICK_BASE: u32 = 0xe000e010;
+
+const SYSTICK_CTRL: u32 = SYSTICK_BASE + 0x00;
+const SYSTICK_LOAD: u32 = SYSTICK_BASE + 0x04;
+const SYSTICK_VAL : u32 = SYSTICK_BASE + 0x08;
+
+pub const RESOLUTION_MS : u32 = 10;
+
+extern {
+    fn get_ticks() -> u32;
+}
+
+pub fn init() {
+    // Assuming a 48 MHz core clock.
+    let ticks = 48000000 / 1000 * RESOLUTION_MS;
+
+    let mut load = Reg32::new(SYSTICK_LOAD);
+    load.write(ticks - 1);
+
+    let mut val = Reg32::new(SYSTICK_VAL);
+    val.write(0);
+
+    let mut ctrl = Reg32::new(SYSTICK_CTRL);
+    ctrl.write(7);
+}
+
+pub fn now() -> u32 {
+    unsafe {
+        get_ticks()
+    }
+}
+
+pub fn delay_ms(timeout_ms: u32) {
+    let timeout_ticks = timeout_ms / RESOLUTION_MS;
+    let start_ticks = now();
+
+    while (now() - start_ticks) < timeout_ticks {
+    }
+}
+
+pub fn has_timeout_ms(start_ticks: u32, timeout_ms: u32) -> bool {
+    let timeout_ticks = timeout_ms / RESOLUTION_MS;
+
+    (now() - start_ticks) >= timeout_ticks
+}
+
+pub fn elapsed_ms(later_ticks: u32, earlier_ticks: u32) -> u32 {
+    (later_ticks - earlier_ticks) * RESOLUTION_MS
+}