From 303c9f183f8456edea52ab17f513f4acc8a2df4c Mon Sep 17 00:00:00 2001
From: Matt Knight <mattnite@protonmail.com>
Date: Thu, 7 Jul 2022 21:38:40 -0700
Subject: [PATCH] add busy sleep functions

---
 src/hal.zig      |  1 +
 src/hal/time.zig | 44 ++++++++++++++++++++++++++++++++++++++++++++
 2 files changed, 45 insertions(+)
 create mode 100644 src/hal/time.zig

diff --git a/src/hal.zig b/src/hal.zig
index ae181da..1a793b1 100644
--- a/src/hal.zig
+++ b/src/hal.zig
@@ -3,6 +3,7 @@ const regs = microzig.chip.regsisters;
 pub const gpio = @import("hal/gpio.zig");
 pub const clocks = @import("hal/clocks.zig");
 pub const multicore = @import("hal/multicore.zig");
+pub const time = @import("hal/time.zig");
 
 pub const default_clock_config = clocks.GlobalConfiguration.init(.{
     //.ref = .{ .source = .src_xosc },
diff --git a/src/hal/time.zig b/src/hal/time.zig
new file mode 100644
index 0000000..2ed49ae
--- /dev/null
+++ b/src/hal/time.zig
@@ -0,0 +1,44 @@
+const microzig = @import("microzig");
+const TIMER = microzig.chip.registers.TIMER;
+
+pub const Absolute = struct {
+    us_since_boot: u64,
+};
+
+pub fn getTimeSinceBoot() Absolute {
+    var high_word = TIMER.TIMERAWH.*;
+
+    return while (true) {
+        var low_word = TIMER.TIMERAWL.*;
+        const next_high_word = TIMER.TIMERAWH.*;
+        if (next_high_word == high_word)
+            break Absolute{
+                .us_since_boot = @intCast(u64, high_word) << 32 | low_word,
+            };
+
+        high_word = next_high_word;
+    } else unreachable;
+}
+
+pub fn makeTimeoutUs(timeout_us: u64) Absolute {
+    return Absolute{
+        .us_since_boot = getTimeSinceBoot().us_since_boot + timeout_us,
+    };
+}
+
+pub fn reached(time: Absolute) bool {
+    const now = getTimeSinceBoot();
+    return now.us_since_boot >= time.us_since_boot;
+}
+
+pub fn sleepMs(time_ms: u32) void {
+    sleepUs(time_ms * 1000);
+}
+
+pub fn sleepUs(time_us: u64) void {
+    const end_time = Absolute{
+        .us_since_boot = time_us + getTimeSinceBoot().us_since_boot,
+    };
+
+    while (!reached(end_time)) {}
+}