Diff: Clock.cpp

Revision:

2:75a5b58b2338

--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/Clock.cpp	Mon Mar 25 07:35:02 2019 +0000
@@ -0,0 +1,65 @@
+#include <mbed.h>
+ 
+// The us ticker is a wrapping uint32_t. We insert interrupts at
+// 0, 0x40000000, 0x8000000, and 0xC0000000, rather than just 0 or just 0xFFFFFFFF because there is
+// code that calls interrupts that are "very soon" immediately and we don't
+// want that. Also because if we only use 0 and 0x80000000 then there is a chance it would
+// be considered to be in the past and executed immediately.
+ 
+class ExtendedClock : public TimerEvent
+{
+public:
+    ExtendedClock()
+    {
+        // This also starts the us ticker.
+        mTriggers = 0;
+        insert(0x40000000);
+    }
+ 
+    float read()
+    {
+        return read_us() / 1000000.0f;
+    }
+ 
+    uint64_t read_ms()
+    {
+        return read_us() / 1000;
+    }
+ 
+    uint64_t read_us()
+    {
+        return mTriggers * 0x40000000ull + (ticker_read(_ticker_data) & 0x3FFFFFFF);
+    }
+ 
+private:
+    void handler() 
+    {
+        ++mTriggers;
+        // If this is the first time we've been called (at 0x4...)
+        // then mTriggers now equals 1 and we want to insert at 0x80000000.
+        insert((mTriggers+1) * 0x40000000);
+    }
+ 
+    // The number of times the us_ticker has rolled over.
+    uint32_t mTriggers;
+};
+ 
+static ExtendedClock _GlobalClock;
+ 
+// Return the number of seconds since boot.
+float clock_s()
+{
+    return _GlobalClock.read();
+}
+ 
+// Return the number of milliseconds since boot.
+uint64_t clock_ms()
+{
+    return _GlobalClock.read_ms();
+}
+ 
+// Return the number of microseconds since boot.
+uint64_t clock_us()
+{
+    return _GlobalClock.read_us();
+}
\ No newline at end of file