redo time.monotonic() to avoid double precision

dhalbert · tannewt · commit a1409d1432ea · 2017-10-17T10:02:16.000-07:00
diff --git a/shared-bindings/time/__init__.c b/shared-bindings/time/__init__.c
@@ -52,7 +52,9 @@
 //|   :rtype: float
 //|
 STATIC mp_obj_t time_monotonic(void) {
-    return mp_obj_new_float(common_hal_time_monotonic() / 1000.0);
+    uint64_t time64 = common_hal_time_monotonic();
+    // 4294967296 = 2^32
+    return mp_obj_new_float(((uint32_t) (time64 >> 32) * 4294967296.0f + (uint32_t) (time64 & 0xffffffff)) / 1000.0f);
 }
 MP_DEFINE_CONST_FUN_OBJ_0(time_monotonic_obj, time_monotonic);
 
