begin adding sd.Card refactor

sd/timer.go

@@ -0,0 +1,22 @@
+package sd
+
+import (
+	"time"
+)
+
+var timeoutTimer [2]timer
+
+type timer struct {
+	start   int64
+	timeout int64
+}
+
+func setTimeout(timerID int, timeout time.Duration) *timer {
+	timeoutTimer[timerID].start = time.Now().UnixNano()
+	timeoutTimer[timerID].timeout = timeout.Nanoseconds()
+	return &timeoutTimer[timerID]
+}
+
+func (t timer) expired() bool {
+	return time.Now().UnixNano() > (t.start + t.timeout)
+}