Initial code for flowmeter

MK/module/flowmeter/flowmeter.cpp

+volatile byte flowrate_pulsecount;  
+float flowrate;
+unsigned int flowml;
+static millis_t flowmeter_timer = 0;
+
+
+void flow_init() {
+
+   flowrate = 0;
+   pulsecount = 0;
+   flowml = 0;
+   pinMode(FLOWMETER_PIN, INPUT);
+   
+   attachInterrupt(FLOWMETER_INTERRUPT, flowrate_pulsecounter, FALLING);
+}
+
+void flowrate_manage() {
+   millis_t = now;
+   now = millis()
+   if(ELAPSED(now, flowmeter_timer) {
+      detachInterrupt(FLOWMETER_INTERRUPT);
+      flowrate  = ((1000.0 / (now - flowmeter_timer)) * flowrate_pulsecount) / FLOWMETER_CALIBRATION;
+      flowmeter_timer = now + 1000UL;
+      flowml = (flowrate / 60) * 1000;
+
+      pulseCount = 0;
+      attachInterrupt(FLOWMETER_INTERRUPT, flowrate_pulsecounter,, FALLING);
+   }
+
+}
+
+void flowrate_pulsecounter()
+{
+  // Increment the pulse counter
+  flowrate_pulsecount++;
+}
+
+
+