control flag indicating bms is present, timeout

Set control flag to 1 if a BMS is present, so user interface can
enable/disable functionality.

add timeout so that a lost BMS eventually causes relay signals to
operate.

delegates/dvcc.py

@@ -20,6 +20,7 @@
 # message, so the update rate could be increased. For now, keep this at 3 and
 # above.
 ADJUST = 3
+BMS_TIMEOUT = 60
 
 VEBUS_FIRMWARE_REQUIRED = 0x422
 VEDIRECT_FIRMWARE_REQUIRED = 0x129
@@ -610,6 +611,7 @@ def __init__(self, sc):
 		self._vecan_services = []
 		self._timer = None
 		self._tickcount = ADJUST
+		self._bmscount = BMS_TIMEOUT
 
 	def get_input(self):
 		return [
@@ -668,6 +670,7 @@ def set_sources(self, dbusmonitor, settings, dbusservice):
 		self._dbusservice.add_path('/Control/EffectiveChargeVoltage', value=None)
 		self._dbusservice.add_path('/Control/BmsParameters', value=0)
 		self._dbusservice.add_path('/Control/MaxChargeCurrent', value=0)
+		self._dbusservice.add_path('/Control/BmsPresent', value=0)
 		self._dbusservice.add_path('/Control/Dvcc', value=1)
 		self._dbusservice.add_path('/Debug/BatteryOperationalLimits/SolarVoltageOffset', value=0, writeable=True)
 		self._dbusservice.add_path('/Debug/BatteryOperationalLimits/VebusVoltageOffset', value=0, writeable=True)
@@ -736,13 +739,21 @@ def bms(self):
 		return None
 
 	def _on_timer(self):
+		from delegates import RelayState
 		bol_support = self.has_dvcc
 		bms_service = self.bms
 
 		# Toggle relays if so configured. Do this early because we want
 		# this to work even if DVCC is off.
-		if bms_service is not None:
-			from delegates import RelayState
+		if bms_service is None:
+			self._bmscount = max(self._bmscount - 1, 0)
+			if not self._bmscount:
+				self._dbusservice['/Control/BmsPresent'] = 0
+				RelayState.instance.set_function(RelayState.FUNCTION_BMS_STOPCHARGE, 1)
+				RelayState.instance.set_function(RelayState.FUNCTION_BMS_STOPDISCHARGE, 1)
+		else:
+			self._bmscount = BMS_TIMEOUT
+			self._dbusservice['/Control/BmsPresent'] = 1
 			RelayState.instance.set_function(
 				RelayState.FUNCTION_BMS_STOPCHARGE, int(bms_service.maxchargecurrent == 0))
 			RelayState.instance.set_function(