MCP9808: Add perf_count for comms errors and prevent publishing nan temp values.

src/drivers/temperature_sensor/mcp9808/mcp9808.h

@@ -70,6 +70,8 @@ private:
 
 	uORB::PublicationMulti<sensor_temp_s> _to_sensor_temp{ORB_ID(sensor_temp)};
 	perf_counter_t _cycle_perf;
+	perf_counter_t _comms_errors;
+
 
 	sensor_temp_s _sensor_temp{};
 

src/drivers/temperature_sensor/mcp9808/mcp9808_main.cpp

@@ -44,7 +44,9 @@
 MCP9808::MCP9808(const I2CSPIDriverConfig &config) :
 	I2C(config),
 	I2CSPIDriver(config),
-	_cycle_perf(perf_alloc(PC_ELAPSED, MODULE_NAME": single-sample"))
+	_cycle_perf(perf_alloc(PC_ELAPSED, MODULE_NAME": single-sample")),
+	_comms_errors(perf_alloc(PC_COUNT, MODULE_NAME": comms errors"))
+
 {
 	_sensor_temp.device_id = this->get_device_id();
 
@@ -54,6 +56,8 @@ MCP9808::~MCP9808()
 {
 	ScheduleClear();
 	perf_free(_cycle_perf);
+	perf_free(_comms_errors);
+
 }
 
 void MCP9808::exit_and_cleanup()
@@ -71,6 +75,12 @@ void MCP9808::RunImpl()
 		measurement_time = hrt_absolute_time(); // get the time the measurement was taken
 		float temperature = read_temperature();
 
+		if (std::isnan(temperature)) {
+
+			perf_count(_comms_errors);
+
+		} else {
+
 			_sensor_temp.timestamp = hrt_absolute_time();
 			_sensor_temp.timestamp_sample = measurement_time;
 			_sensor_temp.temperature = temperature;
@@ -78,6 +88,9 @@ void MCP9808::RunImpl()
 			_to_sensor_temp.publish(_sensor_temp);
 		}
 
+
+	}
+
 	perf_end(_cycle_perf);
 }
 
@@ -95,6 +108,8 @@ void MCP9808::print_status()
 {
 	I2CSPIDriverBase::print_status();
 	perf_print_counter(_cycle_perf);
+	perf_print_counter(_comms_errors);
+
 }
 
 extern "C" int mcp9808_main(int argc, char *argv[])