battery_status: do not publish if no voltage channel is defined

This is the case for boards with digital readout, like v5x, but still
enable the battery_status module for external analog driver options.

An alternative would be to not run battery_status depending on config.

platforms/common/include/px4_platform_common/board_common.h

@@ -145,7 +145,10 @@
 #  define BOARD_BATT_I_LIST       {ADC_BATTERY_CURRENT_CHANNEL}
 #  define BOARD_BRICK_VALID_LIST  {BOARD_ADC_BRICK_VALID}
 #elif BOARD_NUMBER_BRICKS == 2
-#  if  !defined(BOARD_NUMBER_DIGITAL_BRICKS)
+#  if  defined(BOARD_NUMBER_DIGITAL_BRICKS)
+#    define BOARD_BATT_V_LIST       {-1, -1}
+#    define BOARD_BATT_I_LIST       {-1, -1}
+#  else
 #    define BOARD_BATT_V_LIST       {ADC_BATTERY1_VOLTAGE_CHANNEL, ADC_BATTERY2_VOLTAGE_CHANNEL}
 #    define BOARD_BATT_I_LIST       {ADC_BATTERY1_CURRENT_CHANNEL, ADC_BATTERY2_CURRENT_CHANNEL}
 #  endif

src/modules/battery_status/analog_battery.cpp

@@ -41,12 +41,11 @@
 static constexpr int   DEFAULT_V_CHANNEL[BOARD_NUMBER_BRICKS] = BOARD_BATT_V_LIST;
 static constexpr int   DEFAULT_I_CHANNEL[BOARD_NUMBER_BRICKS] = BOARD_BATT_I_LIST;
 #else
-static constexpr int   DEFAULT_V_CHANNEL[BOARD_NUMBER_BRICKS] = {0};
-static constexpr int   DEFAULT_I_CHANNEL[BOARD_NUMBER_BRICKS] = {0};
+#error  "BOARD_BATT_V_LIST and BOARD_BATT_I_LIST need to be defined"
 #endif
 #else
-static constexpr int DEFAULT_V_CHANNEL[1] = {0};
-static constexpr int DEFAULT_I_CHANNEL[1] = {0};
+static constexpr int DEFAULT_V_CHANNEL[1] = {-1};
+static constexpr int DEFAULT_I_CHANNEL[1] = {-1};
 #endif
 
 AnalogBattery::AnalogBattery(int index, ModuleParams *parent, const int sample_interval_us, const uint8_t source,

src/modules/battery_status/battery_status.cpp

@@ -177,6 +177,7 @@ BatteryStatus::adc_poll()
 	/* Per Brick readings with default unread channels at 0 */
 	float bat_current_adc_readings[BOARD_NUMBER_BRICKS] {};
 	float bat_voltage_adc_readings[BOARD_NUMBER_BRICKS] {};
+	bool has_bat_voltage_adc_channel[BOARD_NUMBER_BRICKS] {};
 
 	int selected_source = -1;
 
@@ -201,23 +202,27 @@ BatteryStatus::adc_poll()
 
 				/* look for specific channels and process the raw voltage to measurement data */
 
+				if (adc_report.channel_id[i] >= 0) {
 					if (adc_report.channel_id[i] == _analogBatteries[b]->get_voltage_channel()) {
 						/* Voltage in volts */
 						bat_voltage_adc_readings[b] = adc_report.raw_data[i] *
 									      adc_report.v_ref /
 									      adc_report.resolution;
+						has_bat_voltage_adc_channel[b] = true;
 
 					} else if (adc_report.channel_id[i] == _analogBatteries[b]->get_current_channel()) {
 						bat_current_adc_readings[b] = adc_report.raw_data[i] *
 									      adc_report.v_ref /
 									      adc_report.resolution;
 					}
+				}
 
 			}
 		}
 
 		for (int b = 0; b < BOARD_NUMBER_BRICKS; b++) {
 
+			if (has_bat_voltage_adc_channel[b]) { // Do not publish if no voltage channel configured
 				_analogBatteries[b]->updateBatteryStatusADC(
 					hrt_absolute_time(),
 					bat_voltage_adc_readings[b],
@@ -225,6 +230,7 @@ BatteryStatus::adc_poll()
 				);
 			}
 		}
+	}
 }
 
 void