Measure the BEC voltage on boards with a BEC input

docs/Battery.md

@@ -70,6 +70,14 @@ set vbat_warning_cell_voltage = 340
 set vbat_min_cell_voltage = 330
 ```
 
+## BEC voltage
+
+The BEC supplies the servo rail, which on these boards also powers the flight controller. When it sags under a servo load, the board can reset or the servos glitch, so it is worth watching apart from the pack.
+
+The NEXUS, the NEXUS X/XR, the Vantac RF007 and the FlyDragon Pro measure the servo rail on their own ADC, on PC1, as Rotorflight does for the same boards. On the FlyDragon Pro that is the servo plug bank; PC2, the output of its built-in regulator, is not read. `bec_adc_channel` selects the channel, PC1's by default, and `vbec_scale` calibrates it as `vbat_scale` does the pack.
+
+`status` in the CLI shows it. The OSD element "BEC voltage" shows it, and blinks below `vbec_warning_voltage` (0.01 V units, 0 for no warning).
+
 # Current Monitoring
 
 Current monitoring (amperage) is supported by connecting a current meter to the appropriate current meter ADC input (see the documentation for your particular board).

docs/Settings.md

@@ -591,6 +591,16 @@ If the remaining battery capacity goes below this threshold the beeper will emit
 
 ---
 
+### bec_adc_channel
+
+ADC channel measuring the BEC voltage, on the servo rail the BEC supplies. Defaults to the board's input for it. 0 = none
+
+| Default | Min | Max |
+| --- | --- | --- |
+| _target default_ | ADC_CHN_NONE | ADC_CHN_MAX |
+
+---
+
 ### beeper_pwm_mode
 
 Allows disabling PWM mode for beeper on some targets. Switch from ON to OFF if the external beeper sound is weak. Do not switch from OFF to ON without checking if the board supports PWM beeper mode
@@ -7472,6 +7482,26 @@ Warning voltage per cell, this triggers battery-warning alarms, in 0.01V units,
 
 ---
 
+### vbec_scale
+
+BEC voltage calibration value, as vbat_scale: 1100 = 11:1 voltage divider (10k:1k) x 100. Adjust it if the BEC voltage shown by "status" in the CLI differs from a multimeter's reading
+
+| Default | Min | Max |
+| --- | --- | --- |
+| _target default_ | 0 | 5000 |
+
+---
+
+### vbec_warning_voltage
+
+Below this BEC voltage the OSD's BEC element blinks [0.01V]. 0 = no warning
+
+| Default | Min | Max |
+| --- | --- | --- |
+| 0 | 0 | 1500 |
+
+---
+
 ### vtol_autotransition_always
 
 When enabled, an armed manual VTOL profile switch between a multicopter-like profile and a fixed-wing profile starts the auto-transition controller instead of switching profiles directly. This allows a two-position desired-mode switch: selecting FW starts MC->FW, selecting MC starts FW->MC. Disarmed direct profile switching remains available for bench and preflight checks. OFF preserves direct manual profile switching when `MIXER TRANSITION` is not active. Available only on targets with more than 512 KB flash.

docs/development/msp/README.md

@@ -3215,8 +3215,9 @@ When the MSP JSON specification changes, bump `msp_messages.json` version:
 | `remainingCapacity` | `uint32_t` | 4 | Capacity unit (`batteryMetersConfig()->capacity_unit`) | Estimated remaining capacity (`getBatteryRemainingCapacity()`) |
 | `percentageRemaining` | `uint8_t` | 1 | % | Estimated remaining capacity percentage (`calculateBatteryPercentage()`) |
 | `rssi` | `uint16_t` | 2 | Raw (0-1023) | RSSI value (`getRSSI()`) |
+| `becVoltage` | `uint16_t` | 2 | 0.01V | BEC voltage (`becGetVoltage()`) on boards with a BEC input; 0xFFFF on the others, and with `bec_adc_channel` = 0 |
 
-**Notes:** Requires `USE_CURRENT_METER`/`USE_ADC` for current-related fields; values fall back to zero when unavailable. Capacity fields are reported in the units configured by `batteryMetersConfig()->capacity_unit` (mAh or mWh).
+**Notes:** Requires `USE_CURRENT_METER`/`USE_ADC` for current-related fields; values fall back to zero when unavailable. Capacity fields are reported in the units configured by `batteryMetersConfig()->capacity_unit` (mAh or mWh). Older firmware ends after `rssi`.
 
 ## <a id="msp2_inav_misc"></a>`MSP2_INAV_MISC (8195 / 0x2003)`
 **Description:** Retrieves miscellaneous configuration settings, superseding `MSP_MISC` with higher precision and capacity fields.  

docs/development/msp/msp_messages.json

@@ -6995,10 +6995,16 @@
                         "ctype": "uint16_t",
                         "desc": "RSSI value (`getRSSI()`)",
                         "units": "Raw (0-1023)"
+                    },
+                    {
+                        "name": "becVoltage",
+                        "ctype": "uint16_t",
+                        "desc": "BEC voltage (`becGetVoltage()`) on boards with a BEC input; 0xFFFF on the others, and with `bec_adc_channel` = 0",
+                        "units": "0.01V"
                     }
                 ]
             },
-            "notes": "Requires `USE_CURRENT_METER`/`USE_ADC` for current-related fields; values fall back to zero when unavailable. Capacity fields are reported in the units configured by `batteryMetersConfig()->capacity_unit` (mAh or mWh).",
+            "notes": "Requires `USE_CURRENT_METER`/`USE_ADC` for current-related fields; values fall back to zero when unavailable. Capacity fields are reported in the units configured by `batteryMetersConfig()->capacity_unit` (mAh or mWh). Older firmware ends after `rssi`.",
             "description": "Provides detailed analog sensor readings, superseding `MSP_ANALOG` with higher precision and additional fields."
         },
         "MSP2_INAV_MISC": {

src/main/CMakeLists.txt

@@ -501,6 +501,8 @@ main_sources(COMMON_SRC
     sensors/battery_config_structs.h
     sensors/battery_sensor_dronecan.c
     sensors/battery_sensor_dronecan.h
+    sensors/bec.c
+    sensors/bec.h
     sensors/boardalignment.c
     sensors/boardalignment.h
     sensors/compass.c

src/main/config/parameter_group_ids.h

@@ -136,7 +136,8 @@
 #define PG_DRONECAN_CONFIG 1045
 #define PG_TERRAIN_NAV_CONFIG 1046
 #define PG_DRONECAN_DNA_SERVER 1047     // Separate PG so we don't wipe user settings if the allocation table changes
-#define PG_INAV_END PG_DRONECAN_DNA_SERVER
+#define PG_BEC_CONFIG 1049
+#define PG_INAV_END PG_BEC_CONFIG
 
 // OSD configuration (subject to change)
 //#define PG_OSD_FONT_CONFIG 2047

src/main/drivers/adc.h

@@ -17,16 +17,24 @@
 
 #pragma once
 
+// ADC_FUNCTION_COUNT depends on the target's USE_BEC_VOLTAGE
+#include "platform.h"
+
 #include "drivers/io_types.h"
 
 typedef enum {
     ADC_BATTERY = 0,
     ADC_RSSI = 1,
     ADC_CURRENT = 2,
     ADC_AIRSPEED = 3,
+#ifdef USE_BEC_VOLTAGE
+    ADC_BEC = 4,
+#endif
     ADC_FUNCTION_COUNT
 } adcFunction_e;
 
+#define ADCVREF 3300    // mV
+
 typedef enum {
     ADC_CHN_NONE = 0,
     ADC_CHN_1 = 1,

src/main/fc/cli.c

@@ -116,6 +116,7 @@ bool cliMode = false;
 #include "sensors/acceleration.h"
 #include "sensors/barometer.h"
 #include "sensors/battery.h"
+#include "sensors/bec.h"
 #include "sensors/boardalignment.h"
 #include "sensors/compass.h"
 #include "sensors/diagnostics.h"
@@ -4155,6 +4156,11 @@ static void cliStatus(char *cmdline)
     dateTimeFormatLocal(buf, &dt);
     cliPrintLinef("Current Time: %s", buf);
     cliPrintLinef("Voltage: %d.%02dV (%dS battery - %s)", getBatteryVoltage() / 100, getBatteryVoltage() % 100, getBatteryCellCount(), getBatteryStateString());
+#ifdef USE_BEC_VOLTAGE
+    if (becIsConfigured()) {
+        cliPrintLinef("BEC: %d.%02dV", becGetVoltage() / 100, becGetVoltage() % 100);
+    }
+#endif
     cliPrintf("CPU Clock=%dMHz", (SystemCoreClock / 1000000));
 
     const uint32_t detectedSensorsMask = sensorsMask();
@@ -4251,7 +4257,13 @@ static void cliStatus(char *cmdline)
     cliPrintLinef("I2C Errors: %d, config size: %d, max available config: %d", i2cErrorCounter, getEEPROMConfigSize(), &__config_end - &__config_start);
 #endif
 #if defined(USE_ADC) && !defined(SITL_BUILD)
-    static char * adcFunctions[] = { "BATTERY", "RSSI", "CURRENT", "AIRSPEED" };
+    static char * adcFunctions[] = {
+        "BATTERY", "RSSI", "CURRENT", "AIRSPEED",
+#ifdef USE_BEC_VOLTAGE
+        "BEC",
+#endif
+    };
+    STATIC_ASSERT(ARRAYLEN(adcFunctions) == ADC_FUNCTION_COUNT, adc_function_names);
     cliPrintLine("ADC channel usage:");
     for (int i = 0; i < ADC_FUNCTION_COUNT; i++) {
         cliPrintf("  %8s :", adcFunctions[i]);

src/main/fc/config.c

@@ -147,14 +147,22 @@ PG_RESET_TEMPLATE(beeperConfig_t, beeperConfig,
                   .pwmMode = SETTING_BEEPER_PWM_MODE_DEFAULT,
 );
 
+#ifdef USE_BEC_VOLTAGE
+// The BEC input grows the group: a board gaining it starts again from the target's channels
+PG_REGISTER_WITH_RESET_TEMPLATE(adcChannelConfig_t, adcChannelConfig, PG_ADC_CHANNEL_CONFIG, 1);
+#else
 PG_REGISTER_WITH_RESET_TEMPLATE(adcChannelConfig_t, adcChannelConfig, PG_ADC_CHANNEL_CONFIG, 0);
+#endif
 
 PG_RESET_TEMPLATE(adcChannelConfig_t, adcChannelConfig,
     .adcFunctionChannel = {
         [ADC_BATTERY]   = VBAT_ADC_CHANNEL,
         [ADC_RSSI]      = RSSI_ADC_CHANNEL,
         [ADC_CURRENT]   = CURRENT_METER_ADC_CHANNEL,
         [ADC_AIRSPEED]  = AIRSPEED_ADC_CHANNEL,
+#ifdef USE_BEC_VOLTAGE
+        [ADC_BEC]       = BEC_ADC_CHANNEL,
+#endif
     }
 );
 

src/main/fc/fc_init.c

@@ -520,6 +520,10 @@ void init(void)
     }
 #endif
 
+#ifdef USE_BEC_VOLTAGE
+    adc_params.adcFunctionChannel[ADC_BEC] = adcChannelConfig()->adcFunctionChannel[ADC_BEC];
+#endif
+
     adcInit(&adc_params);
 #endif
 

src/main/fc/fc_msp.c

@@ -130,6 +130,7 @@
 #include "sensors/sensors.h"
 #include "sensors/diagnostics.h"
 #include "sensors/battery.h"
+#include "sensors/bec.h"
 #include "sensors/rangefinder.h"
 #include "sensors/acceleration.h"
 #include "sensors/barometer.h"
@@ -812,6 +813,11 @@ static bool mspFcProcessOutCommand(uint16_t cmdMSP, sbuf_t *dst, mspPostProcessF
         sbufWriteU32(dst, getBatteryRemainingCapacity());
         sbufWriteU8(dst, calculateBatteryPercentage());
         sbufWriteU16(dst, getRSSI());
+#ifdef USE_BEC_VOLTAGE
+        sbufWriteU16(dst, becIsConfigured() ? becGetVoltage() : 0xFFFF);
+#else
+        sbufWriteU16(dst, 0xFFFF);
+#endif
         break;
 
     case MSP2_INAV_GET_LINK_STATS:

src/main/fc/fc_tasks.c

@@ -88,6 +88,7 @@
 #include "sensors/temperature.h"
 #include "sensors/barometer.h"
 #include "sensors/battery.h"
+#include "sensors/bec.h"
 #include "sensors/compass.h"
 #include "sensors/gyro.h"
 #include "sensors/irlock.h"
@@ -155,6 +156,10 @@ void taskUpdateBattery(timeUs_t currentTimeUs)
     }
 #endif
 
+#ifdef USE_BEC_VOLTAGE
+    becUpdate(BatMonitoringTimeSinceLastServiced);
+#endif
+
     batMonitoringLastServiced = currentTimeUs;
 }
 
@@ -398,7 +403,11 @@ void fcTasksInit(void)
 #ifdef USE_LIGHTS
     setTaskEnabled(TASK_LIGHTS, true);
 #endif
-    setTaskEnabled(TASK_BATTERY, feature(FEATURE_VBAT) || isAmperageConfigured());
+    bool batteryTask = feature(FEATURE_VBAT) || isAmperageConfigured();
+#ifdef USE_BEC_VOLTAGE
+    batteryTask = batteryTask || becIsConfigured();
+#endif
+    setTaskEnabled(TASK_BATTERY, batteryTask);
     setTaskEnabled(TASK_TEMPERATURE, true);
     setTaskEnabled(TASK_RX, true);
 #ifdef USE_GPS

src/main/fc/settings.yaml

@@ -470,6 +470,31 @@ groups:
         field: adcFunctionChannel[ADC_AIRSPEED]
         min: ADC_CHN_NONE
         max: ADC_CHN_MAX
+      - name: bec_adc_channel
+        description: "ADC channel measuring the BEC voltage, on the servo rail the BEC supplies. Defaults to the board's input for it. 0 = none"
+        default_value: :target
+        field: adcFunctionChannel[ADC_BEC]
+        condition: USE_BEC_VOLTAGE
+        min: ADC_CHN_NONE
+        max: ADC_CHN_MAX
+
+  - name: PG_BEC_CONFIG
+    type: becConfig_t
+    headers: ["sensors/bec.h"]
+    condition: USE_BEC_VOLTAGE
+    members:
+      - name: vbec_scale
+        description: "BEC voltage calibration value, as vbat_scale: 1100 = 11:1 voltage divider (10k:1k) x 100. Adjust it if the BEC voltage shown by \"status\" in the CLI differs from a multimeter's reading"
+        default_value: :target
+        field: scale
+        min: 0
+        max: 5000
+      - name: vbec_warning_voltage
+        description: "Below this BEC voltage the OSD's BEC element blinks [0.01V]. 0 = no warning"
+        default_value: 0
+        field: warningVoltage
+        min: 0
+        max: 1500
 
   - name: PG_ACCELEROMETER_CONFIG
     type: accelerometerConfig_t

src/main/io/osd.c

@@ -109,6 +109,7 @@
 
 #include "sensors/acceleration.h"
 #include "sensors/battery.h"
+#include "sensors/bec.h"
 #include "sensors/boardalignment.h"
 #include "sensors/compass.h"
 #include "sensors/diagnostics.h"
@@ -238,7 +239,7 @@ static bool osdDisplayHasCanvas;
 #define AH_MAX_PITCH_DEFAULT 20 // Specify default maximum AHI pitch value displayed (degrees)
 
 PG_REGISTER_WITH_RESET_TEMPLATE(osdConfig_t, osdConfig, PG_OSD_CONFIG, 0);
-PG_REGISTER_WITH_RESET_FN(osdLayoutsConfig_t, osdLayoutsConfig, PG_OSD_LAYOUTS_CONFIG, 4);
+PG_REGISTER_WITH_RESET_FN(osdLayoutsConfig_t, osdLayoutsConfig, PG_OSD_LAYOUTS_CONFIG, 5);
 
 /* OSD formatting helpers replacing common tfp_sprintf patterns
  * for reduced code size and CPU overhead. */
@@ -1864,6 +1865,22 @@ static bool osdDrawSingleElement(uint8_t item)
             2 + osdConfig()->main_voltage_decimals, osdConfig()->main_voltage_decimals);
         return true;
 
+#ifdef USE_BEC_VOLTAGE
+    case OSD_BEC_VOLTAGE:
+        strcpy(buff, "BEC");
+        if (!becIsConfigured()) {
+            strcpy(buff + 3, " ---");
+        } else {
+            osdFormatCentiNumber(buff + 3, becGetVoltage(), 0, 2, 0, 4, false);
+            if (becIsVoltageLow()) {
+                TEXT_ATTRIBUTES_ADD_BLINK(elemAttr);
+            }
+        }
+        buff[7] = SYM_VOLT;
+        buff[8] = '\0';
+        break;
+#endif
+
     case OSD_CURRENT_DRAW: {
         osdFormatCentiNumber(buff, getAmperage(), 0, 2, 0, 3, false);
         buff[3] = SYM_AMP;

src/main/io/osd.h

@@ -382,6 +382,7 @@ typedef enum {
     OSD_GPS_EXTRA_STATS,
     OSD_AUTO_SPEED,  // 170
     OSD_TERRAIN_AGL, // 171,
+    OSD_BEC_VOLTAGE = 173, // 172 is the MZTC camera's (#11837), which the Configurator already has
     OSD_ITEM_COUNT // MUST BE LAST
 } osd_items_e;
 

src/main/sensors/battery.c

@@ -80,8 +80,6 @@ static ina226Dev_t ina226Dev;
 static bool ina226Detected = false;
 #endif
 
-#define ADCVREF 3300                            // in mV (3300 = 3.3V)
-
 #define VBATT_CELL_FULL_MAX_DIFF 10             // Max difference with cell max voltage for the battery to be considered full (10mV steps)
 #define VBATT_PRESENT_THRESHOLD 220             // Minimum voltage to consider battery present
 #define VBATT_STABLE_DELAY 40                   // Delay after connecting battery to begin monitoring