ADSB CPA calculation

Author: error414

.gitignore

@@ -46,3 +46,14 @@ launch.json
 # Assitnow token and files for test script
 tokens.yaml
 *.ubx
+/testing/
+/.idea/.gitignore
+/.idea/.name
+/.idea/cmake.xml
+/.idea/editor.xml
+/.idea/inav.iml
+/.idea/runConfigurations/MatekH743.xml
+/.idea/misc.xml
+/.idea/modules.xml
+/.idea/vcs.xml
+/.idea/workspace.xml

docs/ADSB.md

@@ -63,3 +63,41 @@ AT+SETTINGS=SAVE
 * in INAV configurator ports TAB set telemetry MAVLINK, and baudrate 115200
 * https://pantsforbirds.com/adsbee-1090/quick-start/
 
+---
+
+---
+
+## Alert and Warning
+The ADS-B warning/alert system supports two operating modes, controlled by the parameter adsb_calculation_use_cpa (ON or OFF).
+
+---
+
+### ADS-B Warning and Alert Messages (CPA Mode OFF)
+The ADS-B warning/alert system supports two operating modes, controlled by the parameter **adsb_calculation_use_cpa** (ON or OFF).
+
+When **adsb_calculation_use_cpa = OFF**, the system evaluates only the **current distance between the aircraft and the UAV**. The aircraft with the **shortest distance** is always selected for monitoring.
+
+- If the aircraft enters the **warning zone** (`adsb_distance_warning`), the corresponding **OSD element is displayed**.
+- If the aircraft enters the **alert zone** (`adsb_distance_alert`), the **OSD element starts blinking**, indicating a higher-priority alert.
+
+This mode therefore provides a simple proximity-based warning determined purely by real-time distance.
+
+---
+
+### ADS-B Warning and Alert Messages (CPA Mode ON)
+
+When **adsb_calculation_use_cpa = ON**, the system evaluates aircraft using the **Closest Point of Approach (CPA)** and predicted trajectories, not only the current distance.
+
+1. **Aircraft already inside the alert zone**  
+   If one or more aircraft are currently inside the **alert zone** (`adsb_distance_alert`), the **closest aircraft** to the UAV is selected and the **OSD element blinks**.
+
+2. **Aircraft in the warning zone, none predicted to enter the alert zone**  
+   If aircraft are present in the **warning zone** (`adsb_distance_warning`), but none of them are predicted to enter the **alert zone** (their CPA distance is greater than `adsb_distance_alert`), the **closest aircraft to the UAV** is selected and the **OSD element remains steady** (no blinking).
+
+3. **Aircraft in the warning zone, one predicted to enter the alert zone**  
+   If at least one aircraft in the **warning zone** is predicted to enter the **alert zone**, that aircraft is selected and the **OSD element blinks**.
+
+4. **Aircraft in the warning zone, multiple predicted to enter the alert zone**  
+   If multiple aircraft are predicted to enter the **alert zone**, the system selects the aircraft that will **reach the alert zone first**, and the **OSD element blinks**.
+
+![ADSB CPA_ON](assets/images/adsb-CPA-on.png)

docs/assets/images/adsb-CPA-on.png

@@ -358,6 +358,7 @@ main_sources(COMMON_SRC
     flight/adaptive_filter.h
 
     io/adsb.c
+    io/adsb.h
     io/beeper.c
     io/beeper.h
     io/servo_sbus.c

src/main/CMakeLists.txt

@@ -187,14 +187,6 @@ void taskUpdateCompass(timeUs_t currentTimeUs)
 }
 #endif
 
-#ifdef USE_ADSB
-void taskAdsb(timeUs_t currentTimeUs)
-{
-    UNUSED(currentTimeUs);
-    adsbTtlClean(currentTimeUs);
-}
-#endif
-
 #ifdef USE_BARO
 void taskUpdateBaro(timeUs_t currentTimeUs)
 {
@@ -554,7 +546,7 @@ cfTask_t cfTasks[TASK_COUNT] = {
         [TASK_ADSB] = {
         .taskName = "ADSB",
         .taskFunc = taskAdsb,
-        .desiredPeriod = TASK_PERIOD_HZ(1),      // ADSB is updated at 1 Hz
+        .desiredPeriod = TASK_PERIOD_MS(500),      // ADSB is updated at 1 Hz
         .staticPriority = TASK_PRIORITY_IDLE,
     },
 #endif

src/main/fc/fc_tasks.c

@@ -3677,6 +3677,12 @@ groups:
         field: adsb_warning_style
         type: uint8_t
         condition: USE_ADSB
+      - name: osd_adsb_calculation_use_cpa
+        description: "Use CPA (Closest Point of Approach) method for ADS-B traffic distance and collision risk calculation instead of instantaneous distance."
+        default_value: OFF
+        field: adsb_calculation_use_cpa
+        type: bool
+        condition: USE_ADSB
       - name: osd_estimations_wind_compensation
         description: "Use wind estimation for remaining flight time/distance estimation"
         default_value: ON