Add bidirectional list navigation with UP/DOWN keys (issue #145)

App/app/action.c

@@ -236,7 +236,7 @@ void ACTION_Scan(bool bRestart)
         }
 
         // channel mode. Keep scanning but toggle between scan lists
-        RADIO_NextValidList();
+        RADIO_NextValidList(1);
 
         #ifdef ENABLE_FEAT_F4HWN_RESUME_STATE
             SETTINGS_WriteCurrentState();

App/app/chFrScanner.c

@@ -55,7 +55,7 @@ void CHFRSCANNER_Start(const bool storeBackupSettings, const int8_t scan_directi
     {   
 
         if(!RADIO_CheckValidList(gEeprom.SCAN_LIST_DEFAULT)) {
-            RADIO_NextValidList();
+            RADIO_NextValidList(1);
         }
 
         // channel mode

App/app/main.c

@@ -291,16 +291,25 @@ static void processFKeyFunction(const KEY_Code_t Key, const bool beep)
 
 #ifdef ENABLE_FEAT_F4HWN // Set Squelch F + UP or Down and Step F + SIDE1 or F + SIDE2
         case KEY_UP:
-            gEeprom.SQUELCH_LEVEL = (gEeprom.SQUELCH_LEVEL < 9) ? gEeprom.SQUELCH_LEVEL + 1: 9;
-            gVfoConfigureMode     = VFO_CONFIGURE;
-            gWasFKeyPressed = false;
-            break;
         case KEY_DOWN:
-            gEeprom.SQUELCH_LEVEL = (gEeprom.SQUELCH_LEVEL > 0) ? gEeprom.SQUELCH_LEVEL - 1: 0;
-            gVfoConfigureMode     = VFO_CONFIGURE;
-            gWasFKeyPressed = false;
-            break;
+            {
+                int8_t direction = (Key == KEY_UP) ? 1 : -1;
 
+                if (gScanStateDir != SCAN_OFF) {
+                    RADIO_NextValidList(direction);
+                } else {
+                    // Adjust squelch: UP increments, DOWN decrements
+                    if (direction > 0) {
+                        gEeprom.SQUELCH_LEVEL = (gEeprom.SQUELCH_LEVEL < 9) ? gEeprom.SQUELCH_LEVEL + 1 : 9;
+                    } else {
+                        gEeprom.SQUELCH_LEVEL = (gEeprom.SQUELCH_LEVEL > 0) ? gEeprom.SQUELCH_LEVEL - 1 : 0;
+                    }
+                    gVfoConfigureMode = VFO_CONFIGURE;
+                }
+
+                gWasFKeyPressed = false;
+            }
+            break;
         case KEY_SIDE1:
             uint8_t a = FREQUENCY_GetSortedIdxFromStepIdx(gTxVfo->STEP_SETTING);
             if (a < STEP_N_ELEM - 1)
@@ -496,7 +505,7 @@ static void MAIN_Key_DIGITS(KEY_Code_t Key, bool bKeyPressed, bool bKeyHeld)
                     /* Requested scan list is empty or invalid:
                        jump to the next valid scan list */
                     gEeprom.SCAN_LIST_DEFAULT = value;
-                    RADIO_NextValidList();
+                    RADIO_NextValidList(1);
                 }
 
             #ifdef ENABLE_FEAT_F4HWN_RESUME_STATE

App/radio.c

@@ -102,28 +102,30 @@ bool RADIO_CheckValidList(uint8_t scanList)
     return false;
 }
 
-void RADIO_NextValidList(void)
+void RADIO_NextValidList(int8_t direction)
 {
     uint8_t startList = gEeprom.SCAN_LIST_DEFAULT;
     uint8_t attempts = 0;
-    const uint8_t MAX_LISTS = MR_CHANNELS_LIST + 2;  // 1-25, includes ALL
+    const uint8_t MAX_VALUE = MR_CHANNELS_LIST + 1;  // 25 (1-24 lists + ALL)
     
     do {
-        // Move to next scan list, wrapping around from 25 to 1
-        gEeprom.SCAN_LIST_DEFAULT = ((gEeprom.SCAN_LIST_DEFAULT + 1) % MAX_LISTS) ?: 1;
+        if (direction > 0) {
+            // Forward: 1 → 2 → ... → 25 → 1
+            gEeprom.SCAN_LIST_DEFAULT = (gEeprom.SCAN_LIST_DEFAULT % MAX_VALUE) + 1;
+        } else {
+            // Backward: 25 → 24 → ... → 1 → 25
+            gEeprom.SCAN_LIST_DEFAULT = ((gEeprom.SCAN_LIST_DEFAULT - 2 + MAX_VALUE) % MAX_VALUE) + 1;
+        }
         attempts++;
         
-        // Check if current list has valid channels
         if (RADIO_CheckValidList(gEeprom.SCAN_LIST_DEFAULT))
             return;
             
-    // Stop if we've cycled through all lists or made too many attempts
-    } while (gEeprom.SCAN_LIST_DEFAULT != startList && attempts < MAX_LISTS);
+    } while (gEeprom.SCAN_LIST_DEFAULT != startList && attempts < MAX_VALUE);
     
-    // Safety fallback: if no valid list found, switch to ALL mode
-    // This prevents infinite loops and ensures scanning can continue
+    // Safety fallback: switch to ALL mode
     if (!RADIO_CheckValidList(gEeprom.SCAN_LIST_DEFAULT)) {
-        gEeprom.SCAN_LIST_DEFAULT = MR_CHANNELS_LIST + 1;  // ALL
+        gEeprom.SCAN_LIST_DEFAULT = MAX_VALUE;  // ALL (25)
     }
 }
 

App/radio.h

@@ -149,7 +149,7 @@ extern DCS_CodeType_t gCurrentCodeType;
 extern VfoState_t     VfoState[2];
 
 bool     RADIO_CheckValidList(uint8_t scanList);
-void     RADIO_NextValidList(void);
+void     RADIO_NextValidList(int8_t direction);
 bool     RADIO_CheckValidChannel(uint16_t channel, bool checkScanList, uint8_t scanList);
 uint16_t RADIO_FindNextChannel(uint16_t ChNum, int8_t Direction, bool bCheckScanList, uint8_t RadioNum);
 void     RADIO_InitInfo(VFO_Info_t *pInfo, const uint16_t ChannelSave, const uint32_t Frequency);