Fall back to default modem preset if requested bandwidth is too large (#4497)

src/mesh/RadioInterface.cpp

@@ -412,6 +412,8 @@ void RadioInterface::applyModemConfig()
     // Set up default configuration
     // No Sync Words in LORA mode
     meshtastic_Config_LoRaConfig &loraConfig = config.lora;
+    bool validConfig = false; // We need to check for a valid configuration
+    while (!validConfig) {
         if (loraConfig.use_preset) {
 
             switch (loraConfig.modem_preset) {
@@ -480,6 +482,25 @@ void RadioInterface::applyModemConfig()
                 bw = 1625.0;
         }
 
+        if ((myRegion->freqEnd - myRegion->freqStart) < bw / 1000) {
+            static const char *err_string =
+                "Regional frequency range is smaller than bandwidth. Falling back to default preset.\n";
+            LOG_ERROR(err_string);
+            RECORD_CRITICALERROR(meshtastic_CriticalErrorCode_INVALID_RADIO_SETTING);
+
+            meshtastic_ClientNotification *cn = clientNotificationPool.allocZeroed();
+            cn->level = meshtastic_LogRecord_Level_ERROR;
+            sprintf(cn->message, err_string);
+            service->sendClientNotification(cn);
+
+            // Set to default modem preset
+            loraConfig.use_preset = true;
+            loraConfig.modem_preset = meshtastic_Config_LoRaConfig_ModemPreset_LONG_FAST;
+        } else {
+            validConfig = true;
+        }
+    }
+
     power = loraConfig.tx_power;
 
     if ((power == 0) || ((power + REGULATORY_GAIN_LORA > myRegion->powerLimit) && !devicestate.owner.is_licensed))

src/mesh/RadioInterface.h

@@ -5,6 +5,7 @@
 #include "Observer.h"
 #include "PointerQueue.h"
 #include "airtime.h"
+#include "error.h"
 
 #define MAX_TX_QUEUE 16 // max number of packets which can be waiting for transmission